ON THE LOW-LYING RYDBERG STATES OF AZABENZENES

Mass resolved excitation spectra of supersonic expansion cooled mono- and diazabenzenes are reported for the low lying Rydberg states. Transitions are located for pyridine, pyrazine, and pyridazine, but not pyrimidine. The Rydberg state lifetimes of these molecules are estimated, based on a Lorentzian line shape analysis, to be ca. 500 fs. Ab initio calculations for pyrazine at the complete active space self-consistent-field (CASSCF) and CASSCF many-body second-order perturbation theory (CASSCF/MBPT2) levels show that extensive configuration interaction and dynamic electron correlation are necessary to account for the excited states of these systems. (C) 1995 American Institute of Physics.