Abstract
The O—H stretching band and its immediate sidebands have been studied for O impurities in NaCl, KCl, RbCl, KBr, KI, and NaBr from 1.4 to 300°K. Sideband splittings range from 12 in NaCl:O to 37 in KBr:O, and correlate with dips in the low-temperature thermal conductivity and with far-infrared absorption bands. Preliminary results on the electric-field-induced dichroism in KCl:O and RbCl:O give a dipole transition moment perpendicular to the O—H axis for the main sideband. There is evidence that several sidebands in NaCl:O are themselves combination bands with one or more 2-3- tunneling levels. The first overtone yields values of and for O in KBr. These values explain very well the O/O isotope shift of the main stretching band in KBr and KCl. The main-band oscillator strengths are small, on the order of 5× for most crystals, but this value is consistent with a theoretical calculation of the dipole moment by Cade. The main bands broaden rapidly with increasing temperature, possibly indicating a prominent lifetime-limiting role played by the sideband levels. The sideband levels themselves are tentatively suggested to be due to a center-of-mass resonance in KBr:O and to a librational resonance or fast tunneling level in KCl:O.
- Received 31 July 1968
DOI:https://doi.org/10.1103/PhysRev.177.1274
©1969 American Physical Society