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3. Effects of solvation by a single atom on photodissociation: Classical and quantum/classical studies of HCl photolysis in Ar···HCl.

Author

García-Vela, A., Gerber, R. B., and Valentini, J. J.

Subjects
HYDROCHLORIC acid, PHOTOCHEMISTRY, SOLVATION, PHOTODISSOCIATION
Abstract

The photolysis of HCl in the cluster Ar···HCl is studied theoretically with the objective of elaborating on the effect of a single ‘‘solvent’’ atom on the dynamics of chemical bond breaking. The focus is on observable properties, such as the velocity distribution and the angular distribution of the H atom product, on how these properties reflect the ‘‘solvent’’ effect, and on the physical mechanisms involved. The main results obtained are the following. (1) There is a high probability for at least a single ‘‘hard’’ collision between the H photofragment and the Ar atom before the H atom leaves the cluster. Multiple collisions between the H and the heavy atoms also occur with significant probability. (2) The final kinetic-energy distribution of the H atom shows a long pronounced tail due to energy transfer in the collisions with the heavy atoms. (3) There are pronounced peaks in the angular distribution of the H atom due to the single and multiple collision events. (4) Comparison of photolysis of Ar···HCl with that of Ar···DCl shows a large isotope effect, again due to collisions within the cluster during its fragmentation. The results were mostly obtained from classical trajectory calculations, but also in part from calculations using a hybrid quantum/classical method in which the H atom is treated by quantum wave packets while the heavy atoms are described classically. The quantitative results show some quantum effects, but for most purposes the classical description is sustained. Implications of the results for experimental studies of molecular photodissociation in clusters are discussed. [ABSTRACT FROM AUTHOR]

Published
1992

4. Vibrational states and structure of Ar3: The role of three-body forces.

Author

Horn, T. R., Gerber, R. B., Valentini, J. J., and Ratner, M. A.

Subjects
EIGENFUNCTIONS, SELF-consistent field theory, VIBRATIONAL spectra
Abstract

Vibrational energies and eigenfunctions of Ar3, including some pertaining to highly excited states, are computed, and insights into their dynamical and structural properties are obtained. The method used employs the vibrational self-consistent-field (SCF) theory in hyperspherical coordinates as a first approximation. Exact results are obtained by configuration interaction, using the SCF states as an efficient basis. A focal point of the study is the effect of three-body potentials on the vibrational spectrum. Axilrod–Teller and other three-body potentials are used to examine this. It is found that the effect of three-body forces on the spectrum is substantial, and larger than effects due to uncertainties in the presently known two-body Ar–Ar potentials. This suggests that experimental spectroscopy of Ar3 may be used to determine reliable three-body forces among Ar atoms. It is also shown that the three-body double-dipole–quadrupole interaction, while less important than the Axilrod–Teller one, has a significant effect on the vibrational spectrum. Finally, a detailed analysis is made of the Ar–Ar distance distributions in the various states, of the structural distributions of Ar3, and of the properties of the wave functions. We find that the wave functions show well-ordered nodal patterns even for the highly excited large-amplitude states. Thus, these states do not correspond qualitatively to ‘‘liquid-like’’ behavior of the cluster. [ABSTRACT FROM AUTHOR]

Published
1991
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9. Laser chemical physics III

Author

Goldberg, S., Moore, D. S., Bomse, David S., Valentini, J. J., Beckmann, A., Baierl, P., Fietz, H., Kiefer, W., Attal, B., Müller-Dethlefs, K., Débarre, D., Taran, J. -P., Ernst, W. E., Törring, T., Sumida, D., Wittig, C., Stuke, M., Abakumov, G. A., Manveljan, R. V., Polyakov, B. I., Simonov, A. P., Yaroslavtzev, V. T., Mashni, m., Hess, P., Graf, H. P., Kneubuehl, F. K., Siomos, K., Christophorou, L. G., Schell-Sorokin, A. J., Lankard, J. R., Bethune, D. S., Loy, M. M. T., Sorokin, P. P., and Wessel, J.

Published
1982
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19. General discussion

Author

Polanyi, J. C., primary, Neumark, D. M., additional, Schatz, G., additional, Truhlar, D. G., additional, Valentini, J. J., additional, Taylor, H., additional, Balint-Kurti, G. G., additional, Manolopoulos, D. E., additional, Child, M. S., additional, Manz, J., additional, Kubach, C., additional, Bowman, J. M., additional, Laganà, A., additional, Aguilar, A., additional, Gimenez, X., additional, Lucas, J. M., additional, Dixon, R. N., additional, Simons, J. P., additional, Schinke, R., additional, Hancock, G., additional, Gericke, K. H., additional, Ashfold, M. N. R., additional, Schnieder, L., additional, Welge, K. H., additional, Hippler, M., additional, Pfab, J., additional, Janza, A. E., additional, Karrlein, W., additional, Morokuma, K., additional, Alexander, M. H., additional, Metiu, H., additional, Yamashita, K., additional, Temps, F., additional, Simpson, A. W., additional, Brouard, M., additional, Wang, J.-X., additional, Henchman, M., additional, Katz, B., additional, Casavecchia, P., additional, Balucani, N., additional, Beneventi, L., additional, Stranges, D., additional, Volpi, G. G., additional, Whitehead, J. C., additional, Wei-Keh Wu, V., additional, Orr-Ewing, A. J., additional, Whitaker, B., additional, Frey, J. G., additional, Shapiro, M., additional, Rubahn, H.-G., additional, Murrell, J. N., additional, Stwalley, W. C., additional, Grice, R., additional, Girard, B., additional, Billy, N., additional, Gouédard, G., additional, Vigué, J., additional, Werner, H.-J., additional, McCaffery, A. J., additional, Levy, M. R., additional, and Burnett, K., additional

Published
1991
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20. General discussion

Author

Smith, I. W. M., primary, Valentini, J. J., additional, Neumark, D. M., additional, Ashfold, M. N. R., additional, González, M., additional, Temps, F., additional, Laganà, A., additional, Alvariño, J. M., additional, Quintales, L. M., additional, Polanyi, J. C., additional, Grice, R., additional, Truhlar, D. G., additional, McKendrick, K. G., additional, Aoiz, F. J., additional, Mackay, R. S., additional, Xu, Q.-X., additional, Wu, V. W.-K., additional, Clary, D. C., additional, Soep, B., additional, Schatz, G., additional, Child, M. S., additional, Shapiro, M., additional, Zewail, A. H., additional, Metiu, H., additional, Plane, J. M. C., additional, Gerber, G., additional, Combariza, J. E., additional, Manz, J., additional, Paramonov, G. K., additional, Görtler, S., additional, Simons, J. P., additional, Morokuma, K., additional, Kolba, E., additional, Kosloff, R., additional, Sondermann, F., additional, Herrero, V. J., additional, Rábanos, V. Sáez, additional, Welge, K. H., additional, Girard, B., additional, Manolopoulos, D. E., additional, Casavecchia, P., additional, Balucani, N., additional, Beneventi, L., additional, Stranges, D., additional, Volpi, G. G., additional, Bowman, J. M., additional, Marcus, R. A., additional, Pack, R. T., additional, Parker, G. A., additional, Connor, J. N. L., additional, Chatfield, D. C., additional, Friedman, R. S., additional, Lynch, Ms. G. C., additional, Foster, R., additional, Frost, M. J., additional, Hippler, H., additional, Schlepegrell, A., additional, Troe, J., additional, Gericke, K.-H., additional, Alexander, M. H., additional, Dagdigian, P. J., additional, Clement, S. G., additional, Howe, J. D., additional, Western, C. M., additional, Dixon, R. N., additional, and Sarre, P. J., additional

Published
1991
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21. General discussion

Author

Hodgson, A., primary, Hayden, B. E., additional, Truhlar, D. G., additional, Randall, R., additional, Truong, T., additional, Kleyn, A. W., additional, Manz, J., additional, Alexander, M. H., additional, Holloway, S., additional, Murrell, J. N., additional, Buckingham, A. D., additional, Ceyer, S. T., additional, Valentini, J. J., additional, Shapiro, M., additional, Ardebili, M. H. P., additional, Hughes, C. J., additional, Whitehead, J. C., additional, Grice, R., additional, Chesters, M. A., additional, Polanyi, J. C., additional, Marcus, R. A., additional, Metiu, H., additional, and Zewail, A. H., additional

Published
1991
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22. Mapping Reaction Dynamics via State-to-State Measurements:  Rotations Tell the Tale

Author

Valentini, J. J.

Abstract

We describe a series of experiments and computational simulations of the state-to-state dynamics of the atom transfer reactions H + HX → H2(v‘,j‘) + X (HX = hydrogen halide) and H + RH → H2(v‘,j‘) + R (RH = alkane). The rotational and vibrational state distributions of the H2 products are characterized for reaction at well-defined initial conditions. The vibrational state distributions provide some information. However, it is the rotational state distributions that form the basis for mapping the path from reactants to products. In analyzing these state distributions, we develop a method that takes explicit, quantitative account of kinematic constraints on the product energy disposal. This method is generally applicable to bimolecular reactions and provides a context in which to interpret the rotational and vibrational state distributions.

Published
2002
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24. Resonance Raman Studies of Photoinduced Decomposition of Nylon-6,6:  Product Identification and Mechanistic Determination

Author

Matsui, H., Arrivo, S. M., Valentini, J. J., and Weber, J. N.

Abstract

We report observation of an enal product of the decomposition of both nylon-6,6 and a nylon-6,6 model compound, N,N-hexamethylenebis(hexamide), upon 266 nm pulsed UV laser irradiation of these amides. The product is identified by UV resonance Raman spectroscopy, which shows characteristic band frequencies and intensities of the C&dbd;C and C&dbd;O stretches of the enal. The vibrational assignment and product identification are supported by experiments with 15N-labeled nylon-6,6. Degradation and spectroscopic characterization under 16O2, 18O2, and N2 show that the degradation channel leading to the enal requires molecular oxygen and thereby indicate an oxidative mechanism. The product resonance Raman intensities are directly proportional to the number of photons incident on the sample, consistent with a direct photooxidative process, rather than a thermal−oxidative one with the laser serving as a heat source. We do not observe the enal product when the nylon-6,6 or model compound are simply heated in oxygen-containing atmospheres, except when the heating produces melting.

Published
2000

25. Dynamics of 14N16O and 15N18O excited with an ArF-exciplex laser at 193 nm

Author

Hack, W., Sander, R. K., Valentini, J. J., and Nogar, N. S.

Abstract

The dynamics of the B2∏r(ν' = 7) state of 14N16O and the heavy-heavy molecular isotope 15N18O was studied in a laser induced fluorescence bulb system at room temperature. The NO was excited at 193 nm with an exciplex laser. The fluorescence was observed spectrally and time resolved. The NO pressure was varied in the range 10 ˇ- p(15N 18O)/Pa ˇ- 140. Quenching gases He, Ar, Xe, and N2 were added from 13 Pa up to about 90·0 kPa. For 15N18O the collision-free radiative lifetime was determined to be τo(NO) = 0·38 ± 0·05 μs and the self-quenching rate was found to be kQ(NO) = (1·7 ± 0·2) × 1014 cm3 mol-1 s-1. A significant difference with the 14N16O isotope was not found. Quenching rates for Ar and N2 are determined to be kQ(Ar) = (4·3 ± 1·5) × 1013 cm3 mol-1 s-1 and kQ(N2) = (7·9 + 2·0) × 1013 cm3 mol-1 s-1. The quenching mechanism is discussed.

Published
1985
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27. State-to-State Dynamics of the H + CDCl<INF>3</INF>(v<INF>1</INF>‘‘=1) → HD(v‘,j‘) + CCl<INF>3</INF> Reaction

Author

Lanzisera, D. V. and Valentini, J. J.

Abstract

We report a study of the reaction dynamics of the H + CDCl3 → HD(v‘,j‘) + CCl3 reaction with the CDCl3 reactant prepared in the ν1 C−D stretch v‘‘=1 excited state. Stimulated Raman excitation is used to prepare the CDCl3(v‘‘=1) reactant and coherent anti-Stokes Raman scattering is used to detect the HD(v‘,j‘) product, under effectively single-collision conditions at a relative energy of 1.6 eV. Even though the vibrational excitation energy of the reactant (0.28 eV) is small compared to the collision energy, which greatly exceeds the reaction barrier height, the vibrational excitation of the reactant increases the reaction cross section by a factor of 1.66 ± 0.15. Despite this, none of the energy added by the reactant vibrational excitation appears as HD product vibration or rotation. All of it goes into product translation and/or CCl3 internal energy.

Published
1997

41. State-to-state chemical reaction dynamics in polyatomic systems: case studies.

Author

Valentini JJ

Abstract

This review illustrates the experimental study of chemical reaction dynamics using methods that select the quantum states and energy of the reactants and determine the quantum states and energy of the products. The focus is reaction dynamics in systems in which at least one of the reactants or products is a polyatomic molecule. The approach taken is to select four prototype reaction systems as case studies to demonstrate the detail of information and insight that can come from such experiments. Thus, the review is selective and neither claims nor attempts to be comprehensive. Reference to and discussion of theoretical reaction dynamics are included where computational results directly connect with the experiments.

Published
2001
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