Nonadiabatic quantum dynamics of C( 1 D )+H 2 →CH+H: Coupled-channel calculations including Renner-Teller and Coriolis terms

The Renner-Teller (RT) coupled-channel dynamics for the ${\rm C}( {{}^1D} )+{\rm H}_{\rm 2} ( {X{}^{\rm 1}{\rm \Sigma }_g^ + } ) \to {\rm CH}( {X^2 \Pi } )\break + {\rm H}( {{}^2S} )$ C ( D 1 ) + H 2 ( X Σ g + 1 ) → CH ( X 2 Π ) + H ( S 2 ) reaction has been investigated for the first time, considering the first two singlet states $\tilde a{}^1A^{\rm \prime }$ a ̃ 1 A ′ and $\tilde b{}^1A^{\prime \prime }$ b ̃ 1 A ′ ′ of CH 2 dissociating into the products and RT couplings, evaluated through the ab initio matrix elements of the electronic angular momentum. We have obtained initial-state-resolved probabilities, cross sections and thermal rate constants via the real wavepacket method for both coupled electronic states. In contrast to the ${\rm N}( {{}^2D} ) + {\rm H}_{\rm 2} ( {X{}^{\rm 1}{\rm \Sigma }_g^ + } )$ N ( D 2 ) + H 2 ( X Σ g + 1 ) system, RT effects tend to reduce probabilities, cross sections, and rate constants in the low energy range compared to Born-Oppenheimer (BO) ones, due to the presence of a repulsive RT barrier in the effective potentials and to long-lived resonances. Furthermore, contrary to BO results, the rate constants have a positive temperature dependence in the 100-400 K range. The two-state RT rate constant at 300 K, lower than the BO one, remains inside the error bars of the experimental value.