Molecular femtosecond excitation described within the Gaussian wave packet approximation

We consider the ultrashort pulse excitation of molecules within bound electronic states. Using ultraviolet (UV) electronic and intense pulse infrared (IR)-excitation as numerical examples we compare the approximative Gaussian wave packet (GWP)-method applied to the coherent excitation of molecules to numerically exact solutions of the lime-dependent Schrodinger equation. The results imply that the short-time vibrational dynamics of molecules upon femtosecond excitation can be described accurately within the GWP-method. This especially holds for the calculation of femtosecond pump/probe signals, which are much less sensitive to the errors of the method than the wave function is. (C) 1998 American Institute of Physics. [S0021-9606(98)01021-6].