Dirk Schoemaker

Pb++ as a hole trap in KCl: ESR and optical absorption of Pb+++

Abstract It is shown that the Pb++ ion in KCl can stabilize the hole from a mobile Cl-2 center and form Pb+++(2S 1 2 ). The ESR spectrum of Pb+++ is characterized by g = 2.034 ± 0.001 and A (207 Pb = 33.0 ± 0.1 GHz, and the optical absorption bands are situated at 465 nm, 303 nm, and 216 nm.

Librational motion of the H /sub lambda/(Li/sup +/) center in KCl

It is shown from the analysis of some subtle features of the ESR spectra that the Cl/sub 2//sup -/ axis of the H/sub A/(Li/sup +/) center in the KCl:Li/sup +/, which makes a 26/sup 0/ angle with a (100) direction, does not lie exactly in a (110) plane at 4.2/sup 0/K, but lies outside it by about 1.5/sup 0/. Such a geometry implies the existence of a librational motion over a 3/sup 0/ angle. The behavior of the ESR lines both as a function of temperature and under (110) uniaxial stress indicates that such a motion exists, and that it is very likely a tunneling motion at 4.2/sup 0/K with a rate of about 1 x 10/sup 7/ Hz. (auth)