The first ionization potentials of benzene and benzene-d6 have been precisely determined by the extrapolation of three-photon resonant Rydberg states in the four-photon ionization spectrum of the jet-cooled molecule. The convergence of resolved transitions in two Rydberg series for principal quantum numbers as high as 14 (-h6) and 15 (-d6) establish adiabatic thtesholds of 74573.0 ± 2.0 cm-1, and 74592.5 = ± 1.2 cm-1, respectively. These results are crucial for the understanding of the many excited states of benzene in terms of quantum defect theory. Precise quantum defects have been obtained for several Rydberg series and their variation with principal quantum number is reported. The results strongly suggest that the R‴ series of Wilkinson is derived from aπ(e1g)→ nf±1 Rydberg excitation.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry