Pulse-train photoelectron spectroscopy of electronic and nuclear dynamics in molecules.

We theoretically study the application of a femtosecond pulse train to simultaneously probe the electronic excitation dynamics and nuclear vibrational motion in the excited-state LiH molecule by means of time-resolved photoelectron spectroscopy. The step-like population transfers caused by continual interaction with a sequence of pulses and refractory periods are shown to give rise to time evolution of the photoelectron kinetic energy distribution as the history of molecular electronic and vibrational states. Such a signal should lead to a novel and direct way to investigate electronic and nuclear simultaneous dynamics involving multiple excited states.