Reinvestigation of The 24(A, E) Infrared Band of Phosphorus Trifluoride

The v4 = 2 0 and v4 = 2 -2 excited states of the oblate molecule PF3, lying near 693 cm -1 , were reinvestigated by highresolution FTIR spectroscopy. Assumed to be isolated, these levels were treated by applying different reduction forms of the effective rovibrational Hamiltonian recently developed for the vt(E) = 2 vibrational state of a C3v symmetric top molecule, with models taking into account l- and k-type intravibrational resonances. Parameters up to sixth order have been accurately determined. The unitary equivalence of the derived parameter sets in different reductions was successfully verified.