Electronic states Renner-Teller effects

Appendix A Perturbative Handling of the Renner—Teller Effect and Spin-Orbit Coupling in n Electronic States of Tetraatomic Molecules... 

APPENDIX A PERTURBATIVE HANDLING OF THE RENNER-TELLER EFFECT AND SPIN-ORBIT COUPLING IN n ELECTRONIC STATES OF TETRAATOMIC MOLECULES... 

Hamiltonian equations, 627-628 perturbative handling, 641-646 II electronic states, 631-633 vibronic coupling, 630-631 ABC bond angle, Renner-Teller effect, triatomic molecules, 611-615 ABCD bond angle, Renner-Teller effect, tetraatomic molecules, 626-628 perturbative handling, 641-646 II electronic states, 634-640 vibronic coupling, 630-631 Abelian theory, molecular systems, Yang-Mills fields ... 

DCCS radical, Renner-Teller effect, tetraatomic molecules, n electronic states, 633—640 Degenerate states ... 

HCCS radical, Renner-Teller effect, tetraatomic molecules, II electronic states, 633-640 H2D molecule, non-adiabatic coupling, two-state molecular system, 107-109 HD2 molecule, permutational symmetry isotopomers, 713-717 potential energy surfaces, 692-694 Heaviside function ... 

There is a clear distinction between conically intersecting surfaces and two surfaces which touch, as in the so-called Renner-Teller effect for the degenerate states of linear molecules 142,43 (Fig. 7). For such a situation the electronic wave function is single valued and although there may be strong mixing between Born-Oppenheimer terms, one such term can always be taken as a first approximation to any state. 

Linear molecules are the only exception to the Jahn-Teller effect. But linear molecules may also have instabilities in their degenerate electronic states and this is called the Renner-Teller effect. It was first described by Renner in a theoretical paper on the degenerate first excited electronic state of carbon dioxide [86], It took more than twenty years to find the first experimental evidence of this effect, in the electronic absorption spectrum of the NH2 radical [87], The NH2 radical has one electron on an orbital and thus a n electronic state... 

And, Indeed, Renner-Teller distortion has been observed in many trlatomic molecules formed from a parent ir electronic state (30, 32) but only one report has been published of a substantial Renner-Teller effect in a A state (33). 

---