Attosecond Dynamics of Coherent Electron–Nuclear Wave Packets in Molecules

Abstract

The natural time scale of electron motion in atoms is the attosecond (10−18 s). In molecules, this time scale becomes strongly dependent on nuclear motion which occurs on femtosecond (10−15 s) time scales. Numerical solutions of the time-dependent Schrödinger equation, TDSE, for the one electron \(\mathrm{H}_{2}^{+}\) molecule as compared to the H atom, provide schemes for studying attosecond electron motion in a coherent electron wave packet (CEWP). Ionization of CEWP’s by attosecond laser pulses result in large asymmetries in the ionization yields which follow electron motion and transfer inside CEWP’s. High-order harmonic generation (HHG) is shown to be an even more sensitive tool for monitoring attosecond electron motion using few femtosecond, intense, mid-infrared probe laser pulses. The strong variation of harmonic intensities as function of time delay between the pump pulse (i.e., the pulse which prepared a CEWP) and the probe pulse is interpreted with the help of the Strong Field Approximation (SFA) and the three step recollision model.