Knowledge Bank

Complete Raman and infrared spectral data have been obtained for trans-IHC-CHI and trans-IDC=CDI, including Raman displacements, semiquantitative relative intensities, and quantitative depolarization ratios, as well as infrared wave numbers and relative intensities between 400 to $4000cm-1$. A systematic study of detailed normal coordinate analyses was made for all the eight dihalogenated ethylenes (trans isomers). The most general quadratic potential energy function of the valence force type was used. The results of these calculations indicate that there are systematic variations in the potential energy constants. For example, the carbonhalogen stretching constant $(fy)$ was respectively for the fluorine, chlorine, bromine, and iodine molecules 6.79, 4.21, 3.31, and 2.45 md {\AA}. With the aid of these variations in the potential energy constants, it was possible to calculate the probable values of several unobserved wave numbers. $\mathrm{<mrow\; data-mjx-texclass="ORD">\ast </mrow>}$Present address: University of Illinois at Chicago Circle, Chicago, Illinois, 60680