FEMTOSECOND SPECTROSCOPY OF THE (2) (1)SIGMA(-MINIMUM STATE OF NA-2 -TIME-DOMAIN AND FREQUENCY SPECTROSCOPY()(U) DOUBLE)

Femtosecond time resolved pump-probe wave packet dynamics in the (2) d ouble minimum state of Na-2 are reported. The experiments were perform ed in a molecular beam with ion Time of Flight (TOF) detection. By Fas t Fourier Transformation (FFT) of the observed time domain data the en ergy spacings of the coherently coupled vibrational levels in the (2) 1 Sigma(u)(+) potential are obtained with an accuracy of 0.02 cm(-1), although an ultrafast laser source with its inherent spectral width wa s used in the experiment. The wavelengths of the pump and probe laser pulses are chosen such that in this two color experiment we can contro l ionisation versus ionisation induced fragmentation. In order to stud y the influence of the potential barrier on a vibrational wave packet motion we performed simulations based on time dependent quantum calcul ations.