Isotope effects in Rb3H(SO4)2 type crystals: Is the proton in the centre of the H bond?

Abstract

Infrared spectra of powdered Rb3H(SO4)2, Rb3D(SO4)2 and isomorphous potassium salts have been recorded between 280 and 20 K in the range 2000–400 cm−1. Only two observations in the infrared spectra that appear to be most relevant to the problem of the large isotope effect are discussed. The first one is the extremely broad OH stretching absorption, which is temperature and mass independent and the other one is the Evans transmission near 940 cm−1 which shows strong temperature dependence. The observed temperature effects are not in agreement with the proposed proton localization at the H-bond centre.