Observation and assignment of the hydrogen bond exchange disrotatory in-plane bending vibration v5 in (HF) 2

Abstract

We report far-infrared spectra between 100 and 300 cm −1 for (HF) 2 under equilibrium conditions in hydrogen fluoride vapour (243 K, 1.2–1.7 kPa). The spectra were obtained by high-resolution interferometric Fourier transform techniques (resolution 0.007 to 0.012 cm −1 fwhm unapodised) using a new 2.6 m high transmission light pipe cell and a 10 m long path cell. The K = 3, A + sublevel of the large-amplitude disrotatory in-plane bending fundamental v 5 of (HF) 2 is assigned at 393.550 cm −1 by analysis of the perpendicular K = 3 ← 2 subband near 275.4 cm −1 and the parallel K = 3 ← 3 subband near 157.1 cm −1. The results are compared with recent theoretical predictions.