Simultaneous rovibrational analysis of the nu(2), nu(3), nu(5), and nu(6) bands of (H3CF)-C-12

A total of 4892 transition wavenumbers of the v(2), v(3), v(5), and v(6) fu ndamental bands of (H3CF)-C-12 and 1469 frequencies of the rotational trans itions in the v(2) = 1, v(3) = 1, v(5) = 1, and v(6) = 1 vibrational states have been fitted simultaneously by taking explicitly into account various Coriolis interactions, l-type interactions, and at-resonance terms between and within the vibrational states. The standard deviation of the fit using 71 parameters was 8.10 x 10(-5) cm(-1) for the infrared data and 0.198 MHz for the rotational data. This study clearly shows that in order to obtain a really quantitative fit of the highly precise data of vibration-rotational and rotational spectroscopy, it is necessary to fit all the data simultane ously using a variational approach. The deperturbed values of the upper sta te rotational constants differ significantly from those obtained previously in fitting the v(3) and v(6) bands as isolated bands and the v(2)/v(5) ban ds by a variational approach. This is important for the precise determinati on of the equilibrium structure of methyl fluoride (J. Demaison, J. Breidun g, W. Thiel, and D. Papousek, Struct. Chem., in press). Besides this, the r esults can be used in further studies of the reduced Hamiltonians for more complicated systems of interacting vibrational levels, (C) 1999 Academic Pr ess.