In this contribution the measurements of a single shot femtosecond laser pump-probe technique on substituted benzalacetones are reported. The technique is based on counter propagating femtosecond laser pulses in a supersonic beam of low density of sample molecules and simultaneous probe detection by ion or fragment ion formation through a reflectron time-of-flight
mass spectrometer. The application of this technique to medium sized organic molecules reveals some insight into the electron transfer process during ionization through a
multi photon absorption procedure.