PROTON TUNNELLING IN CHROMOUS ACID

Abstract

The infrared absorption spectra of CrOOH and CrOOD are analysed using a model potential consisting of two back-to-back Morse functions. The v s(OH) band of CrOOH at 1950 cm-1 is assigned as a |1> → |2> transition and the 226 cm-1 band in the far infrared as a |0> → |1> tunnelling mode. The v s(OD) doublet of CrOOD, with peaks at 1923 cm-1 and 1613 cm-1, arises from |0> → |3> and |1> → |2> transitions, as suggested originally by Snyder and Ibers. Approximate v s(OH) and v s(OD) band shapes are calculated. The lack of temperature dependence of the 1650 cm-1 v s(OH) band of CrOOH suggests that a ferrodistortive phase transition occurs slightly below room temperature.