Femtosecond spectroscopy of heterogeneous electron transfer: Extraction of excited-state population dynamics from pump-probe signals

Numerical calculations of pump-probe signals corresponding to excited-state absorption of the molecular state are presented. The molecular excited-state decays due to ultrafast electron injection into a continuum of electronic states (semiconductor levels) and the model calculations take into account the consequent molecular reorganization. A time-dependent Schrödinger wave equation approach is utilized to model the pump-probe dynamics. The continuum of semiconductor states, namely, its conduction-band levels, is described by an expansion in terms of orthogonal polynomials. It is shown that excited-state dynamics, including information on the modulation of population transfer due to vibrational coherences, can be unambiguously deduced from the pump-probe signals.