Radiofrequency, centimeter-, millimeter- and submillimeterwave spectra of PF3 in the v4=1 vibrational state

Abstract

Rotational spectra of PF3 in the degenerate vibrational state v4=1 have been measured in the radiofrequency, centimeter-, millimeter- and submillimeterwave range. 157 rotational transitions obeying the selection rules ΔJ=1, Δk=Δl=0 have been observed in the range 100–900GHz for 9≤J≤57 and 0≤k≤37. The J=1←0 transition and 246 direct l-type resonance transitions (Δl=Δk=±2) with values of J from 16 to 75 and G=|k−l| up to 74 have been measured using waveguide microwave Fourier transform spectroscopy in the range 8–26.5GHz. Due to an accidental degeneracy of the kl=−1 and 2 levels it was possible to observe for J=17and18 Δ(k−l)=3 ‘perturbation-allowed’ transitions with selection rules kl=0←−1 and kl=2←3. In addition, A1–A2 splittings with kl=−2and4 have been measured for J=25–29 in the radiofrequency range using the technique of two-dimensional radiofrequency–microwave double-resonance Fourier transform spectroscopy. The data were analysed using the three reduced forms of the effective Hamiltonian [E.I. Lobodenko et al., J. Mol. Spectrosc. 126 (1987) 159; H. Harder, J. Mol. Spectrosc. 194 (1999) 145]. Parameters up to seventh order are accurately determined and the unitary equivalence of the three parameter sets is demonstrated.