Institut UTINAM - UMR 6213 - Renner-Teller quantum theory of atom+diatom collisions

Résumé : A quantum theory of Renner-Teller (RT) effects in atom+diatom collisions is presented, beyond the Born-Oppenheimer (BO) approximation. Starting form a previous general theory of nonadiabatic effects in triatoms, two embeddings of the body-fixed frame are briefly discussed, a symmetry-adapted rovibronic representation is defined, and Hamiltonian matrix elements are obtained, taking into account two RT-interacting electronic states and Coriolis couplings (CC).
This formalism is applied to the reactions $N(^2D)+H_2(\tilde X^1 \Sigma^+_g) \to NH(\tilde X^3 \Sigma^-)+H(^2S)$ , $NH(\tilde a^1 \Delta)+H’(^2S) \to N(^2D)+H_2(\tilde X^1 \Sigma^+_g)$ , and $NH(\tilde a^1 \Delta)+H’(^2S)\to NH’(\tilde a^1 \Delta)+H(^2S)$ , using recent and accurate $NH_2$ $\tilde X^2 B_1$ and $\tilde A^2 A_1$ potential energy surfaces. The first reaction is investigated at the RT-CC level, presenting
collision observables averaged over initial degenerate electronic and spin-nuclear states, and comparing BO
and RT results. The second and third collisions are investigated and contrasted within the BO approximation,
and some preliminary RT results are also reported. CCs are finally discussed in all reactions.

Institut UTINAM - UMR 6213

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Renner-Teller quantum theory of atom+diatom collisions