Gas phase spectra of all-benzenoid polycyclic aromatic hydrocarbons: triphenylene

The jet-cooled laser-induced fluorescence and dispersed fluorescence spectra of the S1(A1')<--S0(A1') transition of triphenylene are reported. The spectra exhibit false origins of e' symmetry which are modeled by performing calculations of Herzberg-Teller coupling using time-dependent density functional theory. It is found that this level of theory reproduces the main features of the observed spectra. The oscillator strength of the strongest band is calculated to be f=7x10(-4). From a combination of theory and the observed upper state lifetime of 41 ns, an estimate of the fluorescence yield is made of PhiF=0.084, in agreement with previous studies in the condensed phase.