Term: Renner–Teller effect
https://doi.org/10.1351/goldbook.R05290

Definition:
Molecular distortion in linear molecular species with degenerate electronic states (e.g. belonging to the C∞v group). The Renner–Teller effect is a particular case of the Jahn–Teller effect. From the point of view of the potential energy surfaces the Renner–Teller effect generates a surface touching (see scheme below).

Notes:
0) The Renner–Teller effect arises from splittings in the vibrational levels of molecular entities due to even terms in the vibronic perturbation expansion. This is generally a minor effect for non-linear molecular entities compared to the @J03361@, which is due to the odd terms.
1) For linear molecular entities it is the only possible vibronic effect characteristic of degenerate electronic states. R05290.png

Related Terms:
1) jahn–teller effect (http://doi.org/10.1351/goldbook.J03361).

Image: Renner–Teller effect diagram (https://goldbook.iupac.org/img/inline/R05290.png) 

Source: PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 414 (https://doi.org/10.1351/pac200779030293)

Citation: 'Renner–Teller effect' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.R05290

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