Quantum Mechanical Calculations of the U-Center force Constants

Abstract

It is now well known that a hydride ion can replace a halide ion in alkali-halide crystals. The resulting defect, the U center, gives rise to absorption lines or bands in both the ultraviolet and infrared regions of the spectrum. Absorption in the former region is associated with electronic transitions between localized levels, while that in the latter region is associated with a localized vibrational mode whose frequency lies well above those of the transverse optical branch. Properties associated with electronic transitions have already been extensively investigated,(1) whereas the vibrational properties associated with the local mode have only recently received much attention.(2)