Luminescence of F Centers in Alkali Halides under Hydrostatic Pressure

Thumbnail Image
Brothers, A. D.
Lynch, David
Major Professor
Committee Member
Journal Title
Journal ISSN
Volume Title
Research Projects
Organizational Units
Organizational Unit
Journal Issue
Is Version Of
Physics and Astronomy

F-center luminescence spectra have been measured at 78°K in NaCl, KCl, KBr, KI, RbCl, and CsBr under hydrostatic pressure to 3.5 kbar. From a comparison between the shift of the emission peak with pressure and the shift with temperature, it is concluded that most of the latter arises from the electron-lattice interaction and not from thermal expansion. This is the opposite of the conclusion for F-center absorption, for which thermal expansion dominates the temperature coefficient of the peak energy. The halfwidth of the function W(E), the probability per unit time of emitting a photon with energy between E and E+dE, does not vary with pressure in NaCl, KCl, and RbCl, but the half-width of the "shape function," E−3W(E), changes with pressure. This is interpreted as meaning that for F-center emission, it is more suitable to make the Condon approximation on the momentum operator than on the position operator. Lifetime measurements in KCl under pressure at 15 and 78°K give the pressure derivative of the thermal ionozation energy of the relaxed excited state of the F center in KCl, + 19×10−6 eV bar−1. The pressure coefficients of a few K- and L-band peaks have been determined. These provide additional evidence that the final states in the L-band transitions are not similar to those for F- and K-band transitions. The K band in RbCl changes shape with pressure. The FA-band splitting has been found to increase with pressure in KCl:Na. The F-center emission in KBr under pressure has been found to have two components, and the excitation spectrum has two peaks, the F band and a peak very close to the K′band previously found in absorption at much higher pressures. Emission data at 12°K on diverse samples of additively colored KBr strongly suggest that there are two components to the normal F-center luminescence in KBr with no applied pressure.


This article is from Physical Review 164 (1967): 1124, doi:10.1103/PhysRev.164.1124. Posted with permission.

Sun Jan 01 00:00:00 UTC 1967