FEMTOSECOND TIME-RESOLVED 2-PHOTON IONIZATION SPECTROSCOPY OF K-2

We investigated the coherent motion of vibrational wave packets in the \B> (1) Pi(u) state of the potassium dimer applying two color pump/pr obe spectroscopy with a sub 100 fs time resolution. Special interest w as paid to the ionization probe step which was analyzed carefully by v arying the probe energy over a wide range. Time-dependent quantum calc ulations explain the experimental outcomes by introducing a nonconstan t transition dipole moment between the \B> and the ionic state \X+> an d by taking into account the excitation of long lived autoionizing Ryd berg states. (C) 1997 American Institute of Physics. [S0021-9606(97)02 647-0].