Laser flash photolysis of benzene. III. S n←S1 absorption of gaseous benzene

Gaseous benzene was excited by a KrF excimer laser and a transient absorption was observed in the region between 210 and 930 nm. The Sn←S1 absorption spectrum is assigned using time-resolved spectroscopy and the effects of foreign gas. Three peaks have been found and are assigned as follows: 545 nm(1E1u, f∼0.003), 400 nm (1 1E2g, f∼0.02), and 267 nm (2 1E2g, f∼0.08). The observed energies above the ground state are 7.8 eV for the 1 1E2g state and 9.4 eV for the 2 1E2g state. Spectral shapes become sharper and each peak shifts to shorter wavelengths compared with those in cyclohexane solution. The results suggest that the 2 1E2g has a valence character. Other differences between the solution and gas spectra are discussed.