FORMATION OF PROTONATED AMMONIA CLUSTERS PROBED BY A FEMTOSECOND LASER

Femtosecond pump-probe techniques combined with a reflectron time-of-flight mass spectrometer are employed to investigate the formation mechanisms of protonated ammonia clusters. Pump pulses are employed to excite the ammonia clusters to electronically excited states corresponding to selected A or C' states, while probe pulses with variable delay times are used to ionize the clusters. The results reveal that both the absorption-ionization-dissociation and absorption-dissociation-ionization mechanisms occur in the A state, while the absorption-ionization-dissociation mechanism is the sole one operative in the C' state.