Compensation of Trivalent Europium and Ytterbium Ions in Calcium Fluoride by Interstitial Hydride Ions

Abstract

Hydrogen has been diffused into calcium fluoride crystals doped with Eu, Yb and other Rare Earths. The local mode absorption from H-ions has been measured before and after X-or y-irradiations and a detailed study has been made of the new electronic transitions of Yb3+ ions near 1 pm which appear after the irradiation. It is concluded that for Eu and Yb dopings, RE3+-H-(i) pairs are produced which are thermally unstable. In CaF,:Yb crystals, a second centre involving two hydride ions has also been identified.On a fait diffuser de l'hydroghne dans un cristal de fluorure de calcium dope avec Eu, Yb, et les autres terres rares. On a mesurB l'absorption provenant des modes locaux des ions H-, avant et aprhs irradiation par des rayons X et y, et on a BtudiB en detail, les nouvelle transitions Blectroniques des ions Yb3+ au voisinnage de 1 pm, qui apparaissent aprhs irradation. Pour les cristaux dopes avec Eu et Yb, on peut conclure qu'il y a production de paires T.R.3+-H-(i) thermiquement instables. Dans les cristaux dopes avec Yb on a pu identifier aussi un second centre faisant intervenir deux ions hydrures.

Spectroscopy of Ionic Crystals: The Hydrogenated Calcium Fluoride System

“…Chambers and Newman (1969) correctly surmised that the four lines are two pairs: one associated with the ground state of the erbium ion and the other with a low-lying crystal field level of erbium. Edgar et al (1979) determined from optical studies that this low-lying level was 4·5 cm -1 above the ground level for the hydrogenic site, 2·7 cm-1 for the deuterium site and 2·2 cm-1 for the tritium site, and hence is appreciably populated down to 4 K. In the absence of any electron-phonon interaction effects there would be two coincident pairs of lines in the local mode spectrum, but the different electron-phonon interaction shifts for the two crystal field levels result in non-coincidence and four distinct lines in the spectrum.…”