Original scientific paper

On the Vibrational Interlacing Rule in Linear and Planar Molecules

Tomislav P. Živković ; Ruđer Bošković Institute, P. O. Box 180, HR-10002 Zagreb, Croatia

Abstract

If A and Br are two molecules that differ by a single isotopic substitution, then in the harmonic approximation vibrational frequencies of molecule A are interlaced with vibrational frequencies of molecule Br This interlacing rule is a generalization of the well known order rule. The interlacing rule is particularly simple in the case of stretching and bending vibrations of linear molecules as well as in the case of out-of-plane vibrations of planar molecules. The validity of the interlacing rule for these vibrations is demonstrated with a few examples. Violation of this rule indicates either (very unlikely) strong anharmonicity effects, or (more likely) erroneous vibrational assignments. Hence, this rule can help in the analysis of vibrational spectra, in particular in the assignments of experimental frequencies to various vibrational types.

Keywords

interlacing rule; vibrational isotope effect; harmonic approximation; linear molecules; planar molecules

Hrčak ID:

131756

URI

https://hrcak.srce.hr/131756

Publication date:

4.11.2002.

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