ChemInform Abstract: High‐Resolution FTIR Investigation of PF3 in the 300‐550 cm‐1 Region: The Ground, ν2 = 1, and ν4 = 1 States.

Abstract

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A new analysis of the ν4(E) rovibrational band of the symmetric top molecule PF3

“…The J-dependent parameters up to sextic centrifugal distortion constants, and including a very small h 3 splitting term, have been determined by Cotti et al [2] using MW and RF spectra. The experimental C 0 value has been obtained by Najib et al [1] from effects associated with avoided crossings within the v 4 = 1 state. However, the D 0 K constant comes from harmonic force field [26], while H 0 K remains unknown.…”

“…The predictions were based on our previous results [1] and rotational transitions recently measured in the centimetre-wave (MW), millimeter-wave (MM) and radiofrequency-wave (RF) ranges [7]. About 590 new transitions of the m 4 perpendicular band were identified with K max /J max = 66/67.…”

“…In our previous study of the lowest m 4 fundamental band of PF 3 near 347 cm À1 [1], by high-resolution infrared spectroscopy (a resolution of 3 Â 10 À3 cm À1 ; the accuracy of the wavenumber scale ca. 2 Â 10 À4 cm À1 ), it was found that the v 4 = 1 state is well isolated, but affected by numerous intravibrational perturbations.…”

“…The main objective is first to extend the assignment of m 4 transitions to high values of the rotational quantum numbers J and K in the our previous FTIR spectrum [1], and second to check the validity of the approach of unitary equivalent sets of parameters in different reductions of the rovibrational Hamiltonian H. Since the sphericity of the oblate molecule PF 3 is not too pronounced, c = 2(jC 0 À B 0 j)/(C 0 + B 0 ) = 0.479, the various reduced forms of H can be applied.…”

“…It has four vibrational normal modes: two non-degenerate A 1 -type modes: m 1 and m 2 ; two degenerate E-type modes: m 3 and m 4 . PF 3 was the subject of several studies by rotational and vibrational spectroscopy [1][2][3][4][5][6][7][8][9]. The more recent ones can be summarised as:…”