Experimental evidence for the influence of excition interactions on the temporal decay of crytalline tetracene flourescence

Crytalline tetracene fluorescence was excited at room temperature by high intensity picosecond pulses at 531.5 nm (ca. 10¹⁵ photons cm^?2 per pulse). The analysis of the decay curves during the first 1.5 ns at high excitations, shows a decay faster than the singlet lifetime measured at low intensity, due to singlet quenching by S–S and S–T interactions, and the appearance of a slow decay due to singlets generated by T–T interactions. Numerical fitting is obtained with rate constants γ_SS and γ_SS equal to 5 × 10 ^?9 cm³ s^?1 within a factor of approximately two.