Picosecond pump-probe multiphoton ionization of isolated molecules: IVR and coherence

Picosecond time-resolved multiphoton ionization spectroscopy of isolated trans-stilbene and aniline is reported. Non-exponential decay of trans-stilbene is observed and evidence for vibrational energy redistribution is presented. The rate of IVR is found to be about 0.5 × 10^(12) s^(−1) at 296 K. The excess energy dependence of the isomerization rate is determined for total vibrational energy of 2000–4500 cm^(−1). Comparison with calculated thermally averaged rates and beam data is made