Electronically non-adiabatic transitions in high-energy CH₃I + CH₃I collisions computed by the quantal FMS method using the Evans-Polanyi potential

The effective energy threshold for the crossing into an electronically excited state and the post threshold rise of the yield of crossing are discussed. The time-dependent Schrödinger equation for multiple electronic states is solved using the full multiple spawning (FMS) methodology. The quantal results are compared with classical path methods. The potential energy function is of the LEP form including the electronically excited surface. For kinematic reasons, the yield is exponentially small until an effective threshold, at ∼ 10 km s^-1, with a steep rise of the yield in the post threshold regime.