Conical intersections Renner-Teller effect

Yang-Mills fields, 249-250, 255-257 Lagrangian multiplier, conical intersection location, 488-489, 565 Laguerre polynomials, Renner-Teller effect, triatomic molecules, 589—598 Lanczos reduction ... 

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. 

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