Articles de revues : « Ground-state CO molecules »

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Blokland, Janneke H., Jens Riedel, Stephan Putzke, Boris G. Sartakov, Gerrit C. Groenenboom et Gerard Meijer. « Producing translationally cold, ground-state CO molecules ». Journal of Chemical Physics 135, n^o 11 (21 septembre 2011) : 114201. http://dx.doi.org/10.1063/1.3637037.

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Huang Yun-Xia, Xu Shu-Wu et Yang Xiao-Hua. « Orientation of ground-state CO (X1∑+) molecules by combined electrostatic and laser fields ». Acta Physica Sinica 61, n^o 24 (2012) : 243701. http://dx.doi.org/10.7498/aps.61.243701.

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ZHU, JUN, XIU-RONG ZHANG, PEI-YING HUO et ZHI-CHENG YU. « STRUCTURE STABILITY AND ELECTRONIC PROPERTIES OF CumConCO (m+n=2–7) CLUSTERS ». Surface Review and Letters 24, n^o 04 (25 août 2016) : 1750049. http://dx.doi.org/10.1142/s0218625x17500494.

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The structure stability and electronic properties of CumConCO ([Formula: see text]–7) clusters have been systematically investigated using density functional theory (DFT) within the generalized gradient approximation (GGA). The results indicate that the ground state structures of CumConCO clusters obtained by adsorbing CO molecules on the top sites of stable CumConclusters with C atoms and CO molecules have been activated during adsorption process. Cu2CO, CuCoCO, Cu3CoCO, Co4CO, Cu4CoCO and Cu3Co3CO clusters are stronger than other ground state clusters in thermodynamic stability. Cu2CO, Cu4CO and Cu6CO clusters show stronger chemical stability; Co2CO, Co4CO, Cu5CoCO, Cu3Co3CO, Cu2Co5CO and Co7CO clusters show better propensity to adsorb CO for these clusters have larger adsorption energies; Electronic states of Cu2Co3CO, CuCo4CO, Co5CO, Cu4Co3CO, Cu3Co4CO, CuCo6CO and Co7CO clusters are mainly influenced by those of 3d orbitals in Co and Cu atoms, the contribution to total magnetic moments of these clusters comes mainly from Co atoms and these clusters have high magnetism.

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Chen, Li, Jascha A. Lau, Dirk Schwarzer, Jörg Meyer, Varun B. Verma et Alec M. Wodtke. « The Sommerfeld ground-wave limit for a molecule adsorbed at a surface ». Science 363, n^o 6423 (13 décembre 2018) : 158–61. http://dx.doi.org/10.1126/science.aav4278.

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Using a mid-infrared emission spectrometer based on a superconducting nanowire single-photon detector, we observed the dynamics of vibrational energy pooling of carbon monoxide (CO) adsorbed at the surface of a sodium chloride (NaCl) crystal. After exciting a majority of the CO molecules to their first vibrationally excited state (v = 1), we observed infrared emission from states up to v = 27. Kinetic Monte Carlo simulations showed that vibrational energy collects in a few CO molecules at the expense of those up to eight lattice sites away by selective excitation of NaCl’s transverse phonons. The vibrating CO molecules behave like classical oscillating dipoles, losing their energy to NaCl lattice vibrations via the electromagnetic near-field. This is analogous to Sommerfeld’s description of radio transmission along Earth’s surface by ground waves.

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Al-Othman, A. B., et A. S. Sandouqa. « Comparison study of bound states for diatomic molecules using Kratzer, Morse, and modified Morse potentials ». Physica Scripta 97, n^o 3 (15 février 2022) : 035401. http://dx.doi.org/10.1088/1402-4896/ac514c.

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Abstract In this paper, the bound-state energy eigenvalues for several diatomic molecules (O2, I2, N2, H2, CO, NO, LiH, HCl) are computed for various quantum numbers using the shifted 1/N expansion method with the Kratzer, Morse and Modified Morse potentials. Numerical results of the energy eigenvalues for the selected diatomic molecules are discussed. Our results for energy eigenvalues agree perfectly with the results obtained in the literature. A comparative study is performed for four diatomic molecules (H2, N2, CO and HCl) in their ground states using the three potentials.

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Gaume, Ralph A. « The Ground State Hydroxyl Masers Associated with OH 340.78–0.10 ». Symposium - International Astronomical Union 129 (1988) : 251–52. http://dx.doi.org/10.1017/s007418090013459x.

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The dynamics of the molecular envelopes surrounding ultracompact H II regions has been the subject of much debate. Since the envelopes often exhibit molecular line emission, line observations have been the primary method of probing these circumstellar shells. The existence of expansive motions in the molecular clouds surrounding massive newly formed stars has been firmly established. Proper motion studies of galactic water masers indicate general expansion, whereas high resolution CO studies often show collimated bipolar outflows centered on continuum H II regions. Maps of the OH maser emission, often associated with these regions, show the masers scattered, apparently randomly, in both position and velocity across an area a few arcseconds in size. Typical velocity ranges for the associated OH maser emission are on the order of 10 km s−1. A number of models of the dynamical and physical conditions of the masing envelope have been developed to explain the properties of specific regions, e.g., collapsing remnant accretion envelopes, rotating disks or tori of neutral material, and expanding shells of shocked material. There is evidence from comparing the velocities of the OH masers to that of recombination lines associated with the underlying H II regions that in most sources the OH masers are formed in material still accreting toward the central object (Garay et al., 1985) (however see Welch and Marr, 1986). Mirabel et al., 1986, have reported the detection of (thermal and subthermal) high velocity OH outflow in several regions of star formation, demonstrating that OH molecules, at least in some instances, are also involved in collimated flows from central stellar objects.

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Li, Xiaohong, Bocheng Ding, Yunfei Feng, Ruichang Wu, Lifang Tian, Jianye Huang et Xiaojing Liu. « High Energy Inner Shell Photoelectron Diffraction in CO₂ ». Chinese Physics Letters 39, n^o 3 (1 mars 2022) : 033401. http://dx.doi.org/10.1088/0256-307x/39/3/033401.

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Photoelectron diffraction is an effective tool to probe the structures of molecules. The higher the photoelectron kinetic energy is, the higher order the diffraction pattern is disclosed in. Up to date, either the multi-atomic molecule with the photoelectron kinetic energy below 150 eV or the diatomic molecule with 735 eV photoelectron has been experimentally reported. In this study, we measured the diffraction pattern of C 1s and O 1s photoelectrons in CO2 with 319.7 and 433.5 eV kinetic energies, respectively. The extracted C–O bond lengths are longer than the C–O bond length at the ground state, which is attributed to the asymmetric fragmentation that preferentially occurs at the longer chemical bond side during the zero-energy asymmetric vibration.

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Klein, Hans-Friedrich, Alexandra Brand et Gerhard Cordier. « Synthesis and Reactions with CO and C2H4 of Cobalt(I) Complexes Containing Trimethylphosphine and Chelating o-Diphenylphosphanyl- phenolate Ligands ». Zeitschrift für Naturforschung B 53, n^o 3 (1 mars 1998) : 307–14. http://dx.doi.org/10.1515/znb-1998-0309.

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Abstract In tetracoordinate cobalt(I) halide compounds CoX(Ph2P⌒O H)(PMe3)2 (X = CI, Br) o-phos-phanylphenols PhaP⌒OH are coordinated as phosphane ligands. In the presence of base chelat ing anions Ph2P⌒O- give rise to pentacoordinate com plexes Co(Ph2P⌒O)(PMe3)3. Molecular structures are presented for both types of compounds. The five-membered chelate ring in Co(Ph2P⌒O)(PMe3)3 is resistant to protonation, and ring-opening is not observed in the presence of CO or C2H4. Replacing one of the trimethylphosphanes by one of the π-acceptor ligands affords fluxional complex molecules which upon cooling attain definite ground-state geometries out of a multitude of possible isomers.

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Harvey, Pierre D., Marielle Crozet et Khin T. Aye. « Photoinduced addition of dioxygen molecules in the unsaturated sites of the Pd3(dppm)3CO2+ catalyst ». Canadian Journal of Chemistry 73, n^o 1 (1 janvier 1995) : 123–30. http://dx.doi.org/10.1139/v95-019.

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The photoinduced addition of O2 onto the unsaturated cluster Pd3(dppm)3CO2+ (as a CF3CO2− salt) in acetonitrile is reported. The final product Pd3(dppm)3(O2)22+(v(O2) = 838 and 866 cm−1) is formed in a multi-step fashion in which two photochemical intermediates are observed (presumably Pd3(dppm)3(O2)(CO)2+ and Pd3(dppm)3(O2)2+. No X-ray structure could be obtained, but numerous spectroscopic findings demonstrate that O2 binds the Pd3 center as a peroxo-O2, and acts as a two-electron donor that triply bridges the metal atoms (forming a 44-electron cluster). The very small excited state lifetimes (between 25 and 35 ± 10 ps) obtained by picosecond flash photolysis indicate that the primary photoreaction is unimolecular, and demonstrate that the first photochemically added O2 molecule must be preassembled in the excited state prior to any photoinduced transformation. This [Formula: see text] ground state complex is responsible for the photoinduced production of the bisdioxygen compound and can be observed by UV–visible spectroscopy. The low efficiency of the photoreaction (quantum yield (Φ) = 0.033 ± 0.004) is explained by the very short excited state lifetime at 298 K, and the competition of O2 with solvent molecules to occupy the unsaturated site of the empty cavity in Pd3(dppm)3CO2+ (i.e., ground state guest–host chemistry). The binding constant for O2 with Pd3(dppm)3CO2+ is roughly estimated to range between 1 and 730 M−1 in the ground state and is considered to be weak. Keywords: clusters, photochemistry, guest–host, oxidation, dioxygen.

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Wakabayashi, Tomonari, Urszula Szczepaniak, Kaito Tanaka, Satomi Saito, Keisuke Fukumoto, Riku Ohnishi, Kazunori Ozaki et al. « Phosphorescence of Hydrogen-Capped Linear Polyyne Molecules C8H2, C10H2 and C12H2 in Solid Hexane Matrices at 20 K ». Photochem 2, n^o 1 (28 février 2022) : 181–201. http://dx.doi.org/10.3390/photochem2010014.

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Laser-ablated polyyne molecules, H(C≡C)nH, were separated by size in solutions and co-condensed with excess hexane molecules at a cryogenic temperature of 20 K in a vacuum system. The solid matrix samples containing C8H2, C10H2, and C12H2 molecules were irradiated with UV laser pulses and the phosphorescence 0–0 band was observed at 532, 605, and 659 nm, respectively. Vibrational progression was observed for the symmetric stretching mode of the carbon chain in the ground state with increments of ~2190 cm−1 for C8H2, ~2120 cm−1 for C10H2, and ~2090 cm−1 for C12H2. Temporal decay analysis of the phosphorescence intensity revealed the lifetimes of the triplet state as ~30 ms for C8H2, ~8 ms for C10H2, and ~4 ms for C12H2. The phosphorescence excitation spectrum reproduces UV absorption spectra in the hexane solution and in the gas phase at ambient temperature, although the excitation energy was redshifted. The symmetry-forbidden vibronic transitions were observed for C10H2 by lower excitation energies of 25,500–31,000 cm−1 (320–390 nm). Detailed phosphorescence excitation patterns are discussed along the interaction of the polyyne molecule and solvent molecules of hexane.

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Samant, R., S. U. Lotliker et A. M. Desai. « Comments on the paper ‘Comparison study of bound states for diatomic molecules using Kratzer, Morse, and modified Morse potentials’ ». Physica Scripta 98, n^o 2 (13 janvier 2023) : 027002. http://dx.doi.org/10.1088/1402-4896/acaa66.

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Abstract Al-Othman et al (2022, Phys. Scr. 97 035401) in their paper have compared the energy eigenvalues obtained using Kratzer, Morse, and modified Morse potentials for four diatomic molecules (H2, N2, CO, and HCl) using the shifted 1/N expansion method. We show that due to the wrong expression of the parameter used in the modified Morse potential, the energy eigenvalues obtained for the case of modified Morse potential are incorrect, and the interpretation of the results stated in this paper is not reliable. We have rectified the error and recalculated the vibrational energy eigenvalues for the ground state of the HCl molecule using the shifted 1/N expansion method and compared the accuracy of Kratzer, Morse, and modified Morse with that of the observed vibrational energy eigenvalues. Also, we have determined the energy eigenvalues for the ground state of the HCl molecule by numerically solving the Schrödinger equation for the case of the modified Morse potential and compared the accuracy with the values obtained using the shifted 1/N expansion method. The vibrational energy eigenvalues obtained using modified Morse for the HCl molecule are found to be closer to the observed values than the Morse and Kratzer potential functions.

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Krstić, Marjan, Karin Fink et Dmitry I. Sharapa. « The Adsorption of Small Molecules on the Copper Paddle-Wheel : Influence of the Multi-Reference Ground State ». Molecules 27, n^o 3 (28 janvier 2022) : 912. http://dx.doi.org/10.3390/molecules27030912.

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We report a theoretical study of the adsorption of a set of small molecules (C2H2, CO, CO2, O2, H2O, CH3OH, C2H5OH) on the metal centers of the “copper paddle-wheel”—a key structural motif of many MOFs. A systematic comparison between DFT of different rungs, single-reference post-HF methods (MP2, SOS–MP2, MP3, DLPNO–CCSD(T)), and multi-reference approaches (CASSCF, DCD–CAS(2), NEVPT2) is performed in order to find a methodology that correctly describes the complicated electronic structure of paddle-wheel structure together with a reasonable description of non-covalent interactions. Apart from comparison with literature data (experimental values wherever possible), benchmark calculations with DLPNO–MR–CCSD were also performed. Despite tested methods show qualitative agreement in the majority of cases, we showed and discussed reasons for quantitative differences as well as more fundamental problems of specific cases.

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Weldeab, Asmerom O., Cory T. Kornman, Lei Li, Daken J. Starkenburg, Xueying Zhao, Danielle E. Fagnani, Sara J. Sadovy, Scott S. Perry, Jiangeng Xue et Ronald K. Castellano. « Structure–Assembly–Property Relationships of Simple Ditopic Hydrogen-Bonding-Capable π-Conjugated Oligomers ». Organic Materials 03, n^o 02 (avril 2021) : 302–16. http://dx.doi.org/10.1055/a-1534-1508.

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A series of simple ditopic hydrogen-bonding-capable molecules functionalized with 2,4-diamino-1,3,5-triazine (DAT), barbiturate (B), and phthalhydrazide (PH) on both termini of a 2,2′-bithiophene linker were designed and synthesized. The intrinsic electronic structures of the ditopic DAT, PH, and B molecules were investigated with ground-state density functional theory calculations. Their solution absorbance was investigated with UV-vis, where it was found that increasing size of R group substituents on the bithiophene linker resulted in a general blue-shift in solution absorbance maximum. The solid-state optical properties of ditopic DAT and B thin films were evaluated by UV-vis, and it was found that the solid-state absorbance was red-shifted with respect to solution absorbance in all cases. The three DAT molecules were vacuum-thermal-deposited onto Au(111) substrates and the morphologies were examined using scanning tunneling microscopy. (DAT-T)2 was observed to organize into six-membered rosettes on the surface, whereas (DAT-TMe)2 formed linear assemblies before and after thermal annealing. For (DAT-Toct)2 , an irregular arrangement was observed, while (B-TMe)2 showed several co-existent assembly patterns. The work presented here provides fundamental molecular–supramolecular relationships useful for semiconductive materials design based on ditopic hydrogen-bonding-capable building blocks.

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Hu, Chang Sheng, Jun Zhang, Hong Fei Yan et Jin Xin He. « Thermodynamic Analysis of a Brown Glass Containing Fe, C and S ». Advanced Materials Research 591-593 (novembre 2012) : 973–76. http://dx.doi.org/10.4028/www.scientific.net/amr.591-593.973.

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The ground state geometrical of cyclic sulfur molecules S8 has been studied with RHF/6-311G* of ab initio methods. Gibbs free energy of CO, SO2, S8 and CO2 from 300 to 1673K has been calculated using ab initio method. Besides, the reaction free enthalpies were calculated. The results show that resultants of reaction of CO and SO2 are S8 and CO2 below 1451K and the reaction is spontaneous.Fe2O3 in glass can is reduced into FeO whose redox number is negative. The Gibbs free energy of FeO is smaller than that of FeS while chemical stability of FeO is higher than that of FeS. Structures of cycle sulfur are versatile. Bond energy of S8, S12 and S18 is broken, which need high energy. When small sulfur ring molecules be formed, the chemical and heat stability of S8 are improved.

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Amovilli, C., N. H. March, T. G�l et �. Nagy. « Force-balance and differential equation for the ground-state electron density in atoms and molecules ». International Journal of Quantum Chemistry 77, n^o 4 (2000) : 716–20. http://dx.doi.org/10.1002/(sici)1097-461x(2000)77:4<716 ::aid-qua4>3.0.co;2-c.

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Hohn, Frauke, Heinrich Billetter, Ingo Pantenburg et Uwe Ruschewitz. « Ni(C2(COO)2)(H2O)4 · 2 H2O und Ni(C2(COO)2)(H2O)2 : zwei Koordinationspolymere mit dem Acetylendicarboxylat-Dianion / Ni(C2(COO)2)(H2O)4 · 2 H2O and Ni(C2 (COO)2)(H2O)2 : Two Co-ordination Polymers of the Acetylenedicarboxylate Dianion ». Zeitschrift für Naturforschung B 57, n^o 12 (1 décembre 2002) : 1375–81. http://dx.doi.org/10.1515/znb-2002-1206.

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From a solution of Ni(CH3COO)2 ∙ 4 H2O and acetylenedicarboxylic acid in deionized water single crystals of Ni(C2(COO)2)(H2O)4 ∙ 2 H2O(P21/a, Z = 2, isotypic to Co(C2(COO)2)(H2O)4 ∙ 2 H2O) were obtained by slow evaporation of the solvent. In the solid state structure nickel is octahedrally surrounded by four water molecules and two oxygen atoms of the carboxylate anions. These octahedra are connected to chains by the dicarboxylates. Heating the hexahydrate to 100 °C in a stream of argon leads to Ni(C2(COO)2)(H2O)2 (C2/c, Z = 4, isotypic to Mn[C2(COO)2] ∙ 2 H2O). Here, the NiO6 octahedron is built by two water molecules and four oxygen atoms of the dicarboxylate ligands, which connect the Ni octahedra to a three-dimensional network. Thermoanalytical investigations show another mass loss at about 200 °C, which leads to non-crystalline products. Finally, at about 400 °C NiO is formed. Measurements of the magnetic susceptibilities result in the expected behaviour for Ni2+ in an octahedral co-ordination (3A2 ground state). The effective magnetic moment at room temperature is μeff = 3.20 μB.

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SONG, PENG, YONG-HUA ZHU, JIAN-YONG LIU et FENG-CAI MA. « THE STEREODYNAMICS STUDY OF THE C(3P) + OH (X2 Π) → CO(X1Σ+) + H(2S) REACTION ». Journal of Theoretical and Computational Chemistry 09, n^o 05 (octobre 2010) : 935–43. http://dx.doi.org/10.1142/s0219633610006109.

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The stereodynamics of the title reaction on the ground electronic state X2A' potential energy surface (PES)1 has been studied using the quasiclassical trajectory (QCT) method. The commonly used polarization-dependent differential cross-sections (PDDCSs) of the product and the angular momentum alignment distribution, P(θr) and P(Φr), are generated in the center-of-mass frame using QCT method to gain insight of the alignment and orientation of the product molecules. Influence of collision energy on the stereodynamics is shown and discussed. The results reveal that the distribution of P(θr) and P(Φr) is sensitive to collision energy. The PDDCSs exhibit different collision energy dependency relationship at low and high collision energy ranges.

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TAN, JIAO-JIE, CE HAO, NING-NING WEI, MING-XING ZHANG et XI-YANG DAI. « TIME-DEPENDENT DENSITY FUNCTIONAL THEORY STUDY ON THE ELECTRONIC EXCITED-STATE HYDROGEN BONDING DYNAMICS OF METHYL ACETATE IN AQUEOUS SOLUTION ». Journal of Theoretical and Computational Chemistry 10, n^o 03 (juin 2011) : 393–400. http://dx.doi.org/10.1142/s0219633611006529.

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The time-dependent density functional theory (TDDFT) method has been carried out to investigate the hydrogen-bonding dynamics of methyl acetate ( CH 3 CO 2 CH 3) in hydrogen-donating water solvent. The ground-state geometry optimizations, electronic transition energies and corresponding oscillation strengths of the low-lying electronically-excited states for the isolated CH 3 CO 2 CH 3 and H2O monomers, the hydrogen-bonded CH3CO2CH3-(H2O)1, 2 complexes have been calculated using DFT and TDDFT methods respectively. One intermolecular hydrogen bond C=O⋯H–O is formed between CH3CO2CH3 and one water molecule in CH3CO2CH3-H2O dimer. Meanwhile, in CH3CO2CH3-(H2O)2 trimer, two intermolecular hydrogen bonds C=O⋯H–O are formed between CH3CO2CH3 and two water molecules. By theoretically monitoring the excitation energy changes among the CH3CO2CH3 monomer, the CH3CO2CH3-H2O dimer, and the CH3CO2CH3-(H2O)2 trimer, we have demonstrated interestingly that in some electronically-excited states, the intermolecular hydrogen bonds are strengthened inducing electronic spectral redshifts, while in others weakened with electronic spectral blueshifts. The phenomenon that hydrogen bonds are strengthened in some electronic states while weakened in others can arouse further probe into CH3CO2CH3-(H2O)1, 2 complexes.

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El Hadki, Hamza, Zouhair Lakbaibi, Mohammed Salah, Khadija Marakchi, Oum Keltoum Kabbaj, Maria Luisa Senent et Najia Komiha. « The formation of interstellar organic molecules : H2C3O A DFT and ELF theoretical study ». Mediterranean Journal of Chemistry 9, n^o 3 (28 septembre 2019) : 175–89. http://dx.doi.org/10.13171/mjc93190924420nk.

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This quantum study at B3LYP/6-311 ++ G (d, p) with ELF analysis were performed in order to understand the formation of propynal and cyclopropenone, two molecules detected in the interstellar medium. The formation of these molecules is supposed to be through reactions between carbon monoxide (CO) and acetylene (C2H2) in the cold conditions of interstellar clouds. All the structures, reagents, products and transition states, have been optimized and the geometrical parameters are given as well as the dipole moments. The reaction paths are elaborated and discussed here using the IRC method implemented in the Gaussian program. The determined activation energies allow an estimation of the rate constants. The ELF analysis performed here seems to be a valuable tool for screening the evolution of the bonds during the formation processes. The two reactions probably occur in one step. The propadienone, another possible isomer, has been also studied. It is formed through a third reaction. A stable triplet ground state of this molecule, the thermodynamic consideration and a small dipole moment can explain the fact that it is not detected yet in the interstellar medium. M06-2X and WB97XD functional were also used for comparing results.

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Ивашин, Н. В., et С. Н. Терехов. « Спектры РКР Co(II)- и Cu-5,10,15,20-тетракис[4-(N-метилпиридил)]порфирина в возбужденном dd-состоянии и механизмы его дезактивации в растворе и комплексах с ДНК ». Журнал технической физики 128, n^o 11 (2020) : 1636. http://dx.doi.org/10.21883/os.2020.11.50166.105-20.

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A study of the resonance Raman scattering (RRS) spectra of Co(II)- and Cu-5,10,15,20-tetrakis [4-(N-methylpyridyl)]porphyrin (CoIITMpyP4, CuTMpyP4) in various solvents and in complex with DNA was carried out. Additional lines were found in the RRS spectra of CoIITMpyP4 in a dimethylformamide (DMF) solution containing formic acid as an impurity, as well as for its complex with DNA under nanosecond pulsed excitation. At the same time, under the same excitation conditions, such lines are absent in the spectra of CoIITMpyP4 solutions in pure DMF, dimethyl sulfoxide, water, and alcohols. To interpret the experimental data, we performed calculations of the structure and vibrations for the solvate complexes of CoII - and CuTMpyP4 with water, methanol and formic acid in the ground and in excited states. Based on the data obtained, additional lines in the Raman spectra were assigned to the excited dd-state corresponding to the d(z2) d(x2-y2) transition, the lifetime of which increases with the formation of complexes of CoIITMpyP4 with formic acid. According to the calculation results, this correlates with a decrease in the rate constant of the internal conversion kic due to an increase in the energy gap E between the ground and dd states of CoIITMpyP4. In the case of CoII and CuTMpyP4 binding to DNA, the decrease in kic is due to the additional interaction of the extra-liganding water molecule directly or with the participation of several immobilized DNA water molecules with one of its bases. This complicates the conformational rearrangement of the water molecule in the dd-state, which contributes to an increase in E.

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Sickafoose, S. M., M. D. Morse et D. A. Hales. « The near infrared 2Π3/2(aβJ) ¬ X 2Σ+(bβS) band systems of TiCo and ZrCo ». Canadian Journal of Physics 79, n^o 2-3 (1 février 2001) : 229–45. http://dx.doi.org/10.1139/p01-014.

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Resonant two-photon ionization spectroscopy has been used to provide the first rotationally resolved work involving multiply-bonded mixed earlylate transition metal dimers. The mixed metal dimers TiCo and ZrCo are shown to possess 2Σ+ ground states, in agreement with a previous matrix isolation ESR (electron spin resonance) study on TiCo. Two previously observed vibronic bands in ZrCo are rotationally resolved, as is one of several newly discovered vibronic transitions in TiCo. Ground-state rotational constants for 48Ti59Co and 90Zr59Co are measured to be B''0 = 0.186 15(8) cm1 and B''0 = 0.119 78(5) cm1, giving r''0 = 1.8508(4) and r''0 = 1.9883(4) Å, respectively. In both molecules the ground state conforms to the Hund's case (bβ S) coupling scheme, with Fermi contact interactions between the unpaired σ electron and the 59Co (I = 7/2) nucleus of b''F = 0.0468(7) cm1 for 48Ti59Co and b''F = 0.0549(6) cm1 for 90Zr59Co. These values indicate that the unpaired electron occupies a σ orbital having 32% and 37% Co 4s character in TiCo and ZrCo, respectively. All three of the rotationally resolved bands are 2Π3/2 ¬ X2Σ+ transitions. For 90Zr59Co the 0 ¬ 0 and 1 ¬ 0 bands were resolved at ν0 = 10 496.1452(28) and 10 884.3794(25) cm1, giving B'0 = 0.119 82(6) and B'1 = 0.121 44(5) cm1. For 48Ti59Co the rotationally resolved band has ν0 = 9873.8342(19) cm1 and B' = 0.191 07(6) cm1. These results are discussed in the context of prior work on these and related molecules. PACS No.: 33.20Eq

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Larionova, Joulia, Mathias Gross, Melanie Pilkington, Hanspeter Andres, Helen Stoeckli-Evans, Hans U. Güdel et Silvio Decurtins. « High-Spin Molecules : A Novel Cyano-Bridged MnMo Molecular Cluster with aS=51/2 Ground State and Ferromagnetic Intercluster Ordering at Low Temperatures ». Angewandte Chemie International Edition 39, n^o 9 (2 mai 2000) : 1605–9. http://dx.doi.org/10.1002/(sici)1521-3773(20000502)39:9<1605 ::aid-anie1605>3.0.co;2-5.

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March, N. H. « Differential equations for ground-state electron density and Slater sum in atoms and molecules with and without external fields ». International Journal of Quantum Chemistry 70, n^o 4-5 (1998) : 779–88. http://dx.doi.org/10.1002/(sici)1097-461x(1998)70:4/5<779 ::aid-qua24>3.0.co;2-w.

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Kato, Ryo, Kazuo Hoshino, Haruhisa Nakano, Takanori Shibata, Kenji Miyamoto, Kengo Iwanaka, Katsuya Hayashi et Akiyoshi Hatayama. « Numerical analysis of isotope effect in NIFS negative ion source ». Journal of Physics : Conference Series 2244, n^o 1 (1 avril 2022) : 012035. http://dx.doi.org/10.1088/1742-6596/2244/1/012035.

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Abstract Result of hydrogen (H) and deuterium (D) experiments done by NIFS research and development negative ion source (RNIS) demonstrated that the co-extracted electron current with the negative ions and the electron density in the driver region in the D experiment have been around three times higher than that in the H experiment. To investigate mechanism of this difference, electron transport simulation using 3D kinetic particle tracking model KEIO-MARC code has been modified and applied to analysis of the isotope effect in the NIFS negative ion source. Simulation result suggests that impacts of isotope effects of sheath potential drop, coulomb collisions, and some reactions of ground state molecules and ions on the electron density is not large to explain the experimental result of the increase in the electron density in the plasma.

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Jacob, Arshia M., Karl M. Menten, Helmut Wiesemeyer, Rolf Güsten, Friedrich Wyrowski et Bernd Klein. « First detection of 13CH in the interstellar medium ». Astronomy & ; Astrophysics 640 (août 2020) : A125. http://dx.doi.org/10.1051/0004-6361/201937385.

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In recent years, a plethora of observations with high spectral resolution of sub-millimetre and far-infrared transitions of methylidene (CH), conducted with Herschel and SOFIA, have demonstrated this radical to be a valuable proxy for molecular hydrogen that can be used for characterising molecular gas within the interstellar medium on a Galactic scale, including the CO-dark component. We report the discovery of the 13CH isotopologue in the interstellar medium using the upGREAT receiver on board SOFIA. We have detected the three hyperfine structure components of the ≈2 THz frequency transition from its X2Π1∕2 ground-state towards the high-mass star-forming regions Sgr B2(M), G34.26+0.15, W49(N), and W51E and determined 13CH column densities. The ubiquity of molecules containing carbon in the interstellar medium has turned the determination of the ratio between the abundances of the two stable isotopes of carbon, 12C/13C, into a cornerstone for Galactic chemical evolution studies. Whilst displaying a rising gradient with galactocentric distance, this ratio, when measured using observations of different molecules (CO, H2CO, and others), shows systematic variations depending on the tracer used. These observed inconsistencies may arise from optical depth effects, chemical fractionation, or isotope-selective photo-dissociation. Formed from C+ either through UV-driven or turbulence-driven chemistry, CH reflects the fractionation of C+, and does not show any significant fractionation effects, unlike other molecules that were previously used to determine the 12C/13C isotopic ratio. This makes it an ideal tracer for the 12C/13C ratio throughout the Galaxy. By comparing the derived column densities of 13CH with previously obtained SOFIA data of the corresponding transitions of the main isotopologue 12CH, we therefore derive 12C/13C isotopic ratios toward Sgr B2(M), G34.26+0.15, W49(N) and W51E. Adding our values derived from 12∕13CH to previous calculations of the Galactic isotopic gradient, we derive a revised value of 12C/13C = 5.87(0.45)RGC + 13.25(2.94).

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Nakamura, Masaaki, Po-Yu Tsai, Toshio Kasai, King-Chuen Lin, Federico Palazzetti, Andrea Lombardi et Vincenzo Aquilanti. « Dynamical, spectroscopic and computational imaging of bond breaking in photodissociation : roaming and role of conical intersections ». Faraday Discussions 177 (2015) : 77–98. http://dx.doi.org/10.1039/c4fd00174e.

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Recent experimental and theoretical advances in the study of the dissociation of excited molecules are revealing unexpected mechanisms, when their outcomes are tackled by combining (i) space-time ion imaging of translational features, with (ii) spectroscopic probing of rotational and vibrational distributions; crucial is the assistance of (iii) the quantum chemistry of structural investigations of rearrangements of chemical bonds, and of (iv) the simulations of molecular dynamics to follow the evolution of selective bond stretching and breaking. Here we present results of such an integrated approach to methyl formate, HCOOCH₃, the simplest of esters; the main focus is on the rotovibrationally excited CO (v = 1) product and in general on the energy distribution in the fragments. Previous laser studies of dissociation into CO and CH₃OH at a sequence of various wavelengths discovered signatures of a roaming mechanism by the late arrival of CO (v = 0) products in time-of-flight ion imaging. Subsequent detailed investigations as a function of excitation energy provided the assessment of the threshold, which opens for triple breakdown into CO and further fragments H and CH₃O, as spectroscopically characterized by ion imaging and FTIR respectively. Accompanying quantum mechanical electronic structure calculations and classical molecular dynamics simulations clarify the origin of these fragments through “roaming” pathways involving incipient radical intermediates at energies below the triple fragmentation threshold: a specific role is played by nonadiabatic transitions at a conical intersection between ground and excited states; alternative pathways focalize our attention to regions of the potential energy surfaces other than those in the neighbourhoods of saddle points along minimum energy paths: eventually this leads us to look for avenues in reaction kinetics beyond those of venerable transition state theories.

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RICHTER-ADDO, GEORGE B. « Interactions of nitric oxide and organic nitroso compounds with metalloporphyrins and heme ». Journal of Porphyrins and Phthalocyanines 04, n^o 04 (juin 2000) : 354–57. http://dx.doi.org/10.1002/(sici)1099-1409(200006/07)4:4<354 ::aid-jpp240>3.0.co;2-v.

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The chemistry of nitric oxide (NO) has taken on new dimensions since the discovery, about a decade ago, of a myriad of biological events that NO participates in. Many of the foundations of metal-NO chemistry were laid out earlier by inorganic chemists and biochemists investigating the structures and electronic properties of the heme-NO moiety or its model compounds. Certainly, the persistent work over the last three decades by chemists working with metal nitrosyls has paid off. Current areas of research in heme-NO chemistry include (i) how the NO group approaches and binds to the metal center (or how it dissociates from the metal center); (ii) the ground state and excited state geometries of the metal-NOfragment; (iii) effects of the trans axial ligands on NO orientation and/or dissociation; and (iv) N-N bond formation from NO molecules catalyzed by heme groups.

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Da Silva, Clarissa O., F�bio Eduardo C. Teixeira, Jos� Andr� T. Azevedo, Edilson C. Da Silva et Marco Antonio Chaer Nascimento. « Theoretical characterization of the ground state of the alkaline-earth monocarbides : Ordering of the two lower-lying states of the BeC, MgC, and CaC molecules ». International Journal of Quantum Chemistry 60, n^o 1 (5 octobre 1996) : 433–38. http://dx.doi.org/10.1002/(sici)1097-461x(1996)60:1<433 ::aid-qua42>3.0.co;2-a.

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Lu, Qiuchen, Ming Qiu, Meiyu Zhao, Zhuo Li et Yuanzuo Li. « Modification of NFA-Conjugated Bridges with Symmetric Structures for High-Efficiency Non-Fullerene PSCs ». Polymers 11, n^o 6 (2 juin 2019) : 958. http://dx.doi.org/10.3390/polym11060958.

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As electron acceptors, non-fullerene molecules can overcome the shortcomings of fullerenes and their derivatives (such as high cost, poor co-solubility, and weak light absorption). The photoelectric properties of two potential non-fullerene polymer solar cells (PSCs) PBDB-T:IF-TN (PB:IF) and PBDB-T:IDT-TN (PB:IDT) are studied by density functional theory (DFT) and time-dependent DFT (TD-DFT). Based on the optimized structure of the ground state, the effects of the electron donor (D) and electron acceptor (A) (D/A) interfaces PBDB-T/IF-TN (PB/IF) and PBDB-T/IDT-TN (PB/IDT) are studied by a quantum-chemical method (QM) and Marcus theory. Firstly, for two non-fullerene acceptors (NFAs) IF-TN and IDT-TN, the NFA IDT-TN has better optical absorption ability and better electron transport ability than IF-TN. Secondly, for the D/A interfaces PB/IF and PB/IDT, they both have high optical absorption and electron transfer abilities, and PB/IDT has better optical absorption and lower exciton binding energy. Finally, some important parameters (open-circuit voltage, voltage loss, fill factor, and power conversion efficiency) are calculated and simulated by establishing the theoretical model. From the above analysis, the results show that the non-fullerene PSC PB:IDT has better photoelectric characteristics than PB:IF.

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Chuang, K. J., G. Fedoseev, D. Qasim, S. Ioppolo, C. Jäger, Th Henning, M. E. Palumbo, E. F. van Dishoeck et H. Linnartz. « Formation of complex molecules in translucent clouds : acetaldehyde, vinyl alcohol, ketene, and ethanol via “nonenergetic” processing of C2H2 ice ». Astronomy & ; Astrophysics 635 (mars 2020) : A199. http://dx.doi.org/10.1051/0004-6361/201937302.

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Context. Complex organic molecules (COMs) have been identified toward high- and low-mass protostars as well as molecular clouds, suggesting that these interstellar species originate from the early stage(s) of starformation. The reaction pathways resulting in COMs described by the formula C2HnO, such as acetaldehyde (CH3CHO), vinyl alcohol (CH2CHOH), ketene (CH2CO), and ethanol (CH3CH2OH), are still under debate. Several of these species have been detected in both translucent and dense clouds, where chemical processes are dominated by (ground-state) atom and radical surface reactions. Therefore, efficient formation pathways are needed to account for their appearance well before the so-called catastrophic CO freeze-out stage starts. Aims. In this work, we investigate the laboratory possible solid-state reactions that involve simple hydrocarbons and OH-radicals along with H2O ice under translucent cloud conditions (1 ≤ AV ≤ 5 and nH ~ 103 cm−3). We focus on the interactions of C2H2 with H-atoms and OH-radicals, which are produced along the H2O formation sequence on grain surfaces at 10 K. Methods. Ultra-high vacuum experiments were performed to study the surface chemistry observed during C2H2 + O2 + H codeposition, where O2 was used for the in situ generation of OH-radicals. These C2H2 experiments were extended by a set of similar experiments involving acetaldehyde (CH3CHO) – an abundant product of C2H2 + O2 + H codeposition. Reflection absorption infrared spectroscopy was applied to in situ monitor the initial and newly formed species. After that, a temperature-programmed desorption experiment combined with a quadrupole mass spectrometer was used as a complementary analytical tool. The IR and QMS spectral assignments were further confirmed in isotope labeling experiments using 18O2. Results. The investigated 10 K surface chemistry of C2H2 with H-atoms and OH-radicals not only results in semi and fully saturated hydrocarbons, such as ethylene (C2H4) and ethane (C2H6), but it also leads to the formation of COMs, such as vinyl alcohol, acetaldehyde, ketene, ethanol, and possibly acetic acid. It is concluded that OH-radical addition reactions to C2H2, acting as a molecular backbone, followed by isomerization (i.e., keto-enol tautomerization) via an intermolecular pathway and successive hydrogenation provides so far an experimentally unreported solid-state route for the formation of these species without the need of energetic input. The kinetics of acetaldehyde reacting with impacting H-atoms leading to ketene and ethanol is found to have a preference for the saturated product. The astronomical relevance of the reaction network introduced here is discussed.

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Saberi, M., H. Olofsson, W. H. T. Vlemmings, E. De Beck, T. Khouri et S. Ramstedt. « CO and HCN isotopologue ratios in the outflows of AGB stars ». Astronomy & ; Astrophysics 638 (juin 2020) : A99. http://dx.doi.org/10.1051/0004-6361/202037668.

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Context. Isotopologue line intensity ratios of circumstellar molecules have been widely used to trace the photospheric elemental isotopic ratios of evolved stars. However, depending on the molecular species and the physical conditions of the environment, the isotopologue ratio in the circumstellar envelope (CSE) may deviate considerably from the stellar atmospheric value. Aims. In this paper, we aim to examine how the 12CO/13CO and H12CN/H13CN abundance ratios vary radially due to chemical reactions in the outflows of asymptotic giant branch (AGB) stars and the effect of excitation and optical depth on the resulting line intensity ratios. We study both carbon-rich (C-type) and oxygen-rich (O-type) CSEs. Methods. We performed chemical modeling to derive radial abundance distributions of our selected species in the CSEs over a wide range of mass-loss rates (10−8 < Ṁ < 10−4 M⊙ yr−1). We used these as input in a non-local thermodynamic equilibrium radiative transfer code to derive the line intensities of several ground-state rotational transitions. We also test the influence of stellar parameters, physical conditions in the outflows, the intensity of the interstellar radiation field, and the importance of considering the chemical networks in our model results. Results. We quantified deviations from the atmospheric value for typical outflows. We find that the circumstellar value of 12CO/13CO can deviate from its atmospheric value by up to 25–94% and 6–60% for C- and O-type CSEs, respectively, in radial ranges that depend on the mass-loss rate. We show that variations of the intensity of the interstellar radiation field and the gas kinetic temperature can significantly influence the CO isotopologue abundance ratio in the outer CSEs of both C-type and O-type. On the contrary, the H12CN/H13CN abundance ratio is stable throughout the CSEs for all tested mass-loss rates. The radiative transfer modeling shows that the integrated line intensity ratio I12CO/I13CO of different rotational transitions varies significantly for stars with mass-loss rates in the range from 10−7 to 10−6 M⊙ yr−1 due to combined chemical and excitation effects. In contrast, the excitation conditions for the HCN isotopologues are the same for both isotopologues. Conclusions. We demonstrate the importance of using the isotopologue abundance profiles from detailed chemical models as inputs to radiative transfer models in the interpretation of isotopologue observations. Previous studies of circumstellar CO isotopologue ratios are based on multi-transition data for individual sources and it is difficult to estimate the errors in the reported values due to assumptions that are not entirely correct according to this study. If anything, previous studies may have overestimated the circumstellar 12CO/13CO abundance ratio. The use of the HCN molecule as a tracer of C isotope ratios is affected by fewer complicating problems, but we note that the corrections for high optical depths are very large in the case of high-mass-loss-rate C-type CSEs; and in O-type CSEs the H13CN lines may be too weak to detect.

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Ramirez, Rafael, et Michael C. Böhm. « Band Structures of Intercalation Compounds. The System (NH4)(NH3)3(TiS2)4 ». Zeitschrift für Naturforschung A 42, n^o 11 (1 novembre 1987) : 1346–56. http://dx.doi.org/10.1515/zna-1987-1119.

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The electronic band structure of the intercalation system ammonia TiS2 has been investigated by a semiempirical self-consistent-field (SCF) Hartree-Fock (HF) crystal orbital (CO) formalism supplemented by an INDO (intermediate neglect of differential overlap) Hamiltonian. A two-dimensional (2D) model for the title system with stoichiometry (NH4)(NH3)3(TiS2)4 has been selected on the basis of available experimental data. The model is defined via a TiS2 monolayer coupled to the intercalant monolayer. The corresponding band-structure properties are compared with bandstructure calculations of monolayered TiS2 and bulk TiS2 . For TiS2 available experimental data and numerical results of conventional band-structure approaches are reported. The interaction between the guest-molecules and the host lattice has the character of a redox-process; i.e. one electron per formula unit has been transferred from the intercalant to the TiS2 layer. One consequence of this transfer is a semiconductor-to-metal transition upon intercalation; an additional consequence is a remarkable electronic reorganization in the TiS2 host. The surplus of electronic charge is predominantly localized at the S centers. The electronic states at the Fermi-level are of Ti 3d character. Two electronic configurations of the title system have been investigated. The mean-field ground state is of a charge density wave type with respect to the TiS2 sublattice. A “symmetry adapted” (SA) configuration is predicted at higher energy.

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Zapunidy, Sergey A., Dmitry S. Martyanov, Elena M. Nechvolodova, Marina V. Tsikalova, Yuri N. Novikov et Dmitry Yu Paraschuk. « Approaches to low-bandgap polymer solar cells : Using polymer charge-transfer complexes and fullerene metallocomplexes ». Pure and Applied Chemistry 80, n^o 10 (1 janvier 2008) : 2151–61. http://dx.doi.org/10.1351/pac200880102151.

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Polymer solar cells have shown high potential to convert solar energy into electricity in a cost-effective way. One of the basic reasons limiting the polymer solar cell efficiency is insufficient absorption of the solar radiation by the active layer that limits the photocurrent. To increase the photocurrent, one needs low-bandgap materials with strong absorption below 2 eV. In this work, we study two types of low-bandgap materials: ground-state charge-transfer complexes (CTCs) of a conjugated polymer, MEH-PPV (poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene]), and an exohedral metallocomplex of fullerene, (η2-C60)IrH(CO)[(+)DIOP] (IrC60). We demonstrate that the CTC formed between MEH-PPV and conjugated molecules with high electron affinity, namely, 2,4,7-trinitrofluorenone (TNF) and 1,5-dinitroantraquinone (DNAQ), can have strong optical absorption extending down to the near infrared. We have observed that the photoexcited CTC can generate free charges. We also report on optical studies of IrC60 as a possible acceptor for polymer/fullerene solar cells. IrC60 strongly absorbs in the visible spectral range, in particular in the red part, and therefore has a potential for increasing the photocurrent as compared with polymer/methanofullerene solar cells. Our studies of MEH-PPV/IrC60 blended films show that long-lived charges are efficiently generated at MEH-PPV upon photoexcitation of the blend.

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Sakiyama, Hiroshi, Yuya Yamamoto, Ryusei Hoshikawa et Ryoji Mitsuhashi. « Crystal Structures and Magnetic Properties of Diaquatetrapyridinenickel(II) and Diaquatetrapyridinecobalt(II) Complexes ». Magnetochemistry 9, n^o 1 (30 décembre 2022) : 14. http://dx.doi.org/10.3390/magnetochemistry9010014.

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Metal complexes with pyridine ligands (py) have not been crystallographically characterized in large numbers, while a large number of 2,2′-bipyridine (bpy) complexes have been structurally characterized. Against this background of scarcity of py complexes, the aim of this study was to characterize the structures and magnetic properties of complexes with pyridine ligands. In this study, new py complexes, trans-[Ni(H2O)2(py)4][BPh4]2·4py (1) and trans-[Co(H2O)2(py)4][BPh4]2·4py (2), were prepared and characterized by the single-crystal X-ray diffraction method and magnetic measurements. In the crystal structure analysis, both complexes were found to have octahedral trans-N2O4 coordination geometry, and the coordination of the trans-aqua ligands was found to be enhanced by the hydrogen-bonded pyridine molecules as a base. In the simultaneous analysis of magnetic susceptibility and magnetization, both complexes were found to show strong magnetism in one direction (χz > χx, χy; Mz > Mx, My), and this was explained by the enhancement of the axial aqua ligands. In the nickel(II) complex, the strong axial ligand field was found to cause negative zero-field splitting (D < 0) to show the magnetic behavior, while in the cobalt(II) complex, the strong axial π-orbital effect was found to cause negative ligand field splitting (Δ) in the 4T1 ground state to show the magnetic behavior.

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Giannetti, A., S. Bovino, P. Caselli, S. Leurini, D. R. G. Schleicher, B. Körtgen, K. M. Menten, T. Pillai et F. Wyrowski. « A timeline for massive star-forming regions via combined observation of o-H2D+ and N2D+ ». Astronomy & ; Astrophysics 621 (janvier 2019) : L7. http://dx.doi.org/10.1051/0004-6361/201834602.

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Context. In cold and dense gas prior to the formation of young stellar objects, heavy molecular species (including CO) are accreted onto dust grains. Under these conditions H3+ and its deuterated isotopologues become more abundant, enhancing the deuterium fraction of molecules such as N2H+ that are formed via ion-neutral reactions. Because this process is extremely temperature sensitive, the abundance of these species is likely linked to the evolutionary stage of the source. Aims. We investigate how the abundances of o-H2D+ and N2D+ vary with evolution in high-mass clumps. Methods. We observed with APEX the ground-state transitions of o-H2D+ near 372 GHz, and N2D+(3–2) near 231 GHz for three massive clumps in different evolutionary stages. The sources were selected within the G351.77–0.51 complex to minimise the variation of initial chemical conditions, and to remove distance effects. We modelled their dust continuum emission to estimate their physical properties, and also modelled their spectra under the assumption of local thermodynamic equilibrium to calculate beam-averaged abundances. Results. We find an anticorrelation between the abundance of o-H2D+ and that of N2D+, with the former decreasing and the latter increasing with evolution. With the new observations we are also able to provide a qualitative upper limit to the age of the youngest clump of about 105 yr, comparable to its current free-fall time. Conclusions. We can explain the evolution of the two tracers with simple considerations on the chemical formation paths, depletion of heavy elements, and evaporation from the grains. We therefore propose that the joint observation and the relative abundance of o-H2D+ and N2D+ can act as an efficient tracer of the evolutionary stages of the star-formation process.

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Witt, A. N. « Blue Luminescence and Extended Red Emission : Possible Connections to the Diffuse Interstellar Bands ». Proceedings of the International Astronomical Union 9, S297 (mai 2013) : 173–79. http://dx.doi.org/10.1017/s1743921313015810.

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AbstractBlue luminescence (BL) and extended red emission (ERE) are observed as diffuse, optical-wavelength emissions in interstellar space, resulting from photoluminescence by ultraviolet(UV)-illuminated interstellar grains. Faintness and the challenge of separating the BL and ERE from the frequently much brighter dust-scattered continuum present major observational hurdles, which have permitted only slow progress in testing the numerous models that have been advanced to explain these two phenomena. Both the ERE, peaking near 680 nm (FWHM ~ 60 - 120 nm) and the BL, asymmetrically peaking at ~ 378 nm (FWHM ~ 45 nm), were first discovered in the Red Rectangle nebula. Subsequently, ERE and BL have been observed in other reflection nebulae, and in the case of the ERE, in carbon-rich planetary nebulae, H II regions, high-latitude cirrus clouds, the galactic diffuse ISM, and in external galaxies. BL exhibits a close spatial and intensity correlation with emission in the aromatic emission feature at 3.3 micron, most likely arising from small, neutral polycyclic aromatic hydrocarbon (PAH) molecules. The spectral characteristics of the BL also agree with those of fluorescence by PAH molecules with 13 to 19 carbon atoms. The BL phenomenon is thus most readily understood as the optical fluorescence of small, UV-excited aromatic molecules. The ERE, by contrast, though co-existent with mid-IR PAH emissions, does not correlate with emissions from either neutral or ionized PAHs. Instead, the spatial ERE morphology appears to be strictly governed by the density of far-UV (E ≥ 10.5 eV) photons, which are required for the ERE excitation. The most restrictive observational constraint for the ERE process is its exceptionally high quantum efficiency. If the ERE results from photo-excitation of a nano-particle carrier by photons with E ≥ 10.5 eV in a single-step process, the quantum efficiency exceeds 100%. Such a process, in which one to three low-energy optical photons may be emitted following a single far-UV excitation, is possible in highly isolated small clusters, e.g. small, dehydrogenated carbon clusters with about 20 to 28 carbon atoms. A possible connection between the ERE carriers and the carriers of DIBs may exist in that both are ubiquitous throughout the diffuse interstellar medium and both have an abundance of low-lying electronic levels with E ≤ 2.3 eV above the ground state.

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Le Floch, André. « Revised molecular constants for the ground state of CO ». Molecular Physics 72, n^o 1 (janvier 1991) : 133–44. http://dx.doi.org/10.1080/00268979100100081.

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Garcia-Bach, M. A., D. J. Klein et R. Valenti. « TRANSFER-MATRIX METHOD FOR SOLVING THE SPIN 1/2 ANTIFERROMAGNETIC HEISENBERG CHAIN ». International Journal of Modern Physics B 02, n^o 05 (octobre 1988) : 1035–36. http://dx.doi.org/10.1142/s021797928800086x.

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Following the discovery of high Tc superconductivity in the copper oxides, there has been a great deal of interest in the RVB wave function proposed by Anderson [1]. As a warm-up exercise we have considered a valence-bond wave function for the one dimensional spin-1/2 Heisenberg chain. The main virtue of our work is to propose a new variational singlet wavefunction which is almost analytically tractable by a transfer-matrix technique. We have obtained the ground state energy for finite as well as infinite chains, in good agreement with exact results. Correlation functions, excited states, and the effects of other interactions (e.g., spin-Peierls) are also accessible within this scheme [2]. Since the ground state of the chain is known to be a singlet (Lieb & Mattis [3]), we write the appropriate wave function as a superposition of valence-bond singlets, [Formula: see text], where | k > is a spin configuration obtained by pairing all spins into singlet pairs, in a way which is common in valence-bond calculations of large molecules. As in that case, each configuration, | k >, can be represented by a Rümer diagram, with directed bonds connecting each pair of spins on the chain. The c k 's are variational co-efficients, the form of which is determined as follows: Each singlet configuration (Rümer diagram) is divided into "zones", a "zone" corresponding to the region between two consecutive sites. Each zone is indexed by its distance from the end of the chain and by the number of bonds crossing it. Our procedure assigns a variational parameter, x ij , to the j th zone, when crossed by i bonds. The resulting wavefunction for an N-site chain is written as [Formula: see text] where m ij(k) equals 1 when zone j is crossed by i bonds and zero otherwise. To make the calculation tractable we reduce the number of variational parameters by disallowing configurations with bonds connecting any two sites separated by more than 2M lattice points. (For simplicity, we have limited ourselves to M=3, but the scheme can be used for any M). With the simple ansatz, matrix elements can be calculated by a transfer-matrix method. To understand the transfer-matrix method note that since only local zone parameters appear in the description of each state | k >, matrix elements and overlaps, [Formula: see text] and < k | k '>, are completely specified by a small number of "local states" associated with each zone. Within a given zone a local state is defined by (i) the number of bonds crossing the zone and (ii), by whether the bonds originate from the initial (| k >) or final (| k '>) state. It is then easy to see that "local states" of consecutive zones are connected by a 15 × 15 transfer matrix (for the case M=3). Furthermore, the overlap matrix element can be written as a product of transfer-matrices associated with each zone of the chain. When calculating matrix elements of the Hamiltonian, an additional matrix, U , must be defined, to represent the particular zone involving the two spins connected by the Heisenberg interaction. The relevant details as well as the comparison with exact results will be given elsewhere. We are planning to ultimately apply this method to the two dimensional case, and hope to include the effects of holes.

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Jacob, Arshia M., Karl M. Menten, Helmut Wiesemeyer, Min-Young Lee, Rolf Güsten et Carlos A. Durán. « Fingerprinting the effects of hyperfine structure on CH and OH far infrared spectra using Wiener filter deconvolution ». Astronomy & ; Astrophysics 632 (28 novembre 2019) : A60. http://dx.doi.org/10.1051/0004-6361/201936037.

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Context. Despite being a commonly observed feature, the modification of the velocity structure in spectral line profiles by hyperfine structure complicates the interpretation of spectroscopic data. This is particularly true for observations of simple molecules such as CH and OH toward the inner Galaxy, which show a great deal of velocity crowding. Aims. In this paper, we investigate the influence of hyperfine splitting on complex spectral lines, with the aim of evaluating canonical abundances by decomposing their dependence on hyperfine structures. This is achieved from first principles through deconvolution. Methods. We present high spectral resolution observations of the rotational ground state transitions of CH near 2 THz seen in absorption toward the strong FIR-continuum sources AGAL010.62 − 00.384, AGAL034.258+00.154, AGAL327.293 − 00.579, AGAL330.954 − 00.182, AGAL332.826 − 00.549, AGAL351.581 − 00.352 and SgrB2(M). These were observed with the GREAT instrument on board SOFIA. The observed line profiles of CH were deconvolved from the imprint left by the lines’ hyperfine structures using the Wiener filter deconvolution, an optimised kernel acting on direct deconvolution. Results. The quantitative analysis of the deconvolved spectra first entails the computation of CH column densities. Reliable N(CH) values are of importance owing to the status of CH as a powerful tracer for H2 in the diffuse regions of the interstellar medium. The N(OH)/N(CH) column density ratio is found to vary within an order of magnitude with values ranging from one to 10, for the individual sources that are located outside the Galactic centre. Using CH as a surrogate for H2, we determined the abundance of the OH molecule to be X(OH) = 1.09 × 10−7 with respect to H2. The radial distribution of CH column densities along the sightlines probed in this study, excluding SgrB2(M), showcase a dual peaked distribution peaking between 5 and 7 kpc. The similarity between the correspondingly derived column density profile of H2 with that of the CO-dark H2 gas traced by the cold neutral medium component of [CII] 158 μm emission across the Galactic plane, further emphasises the use of CH as a tracer for H2.

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Sandqvist, Aa, Å. Hjalmarson, B. Larsson, U. Frisk, S. Lundin et G. Rydbeck. « Herschel and Odin observations of H2O, CO, CH, CH+, and [N II] in the barred spiral galaxy NGC 1365 ». Astronomy & ; Astrophysics 647 (mars 2021) : A86. http://dx.doi.org/10.1051/0004-6361/202038875.

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Context. The Odin satellite is now into its twentieth year of operation, much surpassing its design life of two years. One of its major astronomical pursuits was the search for and study of water vapor in diverse regions of the Solar System and the Milky Way galaxy. The Herschel space observatory was needed to detect water vapor in external galaxies. Aims. Our goal is to study the distribution and excitation of water vapor and other molecules in the barred spiral galaxy NGC 1365. Methods. Herschel has observed the central region of NGC 1365 in two positions, and both its SPIRE and PACS observations are available in the Herschel Science Archive. Herschel PACS images have been produced of the 70 and 160 μm infrared emission from the whole galaxy, and also of the cold dust distribution as obtained from the ratio of the 160 to 70 μm images. The Herschel SPIRE observations have been used to produce simultaneously observed maps of the 557 GHz o-H2O, 752 GHz p-H2O, 691 GHz CO(6−5), 1037 GHz CO(9−8), 537 GHz CH, 835 GHz CH+, and the 1461 GHz [N II] lines (efficiently probing the warm ionized medium) in the inner bar and circumnuclear torus region; – however, these observations have no effective velocity resolution. For this reason Odin has recently observed the 557 GHz ortho-H2O ground state line in the central region with high (5 km s−1) spectral resolution. Results. The emission and absorption of H2O at 557 GHz, with a velocity resolution of 5 km s−1, has been marginally detected in NGC 1365 with Odin. The water vapor is predominantly located in a shocked 15″ (1.3 kpc) region near some central compact radio sources and hot-spot H II regions, close to the northeast component of the molecular torus surrounding the nucleus. An analysis of the H2O line intensities and velocities indicates that a shock-region is located here. This is corroborated by a statistical image deconvolution of our SEST CO(3−2) observations, yielding 5″ resolution, and a study of our Very Large Array H I absorption observations, as well as comparisons with published interferometric CO observations. Additionally, an enticing 20″ H I ridge is found to extend south-southeast from the nucleus, coinciding in position with the southern edge of an O III outflow cone, emanating from the nucleus. The molecular chemistry of the shocked central region of NGC 1365 is analyzed with special emphasis on the CO, H2O and CH, CH+ results. Conclusions. The dominating activity near the northeast (NE) torus component may have been triggered by the rapid bar-driven inflow into the circumnuclear torus causing cloud-cloud collisions and shocks, leading to the formation of stellar superclusters and, hence, also to more efficient PDR chemistry, which, here, may also benefit from cosmic ray focusing caused by the observed aligned magnetic field. The very high activity near the NE torus component may reflect the fact that the eastern bar-driven gas inflow into the NE region is much more massive than the corresponding western gas inflow into the southwest region. The H2O and CH+ emissions peak in the NE torus region, but the CO and CH emissions are more evenly distributed across the whole circumnuclear torus. The higher energy CO spectral line energy distribution (SLED) is nicely modeled by a low velocity (10 km s−1) shock, which may as well explain the required CH excitation and its high abundance in denser gas. The higher velocity (40 km s−1) shock required to model the H2O SLED in the NE torus region, paired with the intense UV radiation from the observed massive young stellar superclusters, may also explain the high abundance of CH+ in this region. The nuclear H I ridge may have been created by the action of outflow-driving X-ray photons colliding with ice-covered dust grains. A precessing nuclear engine, as is suggested by the tilted massive inner gas torus, may be necessary to explain the various nuclear outflows encountered.

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Hampson, Carl A., James A. Howard et Brynmor Mile. « The e.s.r. spectrum of Ag(CO)3, a 2A1 ? ground state molecule ». Journal of the Chemical Society, Chemical Communications, n^o 14 (1985) : 966. http://dx.doi.org/10.1039/c39850000966.

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Fan Qun-Chao, Sun Wei-Guo, Li Hui-Dong et Feng Hao. « P-branch spectral lines of rovibrational transitions of CO molecule in ground state ». Acta Physica Sinica 60, n^o 6 (2011) : 063301. http://dx.doi.org/10.7498/aps.60.063301.

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Mogensen, D., R. Gierens, J. N. Crowley, P. Keronen, S. Smolander, A. Sogachev, A. C. Nölscher et al. « Simulations of atmospheric OH, O<sub>3</sub> ; and NO<sub>3</sub> ; reactivities within and above the boreal forest ». Atmospheric Chemistry and Physics 15, n^o 7 (15 avril 2015) : 3909–32. http://dx.doi.org/10.5194/acp-15-3909-2015.

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Abstract. Using the 1-D atmospheric chemistry transport model SOSAA, we have investigated the atmospheric reactivity of a boreal forest ecosystem during the HUMPPA-COPEC-10 campaign (summer 2010, at SMEAR~II in southern Finland). For the very first time, we present vertically resolved model simulations of the NO3 and O3 reactivity (R) together with the modelled and measured reactivity of OH. We find that OH is the most reactive oxidant (R ∼ 3 s-1) followed by NO3 (R ∼ 0.07 s-1) and O3 (R ∼ 2 × 10-5s-1). The missing OH reactivity was found to be large in accordance with measurements (∼ 65%) as would be expected from the chemical subset described in the model. The accounted OH radical sinks were inorganic compounds (∼ 41%, mainly due to reaction with CO), emitted monoterpenes (∼ 14%) and oxidised biogenic volatile organic compounds (∼ 44%). The missing reactivity is expected to be due to unknown biogenic volatile organic compounds and their photoproducts, indicating that the true main sink of OH is not expected to be inorganic compounds. The NO3 radical was found to react mainly with primary emitted monoterpenes (∼ 60%) and inorganic compounds (∼ 37%, including NO2). NO2 is, however, only a temporary sink of NO3 under the conditions of the campaign (with typical temperatures of 20–25 °C) and does not affect the NO3 concentration. We discuss the difference between instantaneous and steady-state reactivity and present the first boreal forest steady-state lifetime of NO3 (113 s). O3 almost exclusively reacts with inorganic compounds (∼ 91%, mainly NO, but also NO2 during night) and less with primary emitted sesquiterpenes (∼ 6%) and monoterpenes (∼ 3%). When considering the concentration of the oxidants investigated, we find that OH is the oxidant that is capable of removing organic compounds at a faster rate during daytime, whereas NO3 can remove organic molecules at a faster rate during night-time. O3 competes with OH and NO3 during a short period of time in the early morning (around 5 a.m. local time) and in the evening (around 7–8 p.m.). As part of this study, we developed a simple empirical parameterisation for conversion of measured spectral irradiance into actinic flux. Further, the meteorological conditions were evaluated using radiosonde observations and ground-based measurements. The overall vertical structure of the boundary layer is discussed, together with validation of the surface energy balance and turbulent fluxes. The sensible heat and momentum fluxes above the canopy were on average overestimated, while the latent heat flux was underestimated.

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LIU, JUN, SHENG-BIAO TAN et HUI-NING DONG. « STABLE STRUCTURES, ELECTRIC AND MAGNETIC PROPERTIES OF NANOPARTICLES COn(n = 1-6) CLUSTERS : FIRST-PRINCIPLES CALCULATIONS ». International Journal of Modern Physics B 27, n^o 15 (4 juin 2013) : 1362007. http://dx.doi.org/10.1142/s0217979213620075.

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The ground state geometric structures of the nanoparticles or clusters CO n(n = 1-6) were given based on the first-principles calculations. Then the magnetic properties of the clusters CO n(n = 1-6) and ( CO n)-2(n = 1-6) were calculated in system. Results show that their ground state structures are closely related to the numbers of O-ions. These clusters have no magnetic moments and half-metallicity if they are electroneutral. However, they have magnetic moments if they have positive or negative charges. The total magnetic moments of the clusters ( CO n)-2(n = 1-6, but n≠3) are all 2.0000 μB, and all their ions have contributions to the total magnetic moments. The main reason is that the molecular orbitals with lower energy filled with paired electrons and the molecular orbitals with higher energy are occupied by two electrons in parallel.

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Klein, Hans-Friedrich, Michael Helwig, Udo Koch, Goetz Lull, Marko Tadic, Carl Krüger et Peter Hofmann. « Diolefinbis(trimethyIphosphine)cobalt(0) Compounds : Stable Organometallic Radicals with Distorted Ground State Structures ». Zeitschrift für Naturforschung B 43, n^o 11 (1 novembre 1988) : 1427–38. http://dx.doi.org/10.1515/znb-1988-1107.

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Abstract Diolefincobalt(O) complexes Co(L2)(PMe3)2 {L2 -[CH2 = CHSi(OMe)2]2O (1), [CH2 =CHSi(OEt)2]2O (2), (CH2 =CHCH2)2SiMe2 (3), [(CH2 =CHCH2)2N]2CH2 (4)} have been synthesized from Co(C5H8)(PMe3)3 and diolefins at ambient temperatures. Reactions with allyl ethers or with allyltin or allylphosphorus compounds involve transfer of allyl groups to the cobalt, while allylamine simply replaces cyclopentene (C5H8) to give Co(CH2 =CHCH2NH2)(PMe3)3 (5). Cationic cobalt(I) complexes containing olefin ligands as in 1-4 could not be obtained under conditions where norbornadiene readily gave [Co(C7H8)(PMe3)3 ]BF4 (6). Paramagnetic 4 shows a magnetic moment μeff = 2.0 μв (between 3.6 and 293 K), corresponding to one unpaired electron per cobalt atom. Compound 4 crystallizes in the space group P21/c with Z = 4, a = 14.986(4), b = 17.223(5), c = 15.436(3) Å,β = 117.98(2)°, V = 3518.4 Å3 . Each cobalt atom is η4-coordinated to a diolefin involving the smaller of two possible chelating rings. The Co-C distances range only from 2.029(6) to 2.058(6) Å for the olefin ligands, whereas Co-P bond lengths at each cobalt differ significantly: Co1-P1 2.188(2), Co1-P2 2.248(2); Co2-P3 2.185(2), Co2-P4 2.258(2) Å. This feature of two significantly different Co-L bond lengths is hitherto seen in all structurally characterized (bisolefin)CoL2 complexes (L = PMe3, CH3CN) and can be rationalized by molecular orbital calculations (Extended Hückel) on the 17 electron model system (PH3)2Co(C2H4)2.

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Nasehnia, F., et M. Seifi. « Adsorption of molecular oxygen on VIIIB transition metal-doped graphene : A DFT study ». Modern Physics Letters B 28, n^o 30 (10 décembre 2014) : 1450237. http://dx.doi.org/10.1142/s0217984914502376.

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Adsorption of molecular oxygen with a triplet ground state on Fe -, Co -, Ni -, Ru -, Rh -, Pd -, OS -, Ir - and Pt -doped graphene is studied using density functional theory (DFT) calculations. The calculations show that O 2 molecule is chemisorbed on the doped graphene sheets with large adsorption energies ranging from -0.653 eV to -1.851 eV and the adsorption process is irreversible. Mulliken atomic charge analysis of the structure shows that charge transfer from doped graphene sheets to O 2 molecule. The amounts of transferred charge are between 0.375e- to 0.650e-, indicating a considerable change in the structures conductance. These results imply that the effect of O 2 adsorption on transition metal-doped graphene structures can alter the possibility of using these materials as a toxic-gas (carbon monoxide, hydrogen fluoride, etc.) sensor.

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Bao, Xiaoguang, Xin Zhou, Charity Flener Lovitt, Amruth Venkatraman, David A. Hrovat, Rolf Gleiter, Roald Hoffmann et Weston Thatcher Borden. « Molecular Orbitals of the Oxocarbons (CO)n, n = 2–6. Why Does (CO)4 Have a Triplet Ground State ? » Journal of the American Chemical Society 134, n^o 24 (11 juin 2012) : 10259–70. http://dx.doi.org/10.1021/ja3034087.

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Diaz, C. G., et R. H. Tipping. « The Potential Energy Function for the X1Σ+ Ground State of CO ». Journal of Molecular Spectroscopy 163, n^o 1 (janvier 1994) : 58–66. http://dx.doi.org/10.1006/jmsp.1994.1006.

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Orel, Ann E., Yi Zhao et Oliver Kühn. « Laser driven ground state photodissociation of HCo(CO)4 : An ab initio quantum molecular dynamics approach ». Journal of Chemical Physics 112, n^o 1 (janvier 2000) : 94–100. http://dx.doi.org/10.1063/1.480564.

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Rudenko, Artem, Varun Makhija, Aram Vajdi, Thorsten Ergler, Markus Schürholz, Rajesh K. Kushawaha, Joachim Ullrich, Robert Moshammer et Vinod Kumarappan. « Strong-field-induced wave packet dynamics in carbon dioxide molecule ». Faraday Discussions 194 (2016) : 463–78. http://dx.doi.org/10.1039/c6fd00152a.

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Temporal evolution of electronic and nuclear wave packets created in strong-field excitation of the carbon dioxide molecule is studied employing momentum-resolved ion spectroscopy and channel-selective Fourier analysis. Combining the data obtained with two different pump-probe set-ups, we observed signatures of vibrational dynamics in both, ionic and neutral states of the molecule. We consider far-off-resonance two-photon Raman scattering to be the most likely mechanism of vibrational excitation in the electronic ground state of the neutral CO₂. Using the measured phase relation between the time-dependent yields of different fragmentation channels, which is consistent with the proposed mechanism, we suggest an intuitive picture of the underlying vibrational dynamics. For ionic states, we found signatures of both, electronic and vibrational excitations, which involve the ground and the first excited electronic states, depending on the particular final state of the fragmentation. While our results for ionic states are consistent with the recent observations by Erattupuzha et al. [J. Chem. Phys.144, 024306 (2016)], the neutral state contribution was not observed there, which we attribute to a larger bandwidth of the 8 fs pulses we used for this experiment. In a complementary measurement employing longer, 35 fs pulses in a 30 ps delay range, we study the influence of rotational excitation on our observables, and demonstrate how the coherent electronic wave packet created in the ground electronic state of the ion completely decays within 10 ps due to the coupling to rotational motion.

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