Pitzer mode

In addition, an out-of-plane skeletal mode can be active whose frequency is given by [Pitzer (774)]... 

Our results add little to the question of the structure of ihe xenon hexafluoride molecule. The polarized Raman line al 621 cm could be assigned to the v, (a,) stretch of an octahedral molecule, and the depolarized line at 508 cm to V2 e,) the intensity pattern (v2 is comparable with i/ ) is very reminiscent of the Raman spectra of some isoelectronic molecules which are octahedral, viz. the hexahalogenotellurates(lV). Octahedral symmetry, however, cannot be reconciled with the complicated infrared spectrum of XeFs vapor, at least in the approximation of a simple harmonic force field. Pitzer and Bernstein have in any case provided persuasive evidence for XeFj monomer being substantially distorted in the Ti. bending mode from octahedral symmetry. This is in essential agreement with the bonding model proposed by Bartell and Gavin. ... 

The hindered rotor is a hybrid between a free rotor and a vibration. An example of this important mode is the methyl group rotation in such molecules as ethane, acetaldehyde, and toluene. The potential for such a mode in lowest order is given by (Pitzer, 1953) ... 

Statistical Thermodynamics of Bond Torsional Modes. Tests of Separable, Almost-Separable, and Improved Pitzer-Gwinn Approximations. 

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