Jan HRUSAK (J. Heyrovsky Inst. Phys. Chem. and IMS), Detlef SCHRODER (Tech. Univ. Berlin) and Suehiro IWATA
[J. Chem. Phys. 106, 7541 (1997)]
The ionization of the phenyl radical C6H5· (2A1) is examined by high level theoretical means. On the basis of a comparison of MCSCF, B3LYP, and CCSD(T) results, the ground state of the phenyl cation is definitely identified as C6H5+ (1A1) with a conservative estimate of 8.1 ± 0.1 eV for the associated adiabatic ionization energy for the transition C6H5· (2A1) -> C6H5+ (1A1). The lowest lying triplet state C6H5+ (3B1) is ca. 0.8 eV higher in energy, but yet the theoretical results suggest that formation of triplet cation is favored in photoionization experiments because the Franck-Condon factors are much favorable for the transition C6H5· (2A1) -> C6H5+ (3B1) as compared to generation of the singlet ground state C6H5+ (1A1). These features are revealed in the calculated photoionization spectra of [D0]- and [D5]-phenyl radical to yield either singlet or triplet cations.