MATI and PIRI studies of the X̃ and à state of trans-1,3-butadiene cation

The VUV-MATI spectrum of trans-1,3-butadiene (BD) has been recorded and analyzed. The lowest ionization potential is 73.143 cm−1. The assigned vibrational bands agree well with previous measurements, and three new bands are assigned. Fragment PIRI experiments were carried out on the Ã(2Au)←X̃(2Bg) transition in BD+, and the optical spectrum was analyzed. Information regarding the fragmentation mechanisms that characterize the observed optical spectrum is presented. At low PIRI-photon energies, the fragmentation process is a one photon process yielding primarily C3H3+. As the PIRI photon energy increases, more and more C2H4+ is produced, indicating that the two-photon process producing this fragment involves the D̃ state.