Fragmentation and cis–trans isomerization of diimide in fs laser-pulses

The dynamics of diimide (N2H2) under excitation of femto-second laser pulses is investigated using nonadiabatic quantum molecular dynamics (NA-QMD). Distinct fragmentation channels are observed in particular by varying the laser frequency. It is found that the dynamics on the first excited state surface S1 is dominated by cis–trans isomerization with a characteristic time scale of about τ ≈ 25 fs almost independent of the nuclear initial conditions. The long time behaviour of the electronic dynamics is classified into three categories: (1) persistence on the ground state surface, (2) persistence on the first excited state surface and (3) nonadiabatic switching between both surfaces.