| Autor: |
Debarre, D., Lefebvre, M., Péalat, M., Taran, J.-P. E., Bamford, D. J., Moore, C. B. |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 11/1/1985, Vol. 83 Issue 9, p4476, 12p |
| Abstrakt: |
Coherent anti-Stokes Raman Scattering (CARS) is used to monitor the rovibrational population distribution of prompt H2 produced from H2CO+hν→H2+CO. Photolysis is performed on K=1 lines of the 2141 S1←S0 transition. Scanning CARS spectroscopy is employed, with suppression of the nonresonant background of the H2CO. The detection sensitivity is ∼1012 cm-3 per quantum state. Helium buffer is added to cool the product translation to near room temperature. States v=0–4, J=1–9 are detected. The vibrational distribution peaks at v=1. The rotational distributions in the vibrational states are somewhat Boltzmann with ‘‘temperatures’’ ranging from 1700 to 2500 K for v=3–0. The total energy, 29 500 cm-1, is chosen near the threshold for dissociation. The internal energy of H2(v, J) sums with that found earlier for CO(v, J) and for translation to this total. An average impact parameter of 0.9 Å with a spread of a few tenths Å is found. H2 pushes away from a point about 0.3 Å beyond the C nucleus of CO. The distributions are controlled by the dynamics of the fragments as they separate in the steep, repulsive exit valley of the potential energy surface; they are entirely different from the statistical distributions typical for bond fission without a barrier. Rotational relaxation of H2 in collisions with He occurs at 300 K with a rate constant of (9±3)×10-13 cm3 molecule-1 s-1 for J=3→J=1 and (2.6±1)×10-13 cm3 molecule-1 s-1 for J=5→J=3. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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