Reaction dynamics of prototypical, D + H₂ and Cl (²P) + H₂, chemical reactions occurring through the conical intersections of the respective coupled multi-sheeted potential energy surfaces is examined here. In addition to the electronic coupling, nonadiabatic effects due to relativistic spin-orbit coupling are also considered for the latter reaction. A time-dependent wave packet propagation approach is undertaken and the quantum dynamical observables viz., energy resolved reaction probabilities, integral reaction cross-sections and thermal rate constants are reported.

The effect of coriolis coupling on the dynamics of H + H₂ reaction is examined by calculating the initial state-selected and energy resolved reaction probabilities on the coupled manifold of its degenerate $2p$ ($E'$) ground electronic state. H₃ in this state is prone to the Jahn-Teller (JT) instability and consequently the degeneracy is split upon distortion from its $D_{3h}$ equilibrium geometry. The orbital degeneracy is, however, restored along the $D_{3h}$ symmetry configuration and it results into conical intersections of the two JT split component states. The energetically lower adiabatic component of latter is repulsive, and mainly (`rather solely’) drive the H + H₂ reaction dynamics. On the otherhand, the upper adiabatic component is of bound type and can only impart non-adiabaticity on the dynamics of lower state. Comparison calculations are therefore also carried out on the uncoupled lower adiabatic sheet to assess the nonadiabatic effect. Exact quantum scattering calculations are performed by a chebyshev polynomial propagator and employing the double many body expansion potential energy surface of the electronic ground state of H₃. Reaction probabilities are reported up to a total energy of ∼ 3.0 eV, slightly above the energetic minimum of the seam of conical intersections at ∼ 2.74 eV. Reaction probabilities are calculated up to the total angular momentum, $J = 20$ and for each value of 𝐽, the projection quantum number 𝐾 is varied from 0 to min ($J, K_{\text{max}}$), with $K_{\text{max}} = 4$. Probability results are compared and discussed with those obtained without the coriolis coupling.