Electron Spin Resonance of theZ1Band in KCl with SrCl2

Abstract

The electron spin resonance (ESR) associated with the ${Z}_{1}$ optical absorption in KCl: Sr has been observed in association with the $F$-center ESR. By an extrapolation procedure, it is found that the ${Z}_{1}$ ESR is characterized by a $g$ value of 1.9952\ifmmode\pm\else\textpm\fi{}0.0005 and a derivative peak-to-peak width of 63\ifmmode\pm\else\textpm\fi{}1 Oe. A Gaussian shape for the ${Z}_{1}$ ESR is strongly inferred. Preliminary results obtained with $F$ and ${Z}_{2}$ centers present indicate that the ${Z}_{2}$ ESR has a slightly larger $g$ value and a somewhat greater width than the ${Z}_{1}$ ESR. Optical absorption parameters of $h{\ensuremath{\nu}}_{max}=2.068\ifmmode\pm\else\textpm\fi{}0.005$ eV (599 m\ensuremath{\mu}) and $W=0.290\ifmmode\pm\else\textpm\fi{}0.005$ eV are found for the ${Z}_{1}$ band at liquid nitrogen temperature.The ESR results are compared to earlier measurements by Kawamura and Ishiwatari. An attempt is made to interpret the results by comparing Seitz's model of the ${Z}_{1}$ center to the $F$ center. There are tentative indications that Seitz's model may be appropriate, but the calculations are not yet sufficiently refined to establish the model with any degree of certainty. An estimate is made of the rather large hyperfine interaction to be expected for ${Z}_{1}$ centers containing ${\mathrm{Sr}}^{87}$ nuclei.