Infrared and Raman polarized spectra of ammonium hydrogen bis(trichloroacetate) single crystal

Abstract

The polarized infrared and Raman spectra of ammonium hydrogen bis(trichloroacetate) single crystal have been investigated in the 4000–350 cm−1 and 4000–10 cm−1 range, respectively. The infrared spectra have been measured at room and low temperatures. An assignment of the bands in terms of approximate type of motion is given. The asymmetric stretching vibration, vaOHO, of the strong hydrogen bond gives rise to a very broad infrared absorption, with a maximum around 800 ± 50 cm−1, which is polarized strictly along a tetragonal Z(c) direction of this crystal. For this vibration a correlation field (Davydov or factor group) splitting is not observed. The out-of-plane deformation vibration, γOHO, obeys selection rules for the C2 site symmetry group. This result and also an interpretation of the vC=O vibration strongly suggest that a potential energy function of the strong hydrogen bond has a single symmetric minimum.