The direct l-type resonance spectrum of CF3CCH in the vibrational state v10Z3: Extension of the theory of reduction to H6n terms

The direct l-type resonance spectrum of CF3CCH has been measured in the v10Z3 vibrational state by means of waveguide microwave Fourier transform spectroscopy in the range 8–26 GHz. Three types of direct l-type resonance transitions induced by the (DkZDlZG2) interaction could be observed: 140 transitions following the DJZ0, DkZDlZG2, DjljZ0, selection rule covering values of JZ17–61 and GZjkKlj from 1 to 7, 94 transitions following the DJZ0, DkZDlZG2, DjljZG2, selection rule covering values of JZ26–57 and G from 15 to 24, 90 transitions following the DJZ0, DkZDlZG4 selection rule covering values of JZ34–80 and G from 3 to 12 and 13 transitions following the DJZ0, DkZDlZG6, kZH1, lZH15kZG5, lZG3 selection rule for JZ71-83. 14 A1–A2 splitting transitions with klZC1 were measured from JZ33 to 49. Strong perturbations due to D(kKl)ZG3 interactions made possible the observation of perturbation-allowed transitions with selection rule kZG4, lZG35kZG3, lZH1. Furthermore, the rotational transitions JZ2–1, 3–2 and 4–3 have been measured. To make use of the multiple fitting concept, the theory of reduction developed for the vtZ2 vibrational state by Sarka and Harder [K. Sarka, H. Harder, J. Mol. Spectrosc. 197 (1999) 254] has been extended to the vtZ3 vibrational state including terms up to H62. Owing to problems in the reproduction of data with low K and A1–A2 symmetry, two types of fits have been performed using five reduced forms of the effective Hamiltonian. The first type of fit used a reduced data set for which part of the transitions has been omitted. The unitary equivalence of the determined parameter sets has been demonstrated including newly derived relations for parameters in v10Z3. In the second type of fit, the complete data set has been included, yielding satisfactory results only in one reduction. In both type of fits, parameters up to sixth order have been determined including the axial rotational constant A and the Coriolis constant Az for both values of l. General features of the direct l-type resonance spectrum in a vtZ3 level are discussed. q 2005 Elsevier B.V. All rights reserved.