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Auteur : Grafiati
Publié le 7 septembre 2023

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1

Numico, R., A. Keller et O. Atabek. « Laser-induced molecular alignment in dissociation dynamics ». Physical Review A 52, no 2 (1 août 1995) : 1298–309. http://dx.doi.org/10.1103/physreva.52.1298.

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2

Kato, Shuji, Yoshihiro Makide, Takeshi Tominaga et Kazuo Takeuchi. « Infrared Multiphoton Dissociation of CF3CHClF : Primary Dissociation and Secondary Photolysis ». Laser Chemistry 8, no 2-4 (1 janvier 1988) : 211–34. http://dx.doi.org/10.1155/lc.8.211.

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The dissociation yield and branching ratio in CO2 laser-induced infrared multiphoton dissociation (IRMPD) of CF3CHClF were investigated by irradiation at 9R(20) 1078.6 cm−1 under an unfocused irradiation geometry (0.75-2.3 J/cm2) and a mildly focused one (1.2-18 J/cm2). By using a Br2-scavenging technique, it was revealed that the primary dissociation of CF3CHClF proceeded mainly via three-centered HCl molecular elimination and C-Cl bond rupture, with minor contributions of C-C bond rupture and HF molecular elimination at higher fluences. The secondary photolysis of the primarily produced species during the laser pulse to yield CF2 and CClF carbenes depended strongly upon the laser fluence.
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3

He, X., O. Atabek et A. Giusti-Suzor. « Laser-induced resonances in molecular dissociation in intense fields ». Physical Review A 38, no 11 (1 décembre 1988) : 5586–94. http://dx.doi.org/10.1103/physreva.38.5586.

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4

Akram, M., Raheel Ali et M. A. Baig. « Laser induced molecular dissociation and ionization of potassium vapour ». Optics Communications 136, no 5-6 (avril 1997) : 390–94. http://dx.doi.org/10.1016/s0030-4018(96)00713-4.

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5

Hoang Man, Viet, Nguyen-Thi Van-Oanh, Philippe Derreumaux, Mai Suan Li, Christopher Roland, Celeste Sagui et Phuong H. Nguyen. « Picosecond infrared laser-induced all-atom nonequilibrium molecular dynamics simulation of dissociation of viruses ». Physical Chemistry Chemical Physics 18, no 17 (2016) : 11951–58. http://dx.doi.org/10.1039/c5cp07711g.

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6

Csehi, András, Gábor J. Halász, Lorenz S. Cederbaum et Ágnes Vibók. « Towards controlling the dissociation probability by light-induced conical intersections ». Faraday Discussions 194 (2016) : 479–93. http://dx.doi.org/10.1039/c6fd00139d.

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Light-induced conical intersections (LICIs) can be formed both by standing or by running laser waves. The position of a LICI is determined by the laser frequency while the laser intensity controls the strength of the nonadiabatic coupling. Recently, it was shown within the LICI framework that linearly chirped laser pulses have an impact on the dissociation dynamics of the D2+molecule (J. Chem. Phys.,143, 014305, (2015);J. Chem. Phys.,144, 074309, (2016)). In this work we exploit this finding and perform calculations using chirped laser pulses in which the time dependence of the laser frequency is designed so as to force the LICI to move together with the field-free vibrational wave packet as much as possible. Since nonadiabaticity is strongest in the vicinity of the conical intersection, this is the first step towards controlling the dissociation processviathe LICI. Our showcase example is again the D2+molecular ion. To demonstrate the impact of the LICIs on the dynamical properties of diatomics, the total dissociation probabilities and the population of the different vibrational levels after the dissociation process are studied and discussed.
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7

Abeln, B., J. V. Hernández, F. Anis et B. D. Esry. « Comparison of theoretical analyses of intense-laser-induced molecular dissociation ». Journal of Physics B : Atomic, Molecular and Optical Physics 43, no 15 (7 juillet 2010) : 155005. http://dx.doi.org/10.1088/0953-4075/43/15/155005.

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8

Lai, G. D., Y. L. Zhao, S. N. Luo et J. C. Shi. « Influence of the molecular structure on heterocyclic-ring dissociation kinetics and structural evolution of laser-induced plasmas ». Journal of Analytical Atomic Spectrometry 36, no 8 (2021) : 1742–49. http://dx.doi.org/10.1039/d1ja00166c.

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Exploring the influence of the molecular structure on the dissociation kinetics and structural evolution of heterocyclic rings in fs laser-induced plasma based on temporally and spatially resolved measurements.
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9

Alexander, J. D., C. R. Calvert, R. B. King, O. Kelly, W. A. Bryan, G. R. A. J. Nemeth, W. R. Newell et al. « Short pulse laser-induced dissociation of vibrationally cold, trapped molecular ions ». Journal of Physics B : Atomic, Molecular and Optical Physics 42, no 15 (16 juillet 2009) : 154027. http://dx.doi.org/10.1088/0953-4075/42/15/154027.

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10

Zhang, Wei, Lirong Bao, Kexin Jiang, Anran Shi, Ruiqi Shen et Yinghua Ye. « Identification and formation mechanism of the transient ion fragments produced in laser-induced dissociation of 1, 1-diamino-2, 2-dinitroethylene ». Laser and Particle Beams 36, no 3 (septembre 2018) : 308–12. http://dx.doi.org/10.1017/s0263034618000290.

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AbstractDetailed knowledge of dissociation behavior and dissociation products is necessary to understand the stability, sensitivity, and the reactive mechanism of explosives under laser initiation. A time-of-flight mass spectrometer was utilized to detect the transient products of 1,1-diamino-2,2-dinitroethylene (FOX-7) produced under 532 nm pulse laser ablation, the possible attribution of intermediate ion fragments were confirmed. The laser fluence threshold for detectable fragments is about 3.6 J/cm2. The peak intensities of main ions (CN, CNO/C2H4N, NO2, C2N2O, HCN, C2NH2, etc.) increase with the increasing of laser fluence, and reach the maximum at 11.5 J/cm2. Moreover, time-depend changes of ion intensity indicate that the type and degree of reactions are different in different periods. According to the molecular structure of FOX-7 and the intermediate ions, the laser-induced dissociation mechanisms were proposed to illustrate the cause of the fragments which might throw some light on the laser initiation of FOX-7.
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11

Akram, M., et M. A. Baig. « Laser-induced dissociation and ionization of lithium vapour ». Journal of Physics B : Atomic, Molecular and Optical Physics 29, no 10 (28 mai 1996) : L381—L387. http://dx.doi.org/10.1088/0953-4075/29/10/001.

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12

Fantoni, R., F. Bijnen, N. Djurić et S. Piccirillo. « Cars Diagnostic on a Photochemical Reactor for IR Laser Induced Production of Si and Si3N4 Powders ». Laser Chemistry 11, no 1 (1 janvier 1991) : 13–30. http://dx.doi.org/10.1155/lc.11.13.

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In a flow reactor a low power (up to 50 W) CW CO2 laser tuned at 944,19 cm−1 has been focussed in order to produce Si and Si3N4 ultrafine powders from SiH4 and SiH4/NH3 mixtures.Among possible on-line optical diagnostics, two different CARS techniques have been used to monitor the excitation process and to measure average reaction temperatures in collinear geometry. In broad-band CARS at low resolution (≈6.0 cm−1) the reactant temperature is measured from the attenuation of the corresponding integrated peak intensity below and at the dissociation threshold. In narrow-band experiments the temperature reached by the dissociating reactants below and above the threshold is inferred from the spectral shape (measured with 0.2 cm−1 resolution) of the envelope of rovibrational CARS transitions involved.Results obtained at the threshold for SiH4 dissociation are in agreement with previous data on gas-phase pyrolysis in a thermal process. For the SiH4/NH3 reaction the difficulty in obtaining stoichiometric Si3N4 has been related to the cooling effect of large NH3 addition to the SiH4 warmed up in the laser absorption.
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13

Laptev, V. B., L. M. Tumanova et E. A. Ryabov. « Selective IR Laser Induced Isomerization and Dissociation of BIS (Trifluoromethyl) Ketene Molecules ». Laser Chemistry 16, no 4 (1 janvier 1996) : 255–64. http://dx.doi.org/10.1155/1996/34032.

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Multiphoton IR laser induced isomerization and dissociation of (CF3)2C=C=O (FMK) molecules have been studied. The antisymmetric stretch v1 = 2192 cm-1 of C=C=O—and antisymmetric v16 = 991 cm-1 of C—C— bonds were excited by the second- and first harmonics of a pulsed TEA CO2 laser. The dependence of isomerization conversion on laser radiation frequency, fluence, and number of shots was measured. The isomerization channel was predominant compared with dissociation for the conditions of IR multiphoton excitation under study.The isomerization of FMK by the second–harmonic radiation of a CO2 laser was proved to be selective with respect to oxygen isotopes. The isomerization product (FMA molecules) was enriched with 18O with maximum value of selectivity α(18/16) = 3.9 when FMK molecules were excited at 2ωlas = 2143.8 cm-1.
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14

Makarov, G. N., et A. N. Petin. « TEA CO2 laser-induced selective molecular dissociation in a cold shock wave ». Journal of Experimental and Theoretical Physics Letters 71, no 10 (mai 2000) : 399–402. http://dx.doi.org/10.1134/1.568363.

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15

GRAHAM, P., X. FANG, K. W. D. LEDINGHAM, R. P. SINGHAL, T. McCANNY, D. J. SMITH, C. KOSMIDIS, P. TZALLAS, A. J. LANGLEY et P. F. TADAY. « Unusual fragmentation patterns from the dissociation of some small molecules ». Laser and Particle Beams 18, no 3 (juillet 2000) : 417–32. http://dx.doi.org/10.1017/s0263034600183107.

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The nonlinear interaction of molecular matter with the intense field of a linearly-polarized laser beam, allows the study of not only the ionization dynamics of the parent molecule, but also the angular distribution of the exploding fragments. This is carried out by rotating the polarization vector of the laser with respect to the laboratory reference frame. The angular distributions for the CS2, CO2, N2O, H2S, and CH3I molecular ions, at intensities of about 1016 W cm−2, are presented. The distributions seem to be dependent on the molecule under consideration, but common features are that the peripheral atoms of the molecule are ejected along the ToF-axis, and the central atom perpendicularly to it, whenever the polarization vector and ToF-axis are collinear. It would seem that the distributions for the lighter of the molecules are partly due to alignment via dipole moments induced by the laser, as the distributions narrow as their charge-state increases. This is indicative of a larger torque acting on the higher-charged precursor molecular ion, via the interaction of the field with the laser-induced dipole moment. On the other hand, the angular dependence of the heavier molecules studied, are thought to originate from a dependence of the ionization/dissociation probability of the molecular ion on the initial angle made between the molecular axis and the polarization vector, that is, a preferential ionization/dissociation process. Spatial alignment in the laser pulse, in this case, is not thought to occur since the peaks do not narrow as the ionic charge increases. Finally, the results for H2S and also N2O are particularly interesting, since distributions for up to S7+ are presented, while the N-distributions show both a parallel and perpendicular component of the distribution. Neither of these results has, to the author's knowledge, been previously observed.
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16

Bagratashvili, V. N., M. V. Kuzmin et V. S. Letokhov. « Kinetics of Nonequilibrium Gas Phase Reactions Induced by Vibrational Multiple-Photon IR Laser Excitation of Molecules ». Laser Chemistry 7, no 1 (1 janvier 1987) : 1–27. http://dx.doi.org/10.1155/lc.7.1.

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A simple theoretical model for the qualitative description of the kinetics of the unimolecular decay in the pulsed IR laser field with strong deviation from thermal equilibrium is developed. The nonequilibrium character of the reaction is introduced by means of a special parameter of “truncation” of vibrational energy distribution function, which takes into account depletion of the distribution function due to the dissociation. The derived self-consistent system of differential equations describes the three dissociation regimes. Besides, the apparent cases of collisionless (short duration of laser pulse τp) and equilibrium (long τp) reactions, the intermediate collisional-nonequilibrium dissociation is revealed. The contribution of postpulse reaction has proved considerable in case of both long and short pulses. For the case of a successive dissociation the possibility of synthesis of labile products which cannot be produced at thermal initiation is established.
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17

Miles, Richard B., James B. Michael, Christopher M. Limbach, Sean D. McGuire, Tat Loon Chng, Matthew R. Edwards, Nicholas J. DeLuca, Mikhail N. Shneider et Arthur Dogariu. « New diagnostic methods for laser plasma- and microwave-enhanced combustion ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 373, no 2048 (13 août 2015) : 20140338. http://dx.doi.org/10.1098/rsta.2014.0338.

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The study of pulsed laser- and microwave-induced plasma interactions with atmospheric and higher pressure combusting gases requires rapid diagnostic methods that are capable of determining the mechanisms by which these interactions are taking place. New rapid diagnostics are presented here extending the capabilities of Rayleigh and Thomson scattering and resonance-enhanced multi-photon ionization (REMPI) detection and introducing femtosecond laser-induced velocity and temperature profile imaging. Spectrally filtered Rayleigh scattering provides a method for the planar imaging of temperature fields for constant pressure interactions and line imaging of velocity, temperature and density profiles. Depolarization of Rayleigh scattering provides a measure of the dissociation fraction, and multi-wavelength line imaging enables the separation of Thomson scattering from Rayleigh scattering. Radar REMPI takes advantage of high-frequency microwave scattering from the region of laser-selected species ionization to extend REMPI to atmospheric pressures and implement it as a stand-off detection method for atomic and molecular species in combusting environments. Femtosecond laser electronic excitation tagging (FLEET) generates highly excited molecular species and dissociation through the focal zone of the laser. The prompt fluorescence from excited molecular species yields temperature profiles, and the delayed fluorescence from recombining atomic fragments yields velocity profiles.
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18

Wu, Chengyin, Haizhen Ren, Tingting Liu, Ri Ma, Hong Yang, Hongbing Jiang et Qihuang Gong. « Laser-induced dissociation and explosion of methane and methanol ». Journal of Physics B : Atomic, Molecular and Optical Physics 35, no 11 (24 mai 2002) : 2575–82. http://dx.doi.org/10.1088/0953-4075/35/11/315.

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19

Atabek, O. « Laser-induced alignment dynamics in multiphoton dissociation of H2+ ». International Journal of Quantum Chemistry 65, no 5 (1997) : 617–24. http://dx.doi.org/10.1002/(sici)1097-461x(1997)65:5<617 ::aid-qua27>3.0.co;2-y.

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20

Hoheisel, W., U. Schulte, M. Vollmer et F. Tr�ger. « Optical spectra and laser-induced dissociation of supported Na particles ». Zeitschrift f�r Physik D Atoms, Molecules and Clusters 20, no 1-4 (mars 1991) : 381–83. http://dx.doi.org/10.1007/bf01544016.

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21

Mitrofanov, Elena, Tassilo Muskat et Jürgen Grotemeyer. « Indocyanine green MS/MS investigations using femtosecond laser-pulse photodissociation and collision-induced dissociation ». European Journal of Mass Spectrometry 24, no 3 (25 décembre 2017) : 299–312. http://dx.doi.org/10.1177/1469066717750044.

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The dissociation reactions of indocyanine green (also known as cardiogreen) have been studied in a Fourier-transform ion-cyclotron resonance mass spectrometer by the application of unimolecular, collision-induced dissociation and photodissociation using femtosecond laser pulses. Ions were prepared by electrospray ionization (ESI) in various solvents. Depending on the properties of the solvent mixture, the mono sodiated molecule could be measured through cation exchange in various compositions. Using a mixture of methanol/water/formic acid as solvent, protonated ions, formed by exchange of sodium, are predominantly observed. A mixture of isopropanol/formic acid leads to the addition of a further sodium cation to the molecule yielding an intense bi-sodiated ion signal. The photodissociation of the stored ions was achieved using pulses at a wavelength of 790 nm and approximately 150 fs pulse duration. The results show that only fs-photodissociation leads to the fragmentation of the different molecular structures, while in case of sodiated indocyanine green collision induced dissociation fails completely to observe any fragments. In all other investigated ion structures, the collision-induced-dissociation spectra show unspecified and little intense spectra. It is shown that fs-photodissociation mass spectrometry is the only method that leads to substance specific fragmentation for this sample. Furthermore, indocyanine green is known to form aggregation products. In the ion-cyclotron resonance experiment, the reactions of a dimeric cluster were also investigated. The necessary condition and the interference of the fragmentations with those of the monomer are discussed.
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22

Castillejo, M., M. Martín et R. de Nalda. « Nanosecond Versus, Picosecond Molecular Multiphoton Fragmentation of Ketene and Cyclohexane ». Laser Chemistry 18, no 1-2 (1 janvier 1998) : 51–62. http://dx.doi.org/10.1155/1998/25701.

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Multiphoton dissociation of ketene was studied at 290.5 nm after irradiation of the first excited singlet state with two different laser pulsewidths of 4 ns and 10 ps. Analysis of the photofragment fluorescence spectra in the two time domains sheds light on the mechanisms that are responsible for the production of the observed CH(A2Δ), (B2Σ−) and C2(d3Πg) photofragments. Multiphoton ionization of cyclohexane induced by a visible laser at 581 nm and its second harmonic at 290.5 nm was measured in the above mentioned pulse duration regimes. Study of the dependence of the total ionization signal on pressure and laser energy helps to clarify the role played by the giant resonance of this molecule at 84000 cm-1 in the photoionization process.
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23

SCHMIDT, M., P. D'OLIVEIRA, P. MEYNADIER, D. NORMAND et C. CORNAGGIA. « STRONG LASER FIELD INTERACTION WITH DIATOMIC MOLECULES : FROM THE ULTRA-SHORT TO LONG-PULSE REGIME ». Journal of Nonlinear Optical Physics & ; Materials 04, no 04 (octobre 1995) : 817–29. http://dx.doi.org/10.1142/s0218863595000367.

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In the present paper, we compare novel MEDI results on iodine obtained with 30 ps laser pulses to those obtained in the femtosecond regime. The results indicate laser-induced trapping of the molecules not only in the ultra-short pulse regime, but also for the long pulses, since the fragment kinetic energy releases are essentially the same, although the pulse duration is varied over more than two orders of magnitude. Most interestingly, with 30 ps pulses significant post-dissociation ionization of the In+-fragments observed for the first time, proving that near-Coulomb energies and post-dissociation ionization can be observed simultaneously. A femtosecond double-pulse experiment confirms our recent hypothesis of molecular stabilization governing the MEDI interaction.
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24

Lokhman, V. N., G. N. Makarov, A. N. Petin, D. G. Poydashev et E. A. Ryabov. « Infrared Laser-Induced Isotope-Selective Dissociation of Molecular van der Waals (SF6)mArn Clusters ». Journal of Experimental and Theoretical Physics 128, no 2 (février 2019) : 188–98. http://dx.doi.org/10.1134/s106377611901014x.

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25

Yuan, Jian-Min, Yiwu Duan et Wing-Ki Liu. « Chemical Bonding in Hydrogen Molecular Ion and Competition between Laser-induced Ionization and Dissociation ». Journal of the Chinese Chemical Society 48, no 3 (juin 2001) : 491–97. http://dx.doi.org/10.1002/jccs.200100073.

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26

Guo, C. « Triple-ionization-induced dissociation of molecules in strong laser fields ». Laser Physics 19, no 8 (15 juillet 2009) : 1635–39. http://dx.doi.org/10.1134/s1054660x09150171.

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27

Carlomusto, L., A. Cartelli, S. Solimeno, R. Velotta et R. Bruzzese. « Experimental and Theoretical Analysis of Non-linear Vibrational Relaxation of Polyatomic Molecules Strongly Excited by Resonant Laser Radiation ». Laser Chemistry 8, no 2-4 (1 janvier 1988) : 315–34. http://dx.doi.org/10.1155/lc.8.315.

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We present a very simple theoretical model aimed at the analysis of non-linear relaxation processes in molecular gases in the presence of partial molecular dissociation induced by vibrational–vibrational exchange between highly excited molecules. The model has a phenomenological character, since it analyzes the behavior of a system of anharmonic diatomic molecules, which is a very rough approximation of a polyatomic molecule such as SF6. Nonetheless, it provides an interesting key for the interpretation of a number of peculiar features characterizing our experimental observation, with which a comparison is made. In particular, the model takes realistic account of the influence of dissociation processes on the relaxation time.
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28

Strek, Wieslaw, Przemysław Wiewiórski, Włodzimierz Miśta, Robert Tomala et Mariusz Stefanski. « Laser-Induced Generation of Hydrogen in Water by Using Graphene Target ». Molecules 27, no 3 (22 janvier 2022) : 718. http://dx.doi.org/10.3390/molecules27030718.

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A new method of hydrogen generation from water, by irradiation with CW infrared laser diode of graphene scaffold immersed in solution, is reported. Hydrogen production was extremely efficient upon admixing NaCl into water. The efficiency of hydrogen production increased exponentially with laser power. It was shown that hydrogen production was highly efficient when the intense white light emission induced by laser irradiation of graphene foam was occurring. The mechanism of laser-induced dissociation of water is discussed. It was found that hydrogen production was extremely high, at about 80%, and assisted by a small emission of O2, CO and CO2 gases.
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29

Riveros, José M., et Luis Gilberto Barreta. « A Time Resolved IR Laser Photolysis-Laser Induced Fluorescence Study of the OH/Methanol Reaction ». Laser Chemistry 16, no 2 (1 janvier 1995) : 53–61. http://dx.doi.org/10.1155/1995/86298.

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The reaction of hydroxyl radicals (OH and OD) generated by infrared multiphoton dissociation of different isotopomers of methanol were studied in the presence of variable amounts of Ar buffer gas. The disappearance of the OH, or OD, radicals in the presence of the parent methanol was followed by laser induced fluorescence at 310 nm. Comparison of the rate constants obtained from these experiments reveal good agreement with observed isotope effects observed by other authors but suggest that the reactions occurs at higher temperatures than the macroscopic bulk temperature of the sample.
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30

Varakin, V. N., et A. P. Simonov. « UV Laser Induced Chemistry of Adsorbed Dimethylcadmium ». Laser Chemistry 12, no 3-4 (1 janvier 1992) : 181–97. http://dx.doi.org/10.1155/lc.12.181.

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The UV laser chemistry of dimethylcadmium (DMCd) either chemisorbed at 297 K on n-type Si(100) with native oxide or physisorbed at 150 K on a photodeposited cadmium film has been studied by using mass spectrometry of desorbed species. A XeCl laser induced the heterogeneous fragmentation of these chemisorbed molecules as well as the desorption of DMCd, Cd, and CH3. The resonant absorption of a KrCl laser radiation by adsorbed DMCd led to their photolysis and the ejection of DMCd and its fragments in both neutral and ionic forms. The kinetic, laser fluence, and time-of-flight dependences of desorbed species have been measured to elucidate the mechanisms of the dissociative and desorption processes either induced by lasers or occurring spontaneously. The effects of these lasers on chemisorbed DMCd as well as KrCl laser assisted processes in chemisorbed and physisorbed molecules have been compared.
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31

Simakin, Aleksander V., Ilya V. Baimler, Alexey S. Baryshev, Anastasiya O. Dikovskaya et Sergey V. Gudkov. « The Influence of Gadolinium Oxide Nanoparticles Concentration on the Chemical and Physical Processes Intensity during Laser-Induced Breakdown of Aqueous Solutions ». Photonics 10, no 7 (5 juillet 2023) : 784. http://dx.doi.org/10.3390/photonics10070784.

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The paper investigates the physicochemical processes that occur during laser-induced breakdown in colloids of gadolinium oxide nanoparticles of different concentrations. A monotonic change in the number of optical breakdowns, the average distance between the nearest breakdowns in the track of a single laser pulse, the average plasma size of a single optical breakdown, the integral luminosity of an optical breakdown plasma flash, the intensity of acoustic signals, and the rate of formation of dissociation products—O2, H2, OH•, and H2O2—is demonstrated. It is shown that the rate of formation of chemical products of the decomposition of H2O molecules under the action of breakdown when using nanoparticles of rare earth metals, in particular, gadolinium oxide, is the highest compared to other materials. Based on one laser pulse, the rates of formation of chemical products formed during the dissociation of water during laser-induced breakdown of a colloid of gadolinium oxide nanoparticles are 13.13 nmol/pulse for H2, 5.41 nmol/pulse for O2, and 6.98 nmol/pulse for hydrogen peroxide.
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32

Wang, Dongxia, Philip A. Cole et Robert J. Cotter. « Laser-induced dissociation of phosphorylated peptides using matrix assisted laser desorption/ionization tandem time-of-flight mass spectrometry ». Clinical Proteomics 2, no 3-4 (décembre 2006) : 133–44. http://dx.doi.org/10.1007/bf02752496.

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33

YUAN, KAI-JUN, ZHENG-TANG LIU, JIE YU, MAO-DU CHEN et SHU-LIN CONG. « THEORETICAL STUDY OF ABOVE THRESHOLD DISSOCIATION OF HD+ IN FEMTOSECOND LASER FIELDS ». Journal of Theoretical and Computational Chemistry 08, no 06 (décembre 2009) : 1197–215. http://dx.doi.org/10.1142/s0219633609005416.

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The above threshold dissociation (ATD) of the HD+ molecular ion in a linearly polarized femtosecond laser field is theoretically studied using three-dimensional time-dependent quantum wave packet method. Based on the Born–Oppenheimer approximation (BOA), calculations are performed on two electronic states, the ground state 1sσ and the excited state 2pσ. The energy-dependent distributions of the dissociated fragments, resulting from the ATD, are calculated by using an asymptotic-flow expression in the momentum space. The numerical results demonstrate that, in the laser field of wavelength λ = 800 nm and full-width at half-maximum (FWHM) τ = 30 fs , only two-photon dissociation is observable at a weaker pulse peak intensity, 5.0 × 1012 W cm -2, while at an intense intensity, 1.5 × 1015 W cm -2, the dissociated fragments resulting from four-photon absorption dominates over the photodissociation process. These results are consistent with the experimental observation of Orr et al. [Orr PA et al., Phys Rev Lett98:163001, 2007]. The ac Stark-shift caused by intense laser field will change the kinetic energies of the fragments. The ATD phenomena are quantitatively interpreted in terms of the concept of light-induced potential. The molecular rotation and alignment have some effects on the kinetic energy spectrum of the dissociated fragments. The molecular rotation reduces the ac Stark-shift and broadens the peaks of kinetic energy spectra of the dissociated fragments. However, the intense laser field can effectively align the molecule and is helpful to increase the ATD probability. The ATD spectrum is related to the initial quantum numbers J0 and M0 of the molecule. The ATD spectrum of HD+ is calculated at a limited thermal temperature.
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34

Dhote, A. M., S. C. Patil, S. M. Kanetkar, S. A. Gangal et S. B. Ogale. « Metallization of glass/ceramic from solutions of organometallic compounds by laser induced pyrolysis ». Journal of Materials Research 7, no 7 (juillet 1992) : 1685–89. http://dx.doi.org/10.1557/jmr.1992.1685.

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Direct writing of iron lines on glass and Al2O3 has been achieved by CW CO2 laser-driven pyrolytic dissociation of volatile iron pentacarbonyl liquid. Since a very high organometallic molecular density is realized in the solution, use of a liquid precursor has enabled deposition of micron-thick iron films at the writing speeds of 10–400 mm s−1, which are significantly higher as compared to those achievable by the conventional CVD method. The iron stripes deposited on the glass substrate at the laser power density of 5.3 kW cm−2 and the writing speed of 100 mm s−1 are found to have a resistivity of about 580 μohm-cm. These stripes have been found to have an integral bond with the substrate due to the interface reaction.
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35

Stwalley, William C., et John T. Bahns. « Atomic, molecular, and photonic processes in laser-induced plasmas in alkali metal vapors ». Laser and Particle Beams 11, no 1 (mars 1993) : 185–204. http://dx.doi.org/10.1017/s0263034600007047.

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The production of laser-induced plasmas, which ordinarily occurs only at high laser powers, occurs at far lower laser powers using resonant and collisional phenomena in alkali metal vapors. For example, 10 torr of Na vapor can be significantly ionized to produce a bright white ball with as little as 1 mW of focused cw dye laser power (e.g., at the 3p → 4d transitions at 568.3 and 568.8 nm). We first discuss the alkali metal vapors in general (1) and their important ionization processes (2), especially those occurring at photon energies below the atomic ionization energy. We then discuss the striking wavelength dependences of ionization. For example, cw laser irradiation of these vapors gives completely different behavior at slightly different wavelengths (Stwalley 1990): 10 torr of sodium vapor at 568.2 nm, where the vapor shows only molecular fluorescence and is sufficiently quiescent that highly stable, narrow-band, optically pumped lasers based upon the fluorescent transitions can easily be constructed (Bahns 1983; Bahns et al. 1983; Verma et al. 1983); and, at 568.3 nm, where a “quasiresonant” laser-induced plasma forms and strong emission (including violet excimer bands, a potential laser) is produced (Koch & Collins 1979; Bahns et al. 1989a; Bahns et al. 1989b). We will analyze and reinterpret the classic subthreshold ionization studies (3) and survey recent laser-induced plasma studies (4). We also discuss dissociative recombination and its selectivity for producing strong excimer emission (5) the predicted electronic spectra of the alkali metal molecular ions (6).
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36

Berman, Michael R., et C. Bradley Moore. « The Small Molecule Limit of Infrared Multiphoton Dissociation : Collisional Effects in D2CO ». Laser Chemistry 8, no 2-4 (1 janvier 1988) : 169–91. http://dx.doi.org/10.1155/lc.8.169.

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The infrared multiphoton excitation of D2CO was studied by monitoring infrared fluorescence from stretching modes of D2CO following excitation in the bending modes. The dependence of the infrared multiphoton dissociation yield on laser wavelength, on laser power, and on reactant and foreign gas pressures was also studied. Severe bottlenecks to excitation through the first few steps are found. Vibration-to-vibration transfer of a bending quantum from one excited D2CO molecule to another is a crucial step. Collision-induced changes of rotational quantum number must also play an important role.
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37

Hoheisel, W., U. Schulte, M. Vollmer, R. Weidenauer et F. Tr�ger. « Dissociation of small metal particles induced by surface plasmon excitation with laser light ». Zeitschrift f�r Physik D Atoms, Molecules and Clusters 12, no 1-4 (mars 1989) : 245–47. http://dx.doi.org/10.1007/bf01426948.

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38

Bohátka, S., J. Gál, Gy Hegyesi, J. Szádai, T. Feurer et R. Sauerbrey. « Fast-pulse-mode quadrupole mass spectrometer for the detection of laser induced dissociation in molecular beams ». Vacuum 48, no 7-9 (septembre 1997) : 735–37. http://dx.doi.org/10.1016/s0042-207x(97)00039-0.

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39

Abdushelishvili, G. I., T. G. Abzianidze, A. G. Bakhtadze, P. D. Kervalishvili, G. I. Tkeshelashvili et T. B. Tzinadze. « Boron Particles Production in Nonequilibrium Laser-Chemical Radical Reactions During the IR Multiphoton Dissociation of HCIC=CBCI2H Molecules ». Laser Chemistry 10, no 2 (1 janvier 1989) : 81–92. http://dx.doi.org/10.1155/1989/73481.

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The study of IR MPD of HCIC=CBCI2H molecule by CO2.-laser is presented. We provide experimental results showing high degree of fragmentation of this molecule (down to elementary boron) during nonequilibrium laser induced radical bimolecular reactions.
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40

Simonov, A. P., G. A. Abakumov, V. T. Yaroslavtzev, V. A. Lunchev et E. A. Fedorov. « Multiple Photon High Vibrational CH Overtone Resonant and One-Photon Dissociation of Toluene Radical Cation ». Laser Chemistry 5, no 5 (1 janvier 1985) : 275–89. http://dx.doi.org/10.1155/lc.5.275.

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Photodissociation of molecular radical cations of toluenes C7H8+· (I), C6H5CD3+· (II), C7D8+· (III), cycloheptatriene C7H8+· (IV), and benzene has been studied by the method of two-pulse two-colour laser photolysis of molecules in a mass spectrometer using wavelengths 1064, 532, and 355 nm. The I ions formed due to sequential two-photon ionization of toluene molecules by the 266 nm radiation isomerize supposingly into 5-methylene-cyclohexadiene (VI). Two- and three-photon stepwise dissociation of the I and II isomers (VI and VI-d3, respectively) induced by the 1064 nm radiation has a resonance at the third overtone level of CH aliphatic bond stretching vibrations. Internal energy randomization in the two-photon dissociation is much less for VI-d3 as compared to VI. The mechanisms of isoenergetic dissociation (two- and one-photon processes induced by the 1064 and 532 nm radiations, respectively) are different: the one-photon decay via an electronically excited state proceeds considerably faster than the two-photon decomposition does in the ground state. The photodissociation cross sections have been determined. It has been shown that the intensity of CH stretching vibration overtones can be essentially higher for radical cations than for the neutral molecules.
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41

PIGLMAYER, KLAUS, MIKAEL LINDSTAM et MATS BOMAN. « PHOTON-ENHANCED SURFACE DISSOCIATION EFFECTS IN LASER PHOTOLYSIS OF AMORPHOUS CARBON FROM CH2I2 ». Surface Review and Letters 08, no 06 (décembre 2001) : 609–12. http://dx.doi.org/10.1142/s0218625x01001555.

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With near-UV Ar +-laser-induced photolysis of gaseous CH 2 I 2, efficient, large-area or localized deposition of iodine-free amorphous carbon is possible at room temperature. The method allows a separate substrate heating and thereby a tuning of the deposits properties from soft and polymer-like to diamond-like. This article reports on an observed photon–surface interaction resulting in an enhanced carbon film formation. The shape of the deposit indicates that the deposition process is supported by an increased absorption cross section of surface-adsorbed intermediate molecular fragments, with respect to flat-angle surface-impinging photons.
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42

Hübner, Göran, Catharina Crone et Buko Lindner. « Application of Sustained off-Resonance Irradiation Infrared Multiphoton Dissociation Tandem Mass Spectrometry to the Analysis of Biomolecules ». European Journal of Mass Spectrometry 11, no 5 (octobre 2005) : 483–87. http://dx.doi.org/10.1255/ejms.750.

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A modified pulse sequence for infrared multiphoton dissociation (IRMPD) experiments on a Fourier transform ion cyclotron resonance (ICR) mass spectrometer in conjunction with sidekick trapping is presented. For IRMPD tandem mass spectrometry experiments gated trapping is normally applied. It ensures that the ions remain on-axis and, thus, cross the laser beam which is aligned on-axis in commercially available instruments. Sidekick trapping is used to capture more ions in the ICR cell in order to increase the signal intensity. However, it may lead to off-axis ion motion, which reduces or even excludes interaction with the laser beam. In this contribution, sustained off-resonance irradiation (SORI) was applied to overcome this disadvantage of sidekick trapping. SORI is normally used in conjunction with collision-induced dissociation experiments to increase the kinetic energy of the ions. Here, SORI is used to influence the cyclotron motion during the laser irradiation time, which leads to a temporary intersection of the ion trajectory with the laser beam. With this easy-to-handle experimental set-up, IRMPD of ions captured with sidekick trapping again leads to the generation of fragment ions, as is demonstrated with several biologically relevant samples like peptides, lipids and glycolipids.
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43

Telle, H. H. « Stimulated Processes in a Half-collision ». Laser Chemistry 5, no 6 (1 janvier 1986) : 393–406. http://dx.doi.org/10.1155/lc.5.393.

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Selective photodissociation of diatomic molecules is used to prepare the separating species in a well defined quantum state with narrowly determined final kinetic energy of the particles. During the course of separation to products the repulsive potential is probed by a tunable dye laser, that is by induced absorption in case the dissociation proceeds on a potential leading to ground state products, or by induced emission or absorption for all other cases. The determination of interatomic potentials from the observed spectra is discussed.
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44

Skordoulis, C., E. Sarantopoulou, S. M. Spyrou, C. Kosmidis et A. C. Cefalas. « Laser induced fluorescence (LIF) of Hg2 and Hg3 via dissociation of HgBr2 at 157 nm ». Zeitschrift f�r Physik D Atoms, Molecules and Clusters 18, no 2 (juin 1991) : 175–80. http://dx.doi.org/10.1007/bf01437444.

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45

Wang, Pengqian, A. Max Sayler, Kevin D. Carnes, Brett D. Esry et Itzik Ben-Itzhak. « Disentangling the volume effect through intensity-difference spectra: ? application to laser-induced dissociation of H2+ ». Optics Letters 30, no 6 (15 mars 2005) : 664. http://dx.doi.org/10.1364/ol.30.000664.

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46

Chen, Hao, Li Sun, Gang Li, Shu Yi Zhang et Hui Lan Chen. « Laser-induced time-resolved photoacoustic calorimetry study on photo-dissociation of human and bovine oxyhemoglobin ». Biochemical and Biophysical Research Communications 319, no 1 (juin 2004) : 157–62. http://dx.doi.org/10.1016/j.bbrc.2004.04.166.

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47

Petin, A. N., et G. N. Makarov. « Infrared laser-induced isotope-selective dissociation of mixed (CF3Br) mArn van der Waals clusters ». Quantum Electronics 49, no 6 (17 juin 2019) : 593–99. http://dx.doi.org/10.1070/qel16912.

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48

Yamanouchi, Kaoru, et Robert W. Field. « Short Time Dynamics of Highly Excited Small Polyatomic Molecules Extracted From Laser Spectra ». Laser Chemistry 16, no 1 (1 janvier 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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49

Sayler, A. M., P. Q. Wang, K. D. Carnes et I. Ben-Itzhak. « Determining intensity dependence of ultrashort laser processes through focusz-scanning intensity-difference spectra : application to laser-induced dissociation of H+2 ». Journal of Physics B : Atomic, Molecular and Optical Physics 40, no 22 (30 octobre 2007) : 4367–78. http://dx.doi.org/10.1088/0953-4075/40/22/006.

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50

Borbély, Adina, Lilla Pethő, Ildikó Szabó, Mohammed Al-Majidi, Arnold Steckel, Tibor Nagy, Sándor Kéki et al. « Structural Characterization of Daunomycin-Peptide Conjugates by Various Tandem Mass Spectrometric Techniques ». International Journal of Molecular Sciences 22, no 4 (6 février 2021) : 1648. http://dx.doi.org/10.3390/ijms22041648.

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The use of peptide-drug conjugates has generated wide interest as targeted antitumor therapeutics. The anthracycline antibiotic, daunomycin, is a widely used anticancer agent and it is often conjugated to different tumor homing peptides. However, comprehensive analytical characterization of these conjugates via tandem mass spectrometry (MS/MS) is challenging due to the lability of the O-glycosidic bond and the appearance of MS/MS fragment ions with little structural information. Therefore, we aimed to investigate the optimal fragmentation conditions that suppress the prevalent dissociation of the anthracycline drug and provide good sequence coverage. In this study, we comprehensively compared the performance of common fragmentation techniques, such as higher energy collisional dissociation (HCD), electron transfer dissociation (ETD), electron-transfer higher energy collisional dissociation (EThcD) and matrix-assisted laser desorption/ionization–tandem time-of-flight (MALDI-TOF/TOF) activation methods for the structural identification of synthetic daunomycin-peptide conjugates by high-resolution tandem mass spectrometry. Our results showed that peptide backbone fragmentation was inhibited by applying electron-based dissociation methods to conjugates, most possibly due to the “electron predator” effect of the daunomycin. We found that efficient HCD fragmentation was largely influenced by several factors, such as amino acid sequences, charge states and HCD energy. High energy HCD and MALDI-TOF/TOF combined with collision induced dissociation (CID) mode are the methods of choice to unambiguously assign the sequence, localize different conjugation sites and differentiate conjugate isomers.
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