Vacuum ultraviolet laser pulsed field ionization photoelectron study of cis-2-butene

The vacuum ultraviolet pulsed field ionization photoelectron spectra of supersonically cooled cis-2-butene was measured. The apparatus consists of vacuum ultraviolet laser system, a pulsed molecular beam source, a pulsed field ionization-photoelectron (PFI-PE) detector, and a time-of-flight mass spectrometer. The timing sequence for opening of the pulsed valve, firing of the lasers, and applying the PFI field is controlled by two digital delay units. Using the ab initio vibrational frequency calculations the vibrational bands observed for cis-2-butene cation were assigned in their ground state.