Infrared Absorption of OH⁻ in NaCl Crystal

Abstract

Temperature dependence of the infrared absoption spectrum of the OH⁻ molecular ion in NaCl crystal has been observed at a temperature range from 1.45 to 4.2 K. Two intense absorption peaks at 3651.2 and 3655.2 cm⁻¹ are analyzed to be due to the stretching vibrational level combined with the low-lying levels of the translational motion of the center of mass of the OH⁻ molecular ion between the [100] off-center sites. The validity of the values of the parameters of the translational motion has been verified which were recently determined by the millimeter wave spectroscopic experiment (preceding paper). A side band in the infrared absorption spectrum which grows at 3653.2 cm⁻¹ quadratically with the OH⁻ concentration is identified as a dimer band of the OH⁻ molecular ions.