Heterogeneous perturbations in the Doppler-free S1 ← S0 two-photon spectrum of benzene: Evidence for intrastate coupling

Rotational perturbations are identified in Doppler-free two-photon
spectra of the 1410 and 1410110 vibronic bands in C6H6. Evidence is
found that Coriolis coupling between some of the rotational levels
of two distinct vibrational states within S1 is the mechanism
responsible. This coupling mechanism is thought to be responsible
for irreversible intramolecular relaxation at higher excess
energies and higher vibrational state densities.