Theoretical calculations on the three-photon absorption spectrum of benzene

The three-photon absorption spectrum of benzene is discussed by means of molecular orbital calculations of allowed and vibronic three-photon intensities to S1 and S2. The coupling mechanisms responsible for vibronic absorption to these states are described and it is found that vibronic pathways peculiar of the three-photon process may occur. Allowed intensities to S1, S2 and S3 are in agreement with qualitative expectations from the alternant hydrocarbon theory. On the whole, the S0-->S1 three-photon calculations provide a good basis to discuss available experimental data.