FORMATION OF TRIPLET STATE OF NAPHTHALENE IN PULSE RADIOLYSIS OF GASEOUS MIXTURES OF BENZENE AND NAPHTHALENE

A significant yield of the lowest triplet state of naphthalene is observed when 1.9 atm benzene containing small amounts of naphthalene is pulse irradiated in the gas phase at 120°C. The yield is independent of naphthalene concentration from 0.3 mole % to at least 3 mole %. Electron scavengers (SF 6 and CCl4) decrease the yield by 70%, as does a positive-ion scavenger, triethylamine. This 70% is thought to originate by neutralization of C10H3+ by C 10H3-. The other 30% of the triplet yield is thought to originate from benzene (3B1u) formed directly by the irradiation of the benzene vapor. Naphthalene was found to be 34±4, 38±4, and 18±2 times more efficient in accepting energy from the benzene triplet than transbutene-2, cyclohexene, and nitromethane, respectively. Similar results were obtained using 1.3 atm argon as the main gas, with about 3 mole % benzene and about 3×10-3 mole % naphthalene present at 25°C. In this case, the naphthalene triplet was formed after the pulse, and kinetic analyses of the curves as a function of naphthalene concentration allowed an evaluation of the benzene ( 3B1u) decay constant of 1.3×105 sec -1 at 18 torr benzene (which decreases with increasing benzene pressure) and of the rate constant for energy transfer from benzene ( 3B1u) to naphthalene of (3.0±0.5) ×10 11 liter mole-1-sec1. Naphthalene was found to be 20±3 times more efficient than trans-butene-2 in accepting energy from triplet benzene. Copyright 1969 by the American Institute of Physics."