Vibrational levels of p-xylene cation determined by mass-analyzed threshold ionization spectroscopy

Mass-analyzed threshold ionization (MATI) spectroscopy and two-color resonant two-photon ionization method were used for the determination of the vibrational levels of the p-xylene cation. The MATI spectrum was recorded via the 00 vibrationless level of the S1 state of p-xylene. The spectrum shows a rich structure and some vibrational frequencies of the cation are determined. The experimental findings are well supported by ab initio calculation.