## Abstract

We report and compare two sets of thermal rate constants for the collinear reaction Cl + HBr → HCl + Br, which is dominated by the n = 0 vibrational state of reactants and the n = 2 vibrational state of products. One set is based on converged multichannel quantal calculations carried out using hyperspherical coordinates. The other set is based on variational transition state theory (VTST) with a least-action (LA) ground-state (G) transmission coefficient (VTST/LAG). The two sets of rate constants agree within a factor of 2.2 over the whole factor-of-12 temperature range (200-2400 K) studied. The error is comparable to what was found previously for the symmetric reaction Cl + HCl′ → HCl + Cl′, which is dominated by n = 0 states of reactants and products. This indicates that the VTST/LAG method is as applicable to reactions that proceed by tunneling into excited states as it is for ground-state-to-ground-state tunneling reactions. We also show that the VTST/LA approximation provides useful accuracy for the rate constant of the collinear excited-state reaction Cl + HBr(n = 1) → HCl + Br.

Original language | English (US) |
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Pages (from-to) | 2252-2258 |

Number of pages | 7 |

Journal | The Journal of chemical physics |

Volume | 83 |

Issue number | 5 |

DOIs | |

State | Published - 1985 |