| Interesting rovibrational characteristics of two D 3h oblate symmetric top molecules were studied. Hamiltonian models for the fine rovibrational level structure of [1.1.1]propellane (propellane) were obtained for many low-lying modes. Ground state parameters (GSP) that are not exclusively K2n dependent were obtained. Initially, the GSP were used in conjunction with density functional (DFT) values of the exclusively K2n dependent parameters C0, and De. Coriolis h1,1 (DeltaK = +/- 1, Delta l = +/- 1) interactive fundamentals nu15 and nu 12 were analyzed; complementary use of transition energies and line intensities allowed an experimental value of the Coriolis parameter to be assessed. In another phase of the project, a global fit of the nu10 , nu11, and nu14 fundamental bands and the nu 11-nu18 and nu10-nu18 bands was performed. The h1,1 interaction between the close proximity rovibrational states of nu11 and nu14 results in energy shifts and large distortions of line intensities in the nu 11 band, and these characteristics were reproduced. Splitting of the otherwise degenerate A1 and A 2 states that are the highest in frequency for a given J manifold was observed for the h1,1 coupled nu 11 /nu14 triad composed of the |k| = 3 levels of nu14, the kl = + 4 levels of nu11, and kl = -2 levels of nu 11. Significant splitting of the kl = -2 levels in combination with h1,1 are important in the noted lifting of degeneracies. Another interaction, this one between nu14 and what is presumably the IR inactive nu16/nu 3 singly excited dyad, results in a significant bifurcation of the K levels of nu14 for a given observable J manifold. Another interaction, h5,-1, between nu 14 and nu11, made it possible to find C 0 and DK0, parameters not available from analysis of transitions from the ground vibrational state to singly excited fundamentals in the absence of higher order interactions. In studies of another D3h oblate top, BF3, effects of anharmonic interactions on the band origin of the symmetric stretching mode were examined using coherent anti-Stokes Raman spectra of 10BF 3 and 11BF3. Upon isotopic substitution, the magnitude and direction of the anharmonic shifts of each fundamental were observed to be consistent with DFT results. |
