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Journal articles on the topic 'Polyatomic molecular spectra'

Author: Grafiati

Published: 4 June 2021

Last updated: 16 February 2022

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1

Larkins, FP, LC Tulea, and EZ Chelkowska. "Auger Electron Spectra of Molecules: The First Row Hydrides." Australian Journal of Physics 43, no. 5 (1990): 625. http://dx.doi.org/10.1071/ph900625.

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A semi-empirical molecular orbital approach primarily developed to predict the Auger energies and transition rates associated with complex polyatomic molecules has been evaluated by reference to the first row hydrides. For this suite of molecules, spanning a range of symmetry classes, high resolution experimental spectra and ab initio energy calculations are available for comparison. The method proposed provides a good first estimate for transition rates. Relative Auger energies are less satisfactory, especially when electron correlation effects are strong. Absolute kinetic energies are too low, principally due to the neglect of electronic relaxation. The usefulness of the approach is mainly for the interpretation of spectra for larger systems where ab initio calculations are not readily accomplished. A need for further experimental measurements obtained using photoelectron-Auger electron coincidence studies is identified to remove uncertainties associated with the extent of satellite contributions present in all the spectral profiles so far recorded. In the present work the satellite contribution to the methane Auger spectrum is estimated to be 16% of the total intensity compared with an earlier estimate in the literature of 49%.

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2

Borondo, F., J. M. Gomez Llorente, and R. M. Benito. "Theoretical Methods for the Analysis of Spectra of Highly Vibrationally Excited Polyatomic Molecules." Laser Chemistry 12, no. 1-2 (January 1, 1992): 85–102. http://dx.doi.org/10.1155/lc.12.85.

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The vibrational spectra of classically chaotic systems are usually very complicated and seemingly unassignable. In this paper, two methods for the analysis of spectra of highly vibrationally excited polyatomic molecules are described, and some results for the floppy molecules HCN and LiNC are presented. By application of these methods, relevant information on the underlying dynamics is obtained, thus establishing a bridge between the spectroscopy and the dynamics of these systems.

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3

Bonatsos, Dennis, and C. Daskaloyannis. "Vibrational molecular and nuclear spectra in terms of quantum algebras." HNPS Proceedings 4 (February 19, 2020): 121. http://dx.doi.org/10.12681/hnps.2879.

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A generalized deformed oscillator giving the same spectrum as the Morse potential is con structed through the use of quantum algebraic techniques. The model of n coupled anharmonic oscillators of Iachello and Oss, suitable for the description of vibrational spectra of polyatomic molecules, is subsequently written in terms of such generalized deformed oscillators. In addition to clarifying the relation of the model of Iachello and Oss to other models using coupled oscillators for the description of vibrational molecular spectra, the present formalism allows for the construction of a large class of exactly soluble models with no extra computational effort. As an example, the way of including a coupling of the Darling-Dennison type is shown. Nuclear models giving good descriptions of vibrational spectra are reviewed and the need of modifying the SUq(2) model in order to extend its region of applicability towards the vibrational limit is discussed.

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4

Alimpiev, S. S., and B. G. Sartakov. "The Spectral Features of Polyatomic Molecules Multiphoton Excitation in a Strong IR-Laser Field." Laser Chemistry 12, no. 3-4 (January 1, 1992): 147–72. http://dx.doi.org/10.1155/lc.12.147.

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The experimental data on multiphoton excitation of polyatomic molecules in strong fields of high pressure continuously tunable CO2 lasers are presented. The program package for computer simulation of multiphoton excitation spectra and excitation dynamics is developed. Good agreement between computer simulation and experimental data is observed.

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5

Yamanouchi, Kaoru, Jun Miyawaki, Soji Tsuchiya, David M. Jonas, and Robert W. Field. "New Scheme for Extracting Molecular Dynamics from Spectra: Case Study on Vibrationally Highly Excited Acetylene." Laser Chemistry 14, no. 1-3 (January 1, 1994): 183–90. http://dx.doi.org/10.1155/1994/34542.

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Three types of analyses: generalized conventional spectroscopic analysis, statistical analysis, and hierarchical analysis, by which we aim to extract dynamical information from the complex spectrum of small polyatomic molecules are reviewed by referring to recent studies on vibrationally highly excited acetylene. A convolution analysis, one type of hierarchical analysis, is performed on the dispersed fluorescence spectrum of acetylene to demonstrate its practical applicability. Based on previous studies, as well as on the convolution analysis, a systematic and efficient procedure to treat such complex spectra is discussed.

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6

Plíva, Josef. "On rotational resonances in the spectra of polyatomic molecules." Journal of Molecular Spectroscopy 120, no. 1 (November 1986): 5–10. http://dx.doi.org/10.1016/0022-2852(86)90066-4.

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7

Calero, S., B. Garzón, S. Jorge, Mejías, J. Tortajada, and S. Lago. "Suitability of the Kihara Potential To Predict Molecular Spectra of Linear Polyatomic Liquids." Journal of Physical Chemistry B 104, no. 24 (June 2000): 5808–15. http://dx.doi.org/10.1021/jp993904j.

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8

I McKay, Ruth, Evan J Bieske, Ian M Atkinson, Frederick R Bennett, Andrew J Bradley, Mark W Rainbird, Andrew B Rock, Angelo S Uichanco, and Alan EW Knight. "Spectroscopy and Structure of Aromatic?Rare Gas Cluster Ions." Australian Journal of Physics 43, no. 5 (1990): 683. http://dx.doi.org/10.1071/ph900683.

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Ionic clusters consisting of a polyatomic ion surrounded by a few 'solvent' atoms or molecules, provide a connecting link between the isolated gas phase ion and the ion solvated in a condensed medium. Analysis of the vibrational structure associated with the motion of the cluster atoms can reveal details concerning the intermolecular potential. However, for large polyatomic ions, information concerning the cluster vibrational motion has been difficult to obtain using conventional spectroscopic methods. We have developed a new combination of the previously available techniques of supersonic cooling, resonance-enhanced multi photon ionisation, timeof- flight mass spectroscopy, in concert with one-photon photodissociation spectroscopy. This new technique takes advantage of the facile predissociation of an electronically excited cluster and affords us a method of studying the previously unmeasurable vibrational structure associated with the motion of a molecular cluster ion. Using this technique we have obtained vibrationally resolved photodissociation spectra of a number of aromatic-rare gas cluster ions. Analysis of their vibrational structure permits structural details of the cluster cation to be deduced.

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9

Alcolea Palafox, Mauricio, and V. K. Rastogi. "Quantum chemical predictions of the vibrational spectra of polyatomic molecules." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 58, no. 3 (February 2002): 411–40. http://dx.doi.org/10.1016/s1386-1425(01)00509-1.

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10

Maring, W., and J. P. Toennies. "High Resolution Proton Energy Loss Spectroscopy of High Overtone Levels of Polyatomic Molecules." Laser Chemistry 11, no. 3-4 (January 1, 1991): 247–52. http://dx.doi.org/10.1155/lc.11.247.

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In the inelastic scattering of nearly monoenergetic proton beams (≅ 20 e V) from polyatomic molecules such as CF4 sharp peaks are observed corresponding to the excitation of very high overtone levels (n ≤ 14) of the infrared active modes. The collision mechanism leading to the high degree of excitation is described and an example from recent experiments is presented. A fit of the CF4 spectra provides new anharmonicity constants for the ν3-mode.

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11

Seltzer, Michael D. "Continuous Air Monitoring Using Inductively Coupled Plasma Atomic Emission Spectrometry: Correction of Spectral Interferences Arising from CN Emission." Applied Spectroscopy 52, no. 2 (February 1998): 195–99. http://dx.doi.org/10.1366/0003702981943482.

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Introduction of sample stream air into an argon inductively coupled plasma permits continuous monitoring of hazardous air pollutant metals in combustion flue gases. Along with entrained particulates and metal vapors, various molecular components of the flue gas are introduced into the plasma. These species, and reaction products thereof, also undergo excitation resulting in complex emission spectra of appreciable intensity. Serious spectral interferences arise for several metal elements, from molecular emission bands associated with the stable CN radical and other polyatomic species. Failure to account for these interferences can significantly degrade accuracy particularly at low flue gas metal concentrations. Reported here is an effective method for measurement and correction of CN spectral interferences affecting the on-line detection of hazardous air pollutant metals that incorporates conventional polychromator hardware and existing instrument software capabilities. A demonstration of the ability of this method to achieve virtually complete correction of these interferences under both laboratory and field conditions is presented.

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12

Yamanouchi, Kaoru, and Robert W. Field. "Short Time Dynamics of Highly Excited Small Polyatomic Molecules Extracted From Laser Spectra." Laser Chemistry 16, no. 1 (January 1, 1995): 31–41. http://dx.doi.org/10.1155/1995/36349.

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The recent spectroscopic investigations of vibrational dynamics of highly excited acetylene (C2H2), predissociation of vibronically excited NO2, and direct dissociation of OCS in the deep vacuum ultraviolet region are introduced. It is demonstrated that (i) rich and specific information on the excited state dynamics is encoded in various types of observed spectra such as stimulated emission pumping, dispersed fluorescence, laser induced fluorescence, absorption, and photofragment excitation spectra and that (ii) the early stage dynamics after photoexcitation can be extracted from observed spectra by the recently developed techniques, i.e. feature state assignments, a superpolyad Hamiltonian model, the extended autocorrelation method, and hierarchical, statistical and Fourier transform analysis methods.

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13

McCoy, Anne B., and Edwin L. Sibert. "An algebraic approach to calculating rotation-vibration spectra of polyatomic molecules." Molecular Physics 77, no. 4 (November 1992): 697–708. http://dx.doi.org/10.1080/00268979200102711.

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14

Demchuk, Yu S. "Characteristic features of electronic and vibrational spectra of free polyatomic molecules." Optics and Spectroscopy 95, no. 5 (November 2003): 690–95. http://dx.doi.org/10.1134/1.1628716.

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15

Farantos, S. C., J. M. Gomez Llorente, O. Hahn, and H. S. Taylor. "Classical dynamical analysis of the vibrational spectra for small polyatomic molecules." International Journal of Quantum Chemistry 38, S24 (March 17, 1990): 429–46. http://dx.doi.org/10.1002/qua.560382443.

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16

Wu, Lei, Craig White, Thomas J. Scanlon, Jason M. Reese, and Yonghao Zhang. "A kinetic model of the Boltzmann equation for non-vibrating polyatomic gases." Journal of Fluid Mechanics 763 (December 9, 2014): 24–50. http://dx.doi.org/10.1017/jfm.2014.632.

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AbstractA kinetic model of the Boltzmann equation for non-vibrating polyatomic gases is proposed, based on the Rykov model for diatomic gases. We adopt two velocity distribution functions (VDFs) to describe the system state; inelastic collisions are the same as in the Rykov model, but elastic collisions are modelled by the Boltzmann collision operator (BCO) for monatomic gases, so that the overall kinetic model equation reduces to the Boltzmann equation for monatomic gases in the limit of no translational–rotational energy exchange. The free parameters in the model are determined by comparing the transport coefficients, obtained by a Chapman–Enskog expansion, to values from experiment and kinetic theory. The kinetic model equations are solved numerically using the fast spectral method for elastic collision operators and the discrete velocity method for inelastic ones. The numerical results for normal shock waves and planar Fourier/Couette flows are in good agreement with both conventional direct simulation Monte Carlo (DSMC) results and experimental data. Poiseuille and thermal creep flows of polyatomic gases between two parallel plates are also investigated. Finally, we find that the spectra of both spontaneous and coherent Rayleigh–Brillouin scattering (RBS) compare well with DSMC results, and the computational speed of our model is approximately 300 times faster. Compared to the Rykov model, our model greatly improves prediction accuracy, and reveals the significant influence of molecular models. For coherent RBS, we find that the Rykov model could overpredict the bulk viscosity by a factor of two.

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17

Nikitin, A., J. P. Champion, and Vl G. Tyuterev. "The MIRS computer package for modeling the rovibrational spectra of polyatomic molecules." Journal of Quantitative Spectroscopy and Radiative Transfer 82, no. 1-4 (November 2003): 239–49. http://dx.doi.org/10.1016/s0022-4073(03)00156-0.

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18

Nonose, Naoko S., Naoki Matsuda, Noriko Fudagawa, and Masaaki Kubota. "Some characteristics of polyatomic ion spectra in inductively coupled plasma mass spectrometry." Spectrochimica Acta Part B: Atomic Spectroscopy 49, no. 10 (September 1994): 955–74. http://dx.doi.org/10.1016/0584-8547(94)80084-7.

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19

Chigiryov, A. R. "Vibronic spectra of polyatomic molecules in the adiabatic approximation: The direct spectroscopic problem." Journal of Molecular Spectroscopy 115, no. 2 (February 1986): 419–29. http://dx.doi.org/10.1016/0022-2852(86)90056-1.

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20

Chigiryov, A. R. "Vibronic spectra of polyatomic molecules in the adiabatic approximation: The inverse spectroscopic problem." Journal of Molecular Spectroscopy 115, no. 2 (February 1986): 430–37. http://dx.doi.org/10.1016/0022-2852(86)90057-3.

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21

Bersuker, B. "Quantum Chemistry in Moldova – 50 Years." Chemistry Journal of Moldova 4, no. 1 (June 2009): 36–43. http://dx.doi.org/10.19261/cjm.2009.04(1).14.

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An overview of the main achievements of the Laboratory of Quantum Chemistry of the Institute of Chemistry of the Academy of Sciences of Moldova during the 50 year of its existence is briefly outlined. The main fundamental non-transient result obtained in this laboratory is the generalization of the Jahn-Teller effect theory formulated and proved as a general law of instability of polyatomic systems and its application to a variety of physical, chemical, and biological problems, including al-range spectroscopy, geometry and spectra of molecular systems, structural phase transitions, ferroelectricity, stereochemistry and crystal chemistry, chemical activation and reactivity, electron transfer in mixed-valence compounds, and electron-conformational transitions in biological systems.

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22

Jørgensen, Uffe Gråe. "Molecular Data for Stellar Opacities." Highlights of Astronomy 10 (1995): 576–78. http://dx.doi.org/10.1017/s1539299600012107.

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In total, 40 neutral diatomic molecules, 2 molecular ions, and 7 polyatomic molecules are known from observed photospheric stellar spectra. Line data for opacity computations (i.e., lists of line frequencies, intensities, and excitation energies) exist for 17 of these molecules, although the data are complete only for a handful of them. A detailed description of stellar photospheric molecules can be found in Tsuji (1986), and the existing opacity data have been reviewed by Jorgensen (1995).Listed line frequencies in the data bases are either the measured values, or based on computed molecular constants obtained from fits to measured values. Attempts to compute ab initio line frequencies have so far resulted in lower accuracy than what is obtained by use of molecular constants. Published line strengths include measured values as well as ab initio values. For strong bands the ab initio intensities are as accurate as the laboratory values, whereas measured values for weak bands are generally more accurate than the ab initio values. The primary advantage of ab initio computations is therefore that the complete set of all transitions can be obtained. Exploratory studies have shown that completeness of the line data is crucial for the obtained stellar photospheric structure.As an alternative to the ab initio computations of the line intensities, fits to experimental data have been attempted. The most promising method seems to be to fit the dipole function by use of a Padé approximant. Combined with a potential fitted to experimental energy levels, such a dipole function can in principle be used to predict the complete list of band intensities and line intensities for all bands with energies up to the molecular dissociation energy. The part of the dipole function which corresponds to the largest stretching (or bending) of the molecule is the most uncertain in such fits as well as in ab initio computations. This part is responsible for most of the many weak transitions, and large uncertainties are therefore to be excepted in the computed intensities of the weak spectral bands. As these are of major importance for the stellar photospheric structure (due to their huge number and their pseudo continuous appearance in the spectrum), a particularly large effort is desirable in comparing computed intensities with laboratory data for a representative sample of weak bands. Unfortunately, only few measurements of weak bands exist.

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23

Smith, W. L. "Intensities of Transitions in Non-Totally Symmetric Vibrations in the Electronic Spectra of Polyatomic Molecules." Journal of Molecular Spectroscopy 176, no. 1 (March 1996): 95–98. http://dx.doi.org/10.1006/jmsp.1996.0065.

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24

Kamiński, Tomek, Karl M. Menten, Romuald Tylenda, Ka Tat Wong, Arnaud Belloche, Andrea Mehner, Mirek R. Schmidt, and Nimesh A. Patel. "Molecular remnant of Nova 1670 (CK Vulpeculae)." Astronomy & Astrophysics 644 (December 2020): A59. http://dx.doi.org/10.1051/0004-6361/202038648.

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CK Vul erupted in 1670 and is considered a Galactic stellar-merger candidate. Its remnant, observed 350 yr after the eruption, contains a molecular component of surprisingly rich composition, including polyatomic molecules as complex as methylamine (CH3NH2). We present interferometric line surveys with subarcsec resolution with ALMA and SMA. The observations provide interferometric maps of molecular line emission at frequencies between 88 and 243 GHz that allow imaging spectroscopy of more than 180 transitions of 26 species. We present, classify, and analyze the different morphologies of the emission regions displayed by the molecules. We also perform a non-LTE radiative-transfer analysis of emission of most of the observed species, deriving the kinetic temperatures and column densities in five parts of the molecular nebula. Non-LTE effects are clearly seen in complex species including methanol absorption against the cosmic microwave background. The temperatures are about 17 K in the inner remnant and 14 K in the extended lobes, both higher than excitation temperatures estimated earlier in an LTE approach and based on single-dish spectra. We find total (hydrogen plus helium) densities in the range of 104 − 106 cm−3. The column densities provide rough relative abundance patterns in the remnant which currently are not understood. Attempts to derive elemental abundances within the assumption of a chemical equilibrium give only loose constraints on the CNO elements. That the formation of many of the observed molecules requires a major involvement of circumstellar shocks remains the preferred possibility. The molecular gas could have formed 350 yr ago or more recently. The molecules are well shielded from the interstellar radiation field by the circumstellar dust. Their presence alone indicates that the unobservable central star cannot be a hot object such as a white dwarf. This excludes some of the proposed scenarios on the nature of CK Vul. The general characteristics of the molecular environment of CK Vul derived in this study resemble quite well those of some pre-planetary nebulae and asymptotic giant branch stars, most notably that of OH231.8+4.2.

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25

Pavlychev, A. A., A. S. Vinogradov, V. N. Akimov, and S. V. Nekipelov. "Quasiatomic treatment of near-edge-structure features in X-ray absorption spectra of first-row polyatomic systems." Physica Scripta 41, no. 1 (January 1, 1990): 160–63. http://dx.doi.org/10.1088/0031-8949/41/1/039.

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26

Burova, T. G., and A. A. Anashkin. "Quantum mechanical analysis of the intensity distribution in spectra of resonant hyper-Raman scattering of polyatomic molecules." Optics and Spectroscopy 108, no. 1 (January 2010): 12–15. http://dx.doi.org/10.1134/s0030400x10010030.

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27

Singh, Markandey, and Jai Prakash Chaturvedi. "Studies on Molecules of Astrophysical Interest." Publications of the Astronomical Society of Australia 9, no. 2 (1991): 328. http://dx.doi.org/10.1017/s1323358000024401.

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Extended abstractOur recent papers have been devoted to basic studies of diatomic and polyatomic molecules (Singh and Chaturvedi 1989 a,b,c,d; 1990a,b,c). A critical analysis of the 456 available references in literature has been made to select 135 polyatomic molecules, molecular ions and radicals containing from three to thirteen atoms of astrophysical significance. The results have been arranged in a text-cum-tabular form (Singh and Chaturvedi 1989 b,d). The compilation contains various information for each molecule, such as the spectral region, transition levels, and astrophysical objects where the respective molecules have been detected (say, comet, meteorite, Sun, planet, star, interstellar medium. Galaxy, etc.).

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28

Bencini, Alessandro, Antonio C. Fabretti, Claudia Zanchini, and Paolo Zannini. "Anisotropic exchange in dinuclear complexes with polyatomic bridges. Crystal and molecular structure and EPR spectra of (.mu.-oxalato)bis(1,10-phenanthroline)dicopper(II) dinitrate." Inorganic Chemistry 26, no. 9 (May 1987): 1445–49. http://dx.doi.org/10.1021/ic00256a024.

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29

Neville, Simon P., Vitali Averbukh, Serguei Patchkovskii, Marco Ruberti, Renjie Yun, Majed Chergui, Albert Stolow, and Michael S. Schuurman. "Beyond structure: ultrafast X-ray absorption spectroscopy as a probe of non-adiabatic wavepacket dynamics." Faraday Discussions 194 (2016): 117–45. http://dx.doi.org/10.1039/c6fd00117c.

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The excited state non-adiabatic dynamics of polyatomic molecules, leading to the coupling of structural and electronic dynamics, is a fundamentally important yet challenging problem for both experiment and theory. Ongoing developments in ultrafast extreme vacuum ultraviolet (XUV) and soft X-ray sources present new probes of coupled electronic-structural dynamics because of their novel and desirable characteristics. As one example, inner-shell spectroscopy offers localized, atom-specific probes of evolving electronic structure and bonding (via chemical shifts). In this work, we present the first on-the-fly ultrafast X-ray time-resolved absorption spectrum simulations of excited state wavepacket dynamics: photo-excited ethylene. This was achieved by coupling the ab initio multiple spawning (AIMS) method, employing on-the-fly dynamics simulations, with high-level algebraic diagrammatic construction (ADC) X-ray absorption cross-section calculations. Using the excited state dynamics of ethylene as a test case, we assessed the ability of X-ray absorption spectroscopy to project out the electronic character of complex wavepacket dynamics, and evaluated the sensitivity of the calculated spectra to large amplitude nuclear motion. In particular, we demonstrate the pronounced sensitivity of the pre-edge region of the X-ray absorption spectrum to the electronic and structural evolution of the excited-state wavepacket. We conclude that ultrafast time-resolved X-ray absorption spectroscopy may become a powerful tool in the interrogation of excited state non-adiabatic molecular dynamics.

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30

Smith, W. L. "The Strong Duschinsky Effect and the Intensity of Transitions in Non-Totally Symmetric Vibrations in the Electronic Spectra of Polyatomic Molecules." Journal of Molecular Spectroscopy 187, no. 1 (January 1998): 6–12. http://dx.doi.org/10.1006/jmsp.1997.7467.

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31

Chou, C. W., A. L. Collopy, C. Kurz, Y. Lin, M. E. Harding, P. N. Plessow, T. Fortier, S. Diddams, D. Leibfried, and D. R. Leibrandt. "Frequency-comb spectroscopy on pure quantum states of a single molecular ion." Science 367, no. 6485 (March 26, 2020): 1458–61. http://dx.doi.org/10.1126/science.aba3628.

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Spectroscopy is a powerful tool for studying molecules and is commonly performed on large thermal molecular ensembles that are perturbed by motional shifts and interactions with the environment and one another, resulting in convoluted spectra and limited resolution. Here, we use quantum-logic techniques to prepare a trapped molecular ion in a single quantum state, drive terahertz rotational transitions with an optical frequency comb, and read out the final state nondestructively, leaving the molecule ready for further manipulation. We can resolve rotational transitions to 11 significant digits and derive the rotational constant of 40CaH+ to be BR = 142 501 777.9(1.7) kilohertz. Our approach is suited for a wide range of molecular ions, including polyatomics and species relevant for tests of fundamental physics, chemistry, and astrophysics.

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32

PETROVIĆ, VIOLETA, V. BOČVARSKI, and I. PETROVIĆ. "EXPERT SYSTEM FOR THRESHOLD SPECTRA ANALYSIS OF SO2 MOLECULES." International Journal of Modern Physics C 18, no. 07 (July 2007): 1133–48. http://dx.doi.org/10.1142/s0129183107011170.

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In this paper an expert system is presented that was developed with the aim to analyze electron spectra on the threshold energies in collision with triatomic and polyatomic molecules. This expert system was made by updating the expert system for the analysis of the threshold spectra of two-atomic molecules. In contrast to the threshold spectra of two-atomic molecules, where were exist more or less defined structures of excited states, as well as vibrational levels, in the threshold spectra of triatomic molecules clearly defined structures almost do not exist. The application of the expert system in the process of triatomic and polyatomic molecules spectra analysis has an important role because it enables analysis of larger number of excited states, vibrational levels, and resonances, which can be missed in the analysis by classical methods, either because of low intensity or because of insufficiently defined separation of peaks in spectrum, which arise from the overlapping of a large number of peaks.

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33

Faure, Alexandre, Eric Josselin, Laurent Wiesenfeld, and Cecilia Ceccarelli. "Collisional excitation of complex organic molecules." Proceedings of the International Astronomical Union 4, S251 (February 2008): 137–38. http://dx.doi.org/10.1017/s1743921308021376.

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AbstractA major difficulty in modelling the infrared and (sub)millimeter spectra of gas-phase complex organic molecules is the lack of state-to-state collisional rate coefficients. Accurate quantum or classical scattering calculations for large polyatomic species are indeed computationally highly challenging, particularly when both rotation and low frequency vibrations such as bending and torsional modes are involved. We briefly present here an approximate approach to estimate and/or extrapolate rotational and rovibrational rates for polyatomic molecules with many degrees of freedom.

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34

Sapunar, Marin, Wolfgang Domcke, and Nađa Došlić. "UV absorption spectra of DNA bases in the 350–190 nm range: assignment and state specific analysis of solvation effects." Physical Chemistry Chemical Physics 21, no. 41 (2019): 22782–93. http://dx.doi.org/10.1039/c9cp04662c.

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35

Koç, Hüseyin. "Analytical Evaluation for Calculation of Two-Center Franck–Condon Factor and Matrix Elements." Journal of Chemistry 2018 (November 15, 2018): 1–6. http://dx.doi.org/10.1155/2018/3147981.

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The Franck–Condon (FC) factor is defined as squares of the Franck–Condon (FC) overlap integral and represents one of the principle fundamental factors of molecular physics. The FC factor is used to determine the transition probabilities in different vibrational levels of the two electronic states and the spectral line intensities of diatomic and polyatomic molecules. In this study, new analytical formulas were derived to calculate Franck–Condon integral (FCI) of harmonic oscillators and matrix elements (xη, e−2cx, and e−cx2) including simple finite summations of binomial coefficients. These formulas are valid for arbitrary values. The results of formulas are in agreement with the results in the literature.

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36

Carrington, Tucker. "Methods for calculating vibrational energy levels." Canadian Journal of Chemistry 82, no. 6 (June 1, 2004): 900–914. http://dx.doi.org/10.1139/v04-014.

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This article reviews new methods for computing vibrational energy levels of small polyatomic molecules. The principal impediment to the calculation of energy levels is the size of the required basis set. If one uses a product basis the Hamiltonian matrix for a four-atom molecule is too large to store in core memory. We discuss iterative methods that enable one to use a product basis to compute energy levels (and spectra) without storing a Hamiltonian matrix. Despite the advantages of iterative methods it is not possible, using product basis functions, to calculate vibrational spectra of molecules with more than four atoms. A very recent method combining contracted basis functions and the Lanczos algorithm with which vibrational energy levels of methane have been computed is described. New ideas, based on exploiting preconditioning, for reducing the number of matrix-vector products required to converge energy levels of interest are also summarized.Key words: vibrational energy levels, kinetic energy operators, Lanczos algorithm, contracted basis functions, preconditioning.

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37

PRINCE, K. C., R. RICHTER, M. DE SIMONE, and M. CORENO. "X-RAY ABSORPTION SPECTRA OF SOME SMALL POLYATOMIC MOLECULES." Surface Review and Letters 09, no. 01 (February 2002): 159–64. http://dx.doi.org/10.1142/s0218625x02002026.

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We report the Near Edge X-ray Absorption Fine Structure Spectra (NEXAFS) of a series of oxygen-containing organic molecules, namely formaldehyde, acetaldehyde, acetone, formic acid, methanol and dimethyl ether (DME), measured with high resolution at the carbon and oxygen edges. A vibrational progression has been observed at the oxygen 1s → π* resonance of formaldehyde, indicating that this state is bound with an excited state C=O stretching frequency of 136 meV. The spectra are compared with previous measurements and the applicability of the chromophore concept is tested for the functional groups present in these molecules.

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38

Patel, Nimesh A., Carl Gottlieb, Ken Young, Tomasz Kaminski, Michael McCarthy, Karl Menten, Chin-Fei Lee, and Harshal Gupta. "SMA Spectral Line Survey of the Proto-Planetary Nebula CRL 618." Proceedings of the International Astronomical Union 14, S343 (August 2018): 483–84. http://dx.doi.org/10.1017/s1743921318008104.

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AbstractCarbon-rich Asymptotic Giant Branch (AGB) stars are major sources of gas and dust in the interstellar medium. During the brief (∼1000 yr) period in the evolution from AGB to the Planetary Nebula (PN) stage, the molecular composition evolves from mainly diatomic and small polyatomic species to more complex molecules. Using the Submillimeter Array (SMA), we have carried out a spectral line survey of CRL 618, covering a frequency range of 281.9 to 359.4 GHz. More than 1000 lines were detected in the ∼60 GHz range, most of them assigned to HC3N and c-C3H2, and their isotopologues. About 200 lines are unassigned. Lines of CO, HCO+, and CS show the fast outflow wings, while the majority of line emission arises from a compact region of ∼1” diameter. We have analyzed the lines of HC3N, c-C3H2, CH3CN, and their isotopologues with rotation temperature diagrams.

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39

Islampour, Reza, Azam Khavaninzadeh, and Mahsasadat Miralinaghi. "Theoretical analysis of vibronic structure in absorption and fluorescence spectra of polyatomic molecules beyond the Condon approximation: Application to 11Ag↔21Ag and 11Ag↔11Bu electronic transitions in all-trans-1,3,5,7-octatetraene." Journal of Molecular Spectroscopy 286-287 (April 2013): 30–45. http://dx.doi.org/10.1016/j.jms.2013.02.005.

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40

Ajo, David, Alessandro Bencini, and Fabrizio Mani. "Anisotropic exchange in dinuclear complexes with polyatomic bridges. 2. Crystal and molecular structure and EPR spectra of tetraphenylphosphonium bis(.mu.-pyrazolato)bis[dihydrobis(1-pyrazolyl)borato](.mu.-chloro)dicuprate(II). Magneto-structural correlations in bis(.mu.-pyrazolato)-bridged copper(II) complexes." Inorganic Chemistry 27, no. 14 (July 1988): 2437–44. http://dx.doi.org/10.1021/ic00287a014.

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41

Hassan, Maab F., and Adil N. Ayyash. "Study of Spectral and Molecular Properties of Polyatomic molecule by Semiempirical and DFT Methods." Asian Journal of Research in Chemistry 12, no. 6 (2019): 330. http://dx.doi.org/10.5958/0974-4150.2019.00061.0.

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42

Huang, Xinchuan, David W. Schwenke, Timothy J. Lee, Keeyoon Sung, and Linda R. Brown. "Quantum IR line list of NH3 and isotopologues for ISM and dwarf studies." Proceedings of the International Astronomical Union 8, S292 (August 2012): 248. http://dx.doi.org/10.1017/s1743921313001233.

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AbstractAmmonia (NH3) was the first polyatomic molecule observed in the ISM. Its importance in interstellar molecules is only second to CO because its rovibrational spectroscopic signature can be used very effectively at deducing the conditions of the interstellar environment such as temperature and density, and because it is found in so many different interstellar objects in a wide temperature range. However, experimental determination of NH3 IR spectra is extremely difficult due to the large-amplutide inversion vibration, and the existing HITRAN2008 database for NH3 is limited in temperature, coverage, completeness, and accuracy. With rapid progress in theoretical chemistry and computational resources, now we are able to generate a highly reliable/accurate IR line list of NH3 (and its isotopologues) for astronomical studies. Exact quantum rovibrational computations on an empirically refined potential energy surface (with nonadiabatic corrections included) have achieved accuracies of 0.02-0.05 cm−1 (for line position) and better than 85-95% (for line intensity) for both NH3 and 15NH3 spectra. The unique feature of our work is that our predictions are essentially as accurate as reproducing existing measurements, suitable for synthetic simulation of various astrophysical environments or objects. The reliabilty and accuracy of our predictions for missing bands and higher energies computed on HSL-2 (Fig. 1) have been proved by the most recent high-resolution experiments and extended up to 7000 cm−1. See Huang et al. 2008, Huang et al. 2011, & Sung et al. 2012 for more details.

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43

Nishida, Yuzo. "Synthesis and Reactivity of Copper(II) Complexes with New Binucleating Ligands Derived from 16-or 20-Membered N4-Macrocycles." Zeitschrift für Naturforschung B 45, no. 1 (January 1, 1990): 39–44. http://dx.doi.org/10.1515/znb-1990-0109.

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Abstract New binucleating ligands, (L1) N ,N′,N″,N‴-tetrakis(2-benzimidazolylmethyl)-1,4,9,12-tetra-azacyclohexadecane, and (L2) N ,N′,N″,N‴-tetrakis(2-benzimidazolylmethyl)-1,4,11,14-tetra-azacycloeicosane were prepared. From the reaction mixture of copper(II) salt and the ligand, new binuclear copper(II) complexes, Cu2(L1) (NO3)4 (1), Cu2(L2)(NO3)4 (2), Cu2(L2)Br4 (3), and trinuclear complexes, Cu3(L1)Cl6 (4), and Cu3(L2)Cl6 (5) were obtained. Cyclic voltammograms revealed that the trinuclear complexes 4 and 5 are composed with the binuclear complex (1 or 2) and [CuCl4]2-. The interaction between two metal ions in the binuclear complexes are confirmed on the basis of the ESR spectra. These binuclear complexes exhibit higher catalytic activity for the oxidation of TMPD by O2 molecule than those of structurally rigid binuclear copper(II) complexes and of flexible binuclear complexes in which two copper(II) coordination sites are linked by a single polyatomic chain.

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44

Luttermoser, Donald G., and Hoilis R. Johnson. "The Violet Flux Deficiency of Cool Carbon Stars." International Astronomical Union Colloquium 106 (1989): 366. http://dx.doi.org/10.1017/s0252921100063247.

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A characteristic feature of carbon star spectra is the dramatic decrease in energy flux toward the violet. This flux decreases faster toward shorter wavelengths in N-type carbon stars than in either M giants or blackbodies of the same usual color temperatures, and an unknown violet opacity source in these carbon stars has consequently been the subject of speculation for the past 60 years. We investigate this longstanding problem of the violet flux falloff in cool carbon stars by directly testing, through synthetic spectra, the effects of many new and previously suggested opacity sources, based on currently available model atmospheres for carbon stars and M-giant stars. While several bound-free edges of neutral metals are important opacities, those of Na I at 2413 Å, Mg I at 2514 Å, and Ca I at 2940 Å are especially significant. Collectively, thousands of atomic lines, and in particular, the neutral metal resonance lines are the primary cause of the violet flux falloff. The severe violet flux decrease begins in cool carbon stars shortward of 4500 Å, roughly coincident with the redward wing of the extremely strong Ca I resonance line 4227 Å. The enormous line of Mg I at 2852 Å is one of the largest opacity sources in the near-ultraviolet region of these stars and influences the spectrum well into the visible. The pseudo-continuum of C3 and the photodissociation continuum of CH both play noticeable but secondary roles. Other opacities that may affect the violet flux include the photodissociation of other hydrides, particularly NH and SiH, which have dissociation energies similar to CH. Synthetic spectra from the carbon-star models computed both with and without polyatomic molecules fit nicely to the collected observations of the well-observed carbon star TX Pse.

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Shpenik, O., A. Zavilopulo, E. Remeta, S. Demes, and M. Erdevdy. "Inelastic Processes of Electron Interaction with Chalcogens in the Gaseous Phase (a Review)." Ukrainian Journal of Physics 65, no. 7 (July 15, 2020): 557. http://dx.doi.org/10.15407/ujpe65.7.557.

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Complex research of elementary pair collision processes occurring when low-energy (0–70 eV) electrons pass through chalcogen (S, Se, Te) vapor has been carried out in the evaporation temperature intervals of those elements (T = 320÷700 K for sulfur, 420÷490 K for selenium, and 400÷600 K for tellurium). The vapor compositions of indicated elements are studied using the mass spectroscopy method. The radiation spectra are analyzed in the wavelength interval from 200 to 600 nm with the help of optical spectroscopy. Using highly monoenergetic electron beams, the total (integral) formation cross-sections for positive and negative S, Se, and Te ions are measured. It is found that, under the experimental conditions, the main components of chalcogen vapor are molecules containing 2 to 8 atoms. At the energies of bombarding electrons below 10 eV, the emission spectra mainly consist of bands of diatomic molecules, and, at higher energies (E > 15 eV), there appear separate atomic and ionic lines. At E = 50 eV, the lines of singly charged ions are the most intense ones. It is shown that the most effective reaction channel is the interaction of electrons with diatomic molecules of indicated elements, whereas other processes are mainly associated with the decay of polyatomic molecules. The excitation and ionization thresholds for interaction products are found by analyzing the energy dependences of process characteristics. Specific features are also observed in the energy dependences of the excitation and ionization functions. Doubly charged ions of diatomic sulfur molecules, as well as selenium and tellurium atoms, are revealed for the first time. The appearance of triply charged ions of diatomic sulfur molecules is also detected. The main contribution to the total (integral) effective ionization cross-section of both positive and negative ions is proved to be made by the interaction processes of electrons with diatomic molecules S2, Se2, and Te2. Besides the experimental research, a detailed theoretical study is carried out. Calculations with a theoretical analysis of their results are performed for the structural characteristics of homoatomic sulfur, Sn, selenium, Sen, and tellurium, Ten, molecules with n = 2÷8; namely, interatomic distances, ionization potentials, electron affinity energies, and dissociation energies. The energy characteristics are applied to calculate the appearance energies for singly and doubly charged ionic fragments of those molecules at the dissociative ionization. The obtained results are carefully compared with the available experimental and theoretical data.

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46

Fujiki, Michiya, Julian R. Koe, and Seiko Amazumi. "Questions of Mirror Symmetry at the Photoexcited and Ground States of Non-Rigid Luminophores Raised by Circularly Polarized Luminescence and Circular Dichroism Spectroscopy. Part 2: Perylenes, BODIPYs, Molecular Scintillators, Coumarins, Rhodamine B, and DCM." Symmetry 11, no. 3 (March 11, 2019): 363. http://dx.doi.org/10.3390/sym11030363.

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We investigated whether semi-rigid and non-rigid π-conjugated fluorophores in the photoexcited (S1) and ground (S0) states exhibited mirror symmetry by circularly polarized luminescence (CPL) and circular dichroism (CD) spectroscopy using a range of compounds dissolved in achiral liquids. The fluorophores tested were six perylenes, six scintillators, 11 coumarins, two pyrromethene difluoroborates (BODIPYs), rhodamine B (RhB), and 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM). All the fluorophores showed negative-sign CPL signals in the ultraviolet (UV)–visible region, suggesting energetically non-equivalent and non-mirror image structures in the S1 state. The dissymmetry ratio of the CPL (glum) increased discontinuously from approximately −0.2 × 10−3 to −2.0 × 10−3, as the viscosity of the liquids increased. Among these liquids, C2-symmetrical stilbene 420 showed glum ≈ −0.5 × 10−3 at 408 nm in H2O and D2O, while, in a viscous alkanediol, the signal was amplified to glum ≈ −2.0 × 10−3. Moreover, BODIPYs, RhB, and DCM in the S0 states revealed weak (−)-sign CD signals with dissymmetry ratios (gabs) ≈ −1.4 × 10−5 at λmax/λext. The origin of the (−)-sign CPL and the (−)-sign CD signals may arise from an electroweak charge at the polyatomic level. Our CPL and CD spectral analysis could be a possible answer to the molecular parity violation hypothesis based on a weak neutral current of Z0 boson origin that could connect to the origin of biomolecular handedness.

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47

Acosta-Maeda, Tayro E., Anupam K. Misra, John N. Porter, David E. Bates, and Shiv K. Sharma. "Remote Raman Efficiencies and Cross-Sections of Organic and Inorganic Chemicals." Applied Spectroscopy 71, no. 5 (September 19, 2016): 1025–38. http://dx.doi.org/10.1177/0003702816668531.

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We determined Raman cross-sections of various organic liquids and inorganic polyatomic ions in aqueous solutions with a 532 nm pulsed laser using remote Raman systems developed at the University of Hawaii. Using a calibrated integrating sphere as a light source, we converted the intensity counts in the spectrum of the light from the integrating sphere measured with UH remote Raman instrument to spectral radiance. From these data, a response function of the remote Raman instrument was obtained. With the intensity-calibrated instrument, we collected remote Raman data from a standard 1 mm path length fused silica spectrophotometer cell filled with cyclohexane. The measured value of the differential Raman cross-section for the 801 cm−1 vibrational mode of cyclohexane is 4.55 × 10−30 cm2 sr−1 molecule−1 when excited by a 532 nm laser, in good agreement with the values reported in the literature. Using the measured cyclohexane Raman cross-section as a reference and relative Raman mode intensities of the various ions and organic liquids, we calculated the Raman cross-sections of the strongest Raman lines of nitrate, sulfate, carbonate, phosphate ions, and organic liquids by maintaining same experimental conditions for remote Raman detection. These relative Raman cross-section values will be useful for estimating detection capabilities of remote Raman systems for planetary exploration.

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48

Lomax-Vogt, Madeleine C., Fang Liu, and John W. Olesik. "A searchable/filterable database of elemental, doubly charged, and polyatomic ions that can cause spectral overlaps in inductively coupled plasma-mass spectrometry." Spectrochimica Acta Part B: Atomic Spectroscopy 179 (May 2021): 106098. http://dx.doi.org/10.1016/j.sab.2021.106098.

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49

"General discussion: electronic emission spectroscopy of CF+4 and SiF+4." Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 324, no. 1578 (January 26, 1988): 289–93. http://dx.doi.org/10.1098/rsta.1988.0018.

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We report the observation of electronic emission spectra in the tetrahedral molecular ions CF+4 and SiF+4. The spectra are observed at a low rotational temperature (less than 30 K) in a crossed molecular-beam - electron-beam apparatus (Carrington & Tuckett 1980). These spectra are especially interesting because the fluorescing states in the two ions lie up to 10 eV above their lowest dissociation channel (to CF+3/SiF+3 + F; see figure 1), and these states might be expected to decay non-radiatively rather than by a radiative channel. The observation of fluorescence decay from highly excited electronic states of these polyatomic ions is therefore a very surprising phenomenon.

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BENCINI, A., A. C. FABRETTI, C. ZANCHINI, and P. ZANNINI. "ChemInform Abstract: Anisotropic Exchange in Dinuclear Complexes with Polyatomic Bridges. Crystal and Molecular Structure and EPR Spectra of (μ-Oxalato)bis(1,10-phenanthroline)dicopper(II) Dinitrate." ChemInform 18, no. 36 (September 8, 1987). http://dx.doi.org/10.1002/chin.198736061.

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