The infrared absorption spectra of polycrystalline films of C2H2, C2HD, and C2D2have been examined at 63deg;K in the frequency range between 4500 and 450 cmmdash;1. The spectra of the solid state and the gas phase of the various acetylenes are compared and the appropriate vibrational assignments are made. Several absorptions attributable to combinations of lattice modes and molecular fundamentals were found. The observed multiplet structure of the fundamental vibrations indicates that in the lowhyphen;temperature modification of C2H2and C2D2the molecules are located at sites of C2hsymmetry. Spectra of various solid solutions composed of mixtures of isotopic species were obtained and their significance discussed. The effect of isotopic substitution on the splittings in the ngr;5region led to the conclusion that the dipolemdash;dipole coupling model is sufficient to explain the observed spectra.
展开▼
