Interference effects in molecular system with curve crossing

The time-dependent behavior of molecular systems exhibiting a curve-crossing (either natural or photon-induced) is shown to exhibit marked interference patterns. These are particularly evident for single-mode harmonic systems and for weak inter-electronic coupling. It is shown that, in the case of degenerate potential energy surfaces, interference gives rise to jumps in the transition probability (at each passage of the wavepacket through the crossing region) whose height depends on time. In the case of non-degenerate potential energy curves, depending on the energy gap, one may observe a periodic or quasi-periodic behavior. Including additional modes results in a decrease of interferential features.