Molecular structures pseudo-Jahn-Teller effect

The strategy of vibronic analysis is to regard the molecular skeleton in the higher possible symmetry, analyzing the forces distorting or keeping this structure. In case of distortion, a Jahn-Teller (JT) or pseudo Jahn-Teller effect (PJT) takes place. Even in the absence of distortion, a vibronic part exists inside of force constants of each normal vibration mode and its analysis could offer particular insight into molecular structure. 

The evidence for the molecular structure of XeP has been reviewed by Pitzer and Bernstein they concluded that there is no reason to question the proposal that the structure arises from a pseudo-Jahn-Teller effect associated with the relatively low energy of excitation of a 5s electron to a 5p level. 

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