ELECTRON KINETIC-ENERGY DISTRIBUTIONS FROM MULTIPHOTON IONIZATION OF NA2 WITH FEMTOSECOND LASER-PULSES

We calculate kinetic energy distribution of electrons which are produced by multiphoton pump-probe ionization spectroscopy of the sodium dimer. The dependence on the delay time between the two femtosecond laser pulses is studied. It is shown that by measurement of the electron spectra at different delay times it is possible to probe selectively the population in different electronic states. The time-resolved electron spectra reflect not only the periodicity of vibrational motion but also the shape of the coherently prepared nuclear wavepackets. The splitting of the packet into two parts which move out of phase gives rise to ''fractional revivals''. This effect can be observed directly in the kinetic energy distribution of the electrons.