Multiphoton ionization spectroscopy the neutral S₁←S₀ transition and the ionic state of p-xylene

We present an assigned spectrum of the first electronic transition of p-xylene observed by resonance-enhanced multiphoton ionization in a time-of-flight mass spectrometer. The resulting vibrational populations in the ionic ground state due to different neutral vibronic intermediate S₁ states have been investigated by means of time-of-flight photoelectron spectroscopy. This allows a check of the propensity rules for photoionization of this molecule. The spectrum shows a rich structure and some vibrational frequencies of the ion are determined.