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

Abstract All experimental data of the 2 ν 4 0 parallel and 2 ν 4 - 2 perpendicular components of the pyramidal molecule PF 3 have been refined using five equivalent D -, Q -, QD -, L -, LD -reduction forms of the effective rovibrational Hamiltonian recently developed for the v t ( E ) = 2 vibrational state of a C 3v symmetric top molecule. The v 4  = 2 excited level of the PF 3 molecule has been treated with models taking into account l - and k -intravibrational resonances. The body of data comprised 1171 IR lines of the 2 ν 4 0 component, 249 energies of the v 4  = 2 −2 substate deduced from the 2 ν 4 - 2 - ν 4 - 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.