Accession Number : AD0679352

Title :   THE INTERSYSTEM CROSSING TO AND THE PHOSPHORESCENCE FROM THE INDIVIDUAL SUBLEVELS OF THE LOWEST TRIPLET STATE IN PYRAZINE AT 1.6K.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY

Personal Author(s) : El-Sayed,M. A.

Report Date : AUG 1968

Pagination or Media Count : 26

Abstract : The observed exponential phosphorescence decay of pyrazine in cyclohexane or benzene matrix at 77K, with lifetime of 18 millisec, is found to change into a complex decay below 10K. At 1.6K, the decay is resolved into three first-order decays of lifetimes 6, 130 and 400 millisec. These lifetimes are sensitive to changes in temperature and magnetic field strength. Two mechanisms are proposed to explain the observed results, but both propose that at 1.6K, the spin-lattice relaxation process between the sublevels of the triplet state is slow compared to the 6-millisec radiative lifetime of the tau y spin sublevel. The recent time-resolved polarization measurements of pyrazine phosphorescence in durene indicate that the second mechanism should be at least partially responsible for the observed results. (Author)

Descriptors :   (*PHOSPHORESCENCE, *AZINES), MOLECULAR ORBITALS, CRYOGENICS, SOLUTIONS(MIXTURES), BENZENE, CYCLOHEXANES, RELAXATION TIME, REACTION KINETICS, ELECTRON TRANSITIONS

Subject Categories : Radiation and Nuclear Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE