VIBRATION SPECTRA OF $ClF_{3}$ AND $BrF_{3}$

Abstract

The interhalogens, $ClF_{3}$ and $BrF_{3}$, were originally assigned a pyramidal structure of symmetry $C_{3{v}}$ on the basis of electron diffraction studies. Early vibrational spectra were also interpreted in terms of this model. More recently, however, investigation of $ClF_{3}$ by x-ray diffraction and microwave spectroscopy, indicates that this molecule is plane and of symmetry $C_{2{v}}$; the angles being nearly right angles. We have studied the infrared spectrum of $ClF_{3}$ vapor from 3 to 38$\mu$ and its Raman spectrum. These data provide a strong confirmation for the plane structure. The fundamental frequencies obtained in the present work, together with the moments of inertia from the microwave results lead to a calculated entropy in good agreement with that obtained from thermal measurements. The spectral data obtained for $BrF_{3}$ are less complete but the similarity of its infrared spectrum to that of $ClF_{3}$ suggests that it also has the plane $C_{2{v}}$ structure.