ABSTRACT
Schlotter et al. (1977) reported a cubic intensity dependence of the photoin duced carrier density induced by ruby laser pulses. The results were explained by the photoionization of triplet excitons produced by the fission of two-photonexcited singlet excitons. Since the triplet energy in tetracene is 1.25 eV (Tomkiewicz et al., 1971), the photon energy 1.78 eV, and the band gap 3 eV, the authors argued that triplet exciton photoionization is energetically feasible whereas triplet-triplet ionization is not.
