The laser photoelectron spectrum of gas phase p-difluorobenzene

Abstract
Gas phase p-difluorobenzene (PDFB) has been laser ionized from several vibronic levels of its 1B2u first excited electronic state. The vibrational state distribution of the ions generated depends on the vibronic level from which ionization occurs. The fundamental frequencies of five symmetric vibrations; ν2, ν3, ν4, ν5, and ν6, and three asymmetric vibrations; ν8, ν29, and ν30, of the lowest electronic state of PDFB+ have been assigned. Effects due to electronic configuration interaction are observed in the photoelectron spectra. Small peaks are also observed in the spectra which may reflect a change in geometry of the ground state cation.