On the stability of hole states in molecules and clusters

Recent investigations of the electron dynamics of molecules after irradiation with a short, strong XUV pulse have shown that under certain conditions, a rather clean deep hole state can be generated which, in turn, leads to a remarkable dipole instability. Here we analyze in more depth the dipole instability, simplifying the excitation mechanism by instantaneous generation of a hole in one of the occupied states of the system. We investigate how the dipole instability depends on the system, the state in which the hole is cut, and the amount of depletion which is given to the hole state. We also quickly discuss the mechanism beyond the dipole instability in analogy to the generation of a coherent photon field in a laser.