## Abstract

Ab initio, multireference, configuration interaction (CI) calculations have been used to characterize the groundstate potential surface of methylene. The calculations employ a full-valence, complete-active-space reference wave function and a (4s,3p,2d,1f/3s,2p,1d) basis set. The calculations were carried out at ∼6000 points, and the resulting energies were fit to a many-body expansion including conical intersections between the ^{3}B_{1} and ^{3}A_{2} states for C_{2v} geometries and between the ^{3}II and ^{3}Σ^{-} states for linear geometries. The calculations show that the C_{2v} conical intersection provides a zero barrier route for the C(^{3}P) + H_{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_{2}, the CH_{2} lifetimes at thermal energies are approximately 20 ps which is in agreement with an experimentally derived estimate.

Original language | English |
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Pages (from-to) | 5472-5481 |

Number of pages | 10 |

Journal | Journal of Physical Chemistry |

Volume | 97 |

Issue number | 21 |

Publication status | Published - 1993 |

## ASJC Scopus subject areas

- Physical and Theoretical Chemistry