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 approxi mative Gaussian wave packet (GWP)-method applied to the coherent excit ation of molecules to numerically exact solutions of the lime-dependen t Schrodinger equation. The results imply that the short-time vibratio nal dynamics of molecules upon femtosecond excitation can be described accurately within the GWP-method. This especially holds for the calcu lation of femtosecond pump/probe signals, which are much less sensitiv e to the errors of the method than the wave function is. (C) 1998 Amer ican Institute of Physics. [S0021-9606(98)01021-6].