Mass-analyzed threshold ionization spectroscopy of 1-bromopropane through dissociative intermediate states

One-color two-photon ionization of 1-bromopropane, resulting in the 1-C3H7Br+ ions in the X ˜ 1 2 E 1 / 2 and X ˜ 2 2 E 1 / 2 electronic states, is investigated using mass-analyzed threshold ionization (MATI) spectroscopy. The adiabatic ionization energies of two spin states are found to be 82 257 ± 5 and 84 823 ± 5 cm−1, respectively. The two-photon MATI spectrum exhibits an extensive vibrational structure. The active modes, including the C–Br stretching, the CH2–Br wagging, the CH2 and the CH3 rocking modes, are observed and reliable values for these vibrational frequencies are obtained. We have also performed ab initio and density functional calculations, which provide interpretation for our experimental finding.