The electronic spectra of phenyl radicals

Abstract

An electronic absorption spectrum, attributed to phenyl, has been observed in the visible region with origin at 18 908 cm^-1 after flash photolysis of benzene and halogenobenzenes. Similar spectra of fluoro, chloro and bromo phenyl are observed after flash photolysis of disubstituted benzenes. The vibrational structure of the phenyl spectrum has been analysed in terms of two fundamental frequencies at 571 and 896 cm^-1 which correspond to the e_2g and a_1g frequencies of the B_2u state of benzene. The ground state of phenyl has a π⁶n electronic configuration and the observed transition is interpreted as ²A₁ → ²B₁ resulting from a π → n excitation.