Theoretical studies of the reactions H + CH [yields] C + H[sub 2] and C + H[sub 2] [yields] CH[sub 2] using an ab ini global ground-state potential surface for CH[sub 2]
- Argonne National Lab., IL (United States)
- Northwestern Univ., Evanston, IL (United States)
Ab initio, multireference, configuration interaction (CI) calculations have been used to characterize the ground-state potential surface of methylene. The calculations employ a full-valence complete-active-space reference wave function and a (4s,3p,2d,If/3s,2p,1d) basis set. The calculations were carried out at approximately 6000 points, and the resulting energies were fit to a many-body expansion including conical intersections between the [sup 3]B[sub 1] and [sup 3]A[sub 2] states for C[sub 2v] geometries and between the [sup 3]II and [sup 3][Sigma][sup [minus]] states for linear geometries. The calculations show that the C[sub 2v] conical intersection provides a zero barrier route for the C([sup 3]P) + H[sub 2] insertion reaction. Quasiclassical trajectory studies of the title reactions using the global surface indicate that both reactions proceed without activation energy and that the thermal rate constants are nearly independent of temperature. The rate constants for H + CH agree with high-temperature (2000 K) experimental studies but are substantially higher (factor of 10) than a measurement at 297 K. For C + H[sub 2], the CH[sub 2] lifetimes at thermal energies are approximately 20 ps which is in agreement with an experimentally derived estimate. 21 refs., 14 figs., 6 tabs.
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 6232020
- Journal Information:
- Journal of Physical Chemistry; (United States), Vol. 97:21; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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