Cross Relaxation between the Spin Levels of Phosphorescent 1,2,4,5-Tetrachlorobenzene and Photochemical Products of the Durene Host.
Abstract
At certain magnetic fields, intensity changes have been observed in the phosphorescence of 1,2,4,5-tetrachlorobenzene (TCB) doped in a single crystal of durene cooled to 1.6 K. These changes are found to result from cross relaxation (CR) processes between the spin levels of the lowest triplet state of TCB and the spin levels of a photochemically produced spin system. Experiments show that the presence of duraldehyde within the host crystal of durene is important for the production of the observed photoproducts. Following the application of a magnetic field of the proper magnitude and direction to induce CR, the phosphorescence intensity of TCB displays an observable time behavior. There is a sharp rise in phosphorescence intensity, followed by a fast decrease and finally a slow exponential decay to a new steady state, which is higher in intensity than that observed in the absence of CR. Rate equations describing the time behavior of the populations of the various spin levels are derived and solved numerically. From the calculated triplet state populations as a function of time, it is possible to calculate the time behavior of the phosphorescence intensity. Results of experiments and calculations suggest that the photoproduct responsible for the CR is doublet spin system with a spin lattice relaxation time of approximately 18 seconds at 1.6K. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1977
- Accession Number
- ADA041008
Entities
People
- Mostafa El-Sayed
- William M. Pitts
Organizations
- University of California, Los Angeles