VIBRATION-ROTATION BANDS OF SOME SMALL MOLECULES UNDER HIGH RESOLUTION

Abstract

A survey will be made of measurements carried out during the past few years at Oxford on some vibration-rotation bands of a number of simple diatomic and polyatomic molecules, using high resolving power. A grating spectrometer has been used mainly in the region 2-6 $\mu$ with photoconductive cells as detectors. At 5$\mu$ it is possible to resolve sharp lines about $0.1 cm^{-1}$ apart. Various rotational and vibrational constants have been derived, such as the rotational constants $B_{i}$, $B_{e}$, the centrifugal stretching constants $D_{J}$, $D_{JK}$, the $\ell$-doubling factors q and Coriolis factors $\zeta_{i}$. The bond lengths of some carbon-carbon linkages have been determined, and the effects of Fermi resonance have been examined. The molecules which have been studied include hydrogen and deuterium halides, acetylene and deuteroacetylenes, hydrogen cyanide and deuterium cyanide, methyl acetylene and its deutero derivatives, cyanogen diacetylene, allene and allene-$d_{4}$, deuteromethanes, dimethyl acetylene, methyl halides, diazomethane and keten. The results derived from this work have been correlated with other infra-red and Raman measurements.