A new treatment of the v4 = 2 excited state of the symmetric top molecule PF3 around 693 cm−1

- The v4 = 2 level of the phosphorus trifluoride has been studied near 693 cm−1.
- The data were refined using five reductions of the rovibrationnal Hamiltonian.
- The unitary equivalence of parameter sets of different reductions are quite fulfilled.

All experimental data of the 2ν40 parallel and 2ν4-2 perpendicular components of the pyramidal molecule PF3 have been refined using five equivalent D-, Q-, QD-, L-, LD-reduction forms of the effective rovibrational Hamiltonian recently developed for the vt(E) = 2 vibrational state of a C3v symmetric top molecule. The v4 = 2 excited level of the PF3 molecule has been treated with models taking into account ℓ- and k-intravibrational resonances. The body of data comprised 1171 IR lines of the 2ν40 component, 249 energies of the v4 = 2−2 substate deduced from the 2ν4-2-ν4-1 hot band and 5 reported MW data. The standard deviations of the fits are practically similar for the reductions applied and close to the quality of measurements. The unitary equivalence of the tested relations between the derived parameters was satisfactorily fulfilled.