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The Structure of Pb+ Laser Centres in KMgF3 from Optically Detected Electron Spin Resonance and Electron Nuclear Double Resonance

Laser action of X-rayed lead doped KMgF3 crystals from an unknown defect was recently reported by Horsch and Paus.1 By applying optical detection of ESR and ENDOR, the structure of two very similar laser active Pb centres could be determined from the selectively measured hyperfine and superhyperfine interactions. They consist of a Pb+ substituting for a K+ next to an F− vacancy along with a next nearest K+ vacancy for charge compensation in two different positions (Pb+(1) centres). The absorption band for the excitation of the laser emission at 1.4eV could be identified from the optical excitation spectra and from a special magneto-optical ESR technique. The structural properties, as well as the explanation of their laser properties within a crystal field model, are analogous to those of Tl0(1) centres in alkali halides and Pb+(1) centres in alkaline earth fluorides. A Pb++ perturbed FA centre was also observed.