Femtosecond time-resolved four-wave mixing (FWM) spectroscopy is perfo
rmed using degenerate laser frequencies in order to investigate molecu
lar dynamics in iodine molecules in the gas phase. It is demonstrated
that by varying the timing as well as the wavenumber position for the
signal detection different dynamics can be accessed. This is due to a
selection of contributions (e.g. described by Feynman diagrams) to the
nonlinear polarization of the process. The wave packet dynamics of th
e electronic excited B as well as the X ground state of iodine can be
monitored by degenerate FWM, coherent anti-Stokes Raman scattering or
coherent Stokes Raman scattering (CSRS) processes all included in the
same experiment. (C) 1997 Elsevier Science B.V.