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Bechtel HA, Camden JP, Brown DJ, et al. Comparing the dynamical effects of symmetric and antisymmetric stretch excitation of methane in the Cl+CH4 reaction. J Chem Phys. 2004;120(11):5096-103doi: 10.1063/1.1647533.
Bechtel, H. A., Camden, J. P., Brown, D. J., & Zare, R. N. (2004). Comparing the dynamical effects of symmetric and antisymmetric stretch excitation of methane in the Cl+CH4 reaction. The Journal of chemical physics, 120(11), 5096-103. https://doi.org/10.1063/1.1647533
Bechtel, Hans A, et al. "Comparing the dynamical effects of symmetric and antisymmetric stretch excitation of methane in the Cl+CH4 reaction." The Journal of chemical physics vol. 120,11 (2004): 5096-103. doi: https://doi.org/10.1063/1.1647533
Bechtel HA, Camden JP, Brown DJ, Zare RN. Comparing the dynamical effects of symmetric and antisymmetric stretch excitation of methane in the Cl+CH4 reaction. J Chem Phys. 2004 Mar 15;120(11):5096-103. doi: 10.1063/1.1647533. PMID: 15267378.
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J Chem Phys. 2004 Mar 15;120(11):5096-103. doi: 10.1063/1.1647533.

Comparing the dynamical effects of symmetric and antisymmetric stretch excitation of methane in the Cl+CH4 reaction.

The Journal of chemical physics

Hans A Bechtel, Jon P Camden, Davida J Ankeny Brown, Richard N Zare

Affiliations

  1. Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.

PMID: 15267378 DOI: 10.1063/1.1647533

Abstract

The effects of two nearly isoenergetic C-H stretching motions on the gas-phase reaction of atomic chlorine with methane are examined. First, a 1:4:9 mixture of Cl(2), CH(4), and He is coexpanded into a vacuum chamber. Then, either the antisymmetric stretch (nu(3)=3019 cm(-1)) of CH(4) is prepared by direct infrared absorption or the infrared-inactive symmetric stretch (nu(1)=2917 cm(-1)) of CH(4) is prepared by stimulated Raman pumping. Photolysis of Cl(2) at 355 nm generates fast Cl atoms that initiate the reaction with a collision energy of 1290+/-175 cm(-1) (0.16+/-0.02 eV). Finally, the nascent HCl or CH(3) products are detected state-specifically via resonance enhanced multiphoton ionization and separated by mass in a time-of-flight spectrometer. We find that the rovibrational distributions and state-selected differential cross sections of the HCl and CH(3) products from the two vibrationally excited reactions are nearly indistinguishable. Although Yoon et al. [J. Chem. Phys. 119, 9568 (2003)] report that the reactivities of these two different types of vibrational excitation are quite different, the present results indicate that the reactions of symmetric-stretch excited or antisymmetric-stretch excited methane with atomic chlorine follow closely related product pathways. Approximately 37% of the reaction products are formed in HCl(v=1,J) states with little rotational excitation. At low J states these products are sharply forward scattered, but become almost equally forward and backward scattered at higher J states. The remaining reaction products are formed in HCl(v=0,J) and have more rotational excitation. The HCl(v=0,J) products are predominantly back and side scattered. Measurements of the CH(3) products indicate production of a non-negligible amount of umbrella bend excited methyl radicals primarily in coincidence with the HCl(v=0,J) products. The data are consistent with a model in which the impact parameter governs the scattering dynamics.

(c) 2004 American Institute of Physics.

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