EPR Optical Detection of F Centre Pairs in Alkali Halides I. Pumping Cycle Kinetics and Characteristics of the Resonances

✍ Scribed by Y. Ruedin; P.-A. Schnegg; C. Jaccard; M. A. Aegerter

• Publisher: John Wiley and Sons
• Year: 1972
• Tongue: English
• Weight: 695 KB
• Volume: 54
• Category: Article
• ISSN: 0370-1972
• DOI: 10.1002/pssb.2220540220

✦ Synopsis

Abstract

The electron paramagnetic resonance of F centres in the ground and excited states has been optically detected in the following alkali halide crystals: NaCl, KF, KCl, KBr, KI, RbBr, and RbI. A decrease of the radiative quantum efficiency of the F centre luminescence is observed when microwave transitions are induced between the spin levels. The mechanism responsible for this effect is an electronic tunnelling through the crystal field potential; the electron in the relaxed excited state of an F centre (F̃*) is transfered non radiatively to another nearby F centre in its ground state (F~0~), and leads to the momentary formation of an α and an F′ centre. Such a process is a function of the total spin of the F̃*‐F~0~ pair. The role played by the paired centres is confirmed by measurements at different F centre concentration. Moreover at high optical excitation pumping rate the population of the intermediate complexes (F′‐α) is large enough to allow an estimation of the rate of the reverse process F′ + α → F~0~ + F~0~.