Photoemission from Single Crystal of Pyrene and Nitropyrenes.
Abstract
Photoemission studies were carried out on single crystals of pyrene, and on 1 and 2-nitropyrene. Use was made of double quantum external photoelectric effect (DQEPE) in which a low energy metastable state of the crystal is ionized by combining with another low energy state. By measuring the maximum kinetic energy of the emitted electrons and the light intensity dependence of the yield, it is possible to deduce the energies of the metastable states and even their dynamical properties, in the case of excitons. In the case of pyrene, evidence was obtained for a mobile relaxed excimer state at 2.8ev, a mobile excited excimer state at 3.1ev,and excited monomer state at 3.3ev. The photoemission threshold energies of 1-nitropyrene and 2-nitropyrene were found to be 5.6 +/- 0.1ev and 5.8 +/- 0.05ev, respectively. The band gaps of 1 and 2-nitropyrene are estimated to be 3.4ev and 3.7ev respectively. Preliminary evidence was obtained for a DQEPE in 2-nitropyrene involving a free electron and a triplet exciton at 2.2ev.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1990
- Bibcode:
- 1990PhDT.......262S
- Keywords:
-
- Chemistry: Physical; Physics: Optics; Physics: Condensed Matter