THE UNIMOLECULAR DECAY OF THE TRIPLET STATE OF ANTHRACENE IN FLUID AND VISCOUS MEDIA: AN EXPERIMENTAL STUDY

Abstract

The rare of decay of the triplet, state of anthracene, dissolved in hexane, tetrahydrofuran and glycerol, has been measured at temperatures ranging from 30 to - $70^\circ C$. In fluid solvents at ordinary temperatures, the decay appears to be chiefly the result of a bi-molecular quenching reaction involving an unknown quencher, present in trace amounts even in highly purified solvents. In addition, there appears to be a unimolecular, temperature-independent decay, corresponding to an intrinsic mean life of about 0.01 sec. In glycerol, the first order rate constant decreases rapidly with decreasing temperature, approaching a limiting half mile of about 0.04 sec. at $-25^\circ C$. For 1, 2, 5, 6 dibenzanthracene, the corresponding half life is 1.3 sec. These limiting values for the mean lives are fairly close to published values obtained for the same compounds in EPA at liquid-nitrogen temperatures.