Rydberg states (n = 4–29) of azabicyclo [2.2.2] octane as studied by two-color fluorescence DIP and multiphoton ionization spectroscopies

Two-color fluorescence dip and multiphoton ionization (MPI) spectra have been observed for azabicyclo 2.2.2] octane in a supersonic jet. The spectra showed well-resolved structures consisting of five Rydberg series of n = 4–29. The five Rydberg series were assigned to s, p_z, p_xy, and two d orbitals. From the spectra obtained after exciting the molecule to various vibronic levels in the S₁ (3s) state, the Δν = 0 selection rule was obtained for the Rydberg-Rydberg transition. The same selection rule was found to be preserved also for the transition from the S₁ state to the ion. It was shown that the autoionization of the high Rydberg states to the ion is governed by Δν=?1. The existence of a very fast non-radiative channel was found for the Rydberg state from the ω₂ power dependence on the two-color MPI spectra.