Anharmonische Konstanten von SiHCl_3 und CHCl_3

摘要

Most of the anharmonic constants of trichlorosilane and -methane have been determined, with special emphasis to the values of x_(1i), i = 1 to 6. In both molecules, there is a strong Fermi resonance between hydrogen stretch and bend vibrations and Coriolis interaction between v_2 and v_5. Some irregularities in the hot band structures point to an interaction of v_1 with v_2 + 2 v_4 and other higher order interactions. In SiHCl_3, x_(13) and x_(16) are near 0, in agreement with a rule that nondiagonal anharmonicities between high- and low-frequency vibrations tend to be small. In CHCl_3, the corresponding values are larger, though still small. We discuss a possible correlation of such values with the frequency change of one of the vibrations, if the bond corresponding to the other one is dissociated. Ni(CO)_4 is quoted as a further example. The data set could help in calculations of vibrational relaxation rates.