Infrared spectroscopy of entrance channel complexes

David T. Anderson; Rebecca L. Schwartz; Michael W. Todd; Jeanne M. Hossenlopp; Marsha I. Lester

doi:10.1117/12.308405

15 May 1998 Infrared spectroscopy of entrance channel complexes

David T. Anderson, Rebecca L. Schwartz, Michael W. Todd, Jeanne M. Hossenlopp, Marsha I. Lester

Proceedings Volume 3271, Laser Techniques for State-Selected and State-to-State Chemistry IV; (1998) https://doi.org/10.1117/12.308405
Event: Optoelectronics and High-Power Lasers and Applications, 1998, San Jose, CA, United States

Abstract

The entrance channel to the OH + H₂ yields H₂O + H hydrogen abstraction reaction has been probed with unprecedented detail through IR overtone spectroscopy of binary OH-H₂/D₂ complexes. IR-UV double resonance techniques have been used to obtain rotationally resolved vibrational overtone spectra for ortho-H₂-OH as well as ortho- and para-D₂OH. Assignment of the spectra has been aided by bound state calculations based on the ab initio potential of Clary, Werner, and coworkers. The pure overtone stretch and combination bands involving intermolecular bending vibrations at energies up to the OH(v equals 2) + H₂/D₂ dissociation limit have been observed. The intermolecular excitations can drastically alter the relative orientation of the reactants within the complex, producing some that resemble the transition state structure. Direct time-domain measurements show that vibrationally activated OH-H₂ complexes have a lifetime of 115(13) ns for the pure overtone stretch and an upper limit of 5 ns for OH-D₂. The 20 times faster decay for OH-D₂ arises form near-resonant vibrational energy transfer from OH to D₂. Finally, IR optical pumping provides sufficient population transfer to enable the rotational distribution of the OH(v equals 1) products from inelastic scattering to be determined.

Citation Download Citation

David T. Anderson, Rebecca L. Schwartz, Michael W. Todd, Jeanne M. Hossenlopp, and Marsha I. Lester "Infrared spectroscopy of entrance channel complexes", Proc. SPIE 3271, Laser Techniques for State-Selected and State-to-State Chemistry IV, (15 May 1998); https://doi.org/10.1117/12.308405

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