Theoretical investigation of intersystem crossing between the a{sup ~1}A{sub 1} and Χ{sup ~3}B{sub 1} states of CH{sub 2} induced by collisions with helium
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021 (United States)
Collisional energy transfer between the ground (Χ{sup ~3}B{sub 1}) and first excited (a{sup ~1}A{sub 1}) states of CH{sub 2} is facilitated by strong mixing of the rare pairs of accidentally degenerate rotational levels in the ground vibrational manifold of the a{sup ~} state and the (020) and (030) excited bending vibrational manifolds of the X{sup ~} state. The simplest model for this process involves coherent mixing of the scattering T-matrix elements associated with collisional transitions within the unmixed a{sup ~} and X{sup ~} states. From previous calculations in our group, we have determined cross sections and room-temperature rate constants for intersystem crossing of CH{sub 2} by collision with He. These are used in simulations of the time dependence of the energy flow, both within and between the X{sup ~} and a{sup ~} vibronic manifolds. Relaxation proceeds through three steps: (a) rapid equilibration of the two mixed-pair levels, (b) fast relaxation within the a{sup ~} state, and (c) slower relaxation among the levels of the X{sup ~} state. Collisional transfer between the fine-structure levels of the triplet (X{sup ~}) state is very slow.
- OSTI ID:
- 22420029
- Journal Information:
- Journal of Chemical Physics, Vol. 141, Issue 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
Similar Records
Relaxation and reaction of HCO and CH/sub 2/(/sup 1/A/sub 1/)
Energy transfer in the /sup 1/A/sub u/ state of glyoxal. III. Deuterium effects