The two lowest electronic states (arising from X2Π u) are treated analytically with inclusion of excited state effects in a slightly bent Renner-Teller acetylene molecular ion. The aim is to explain the anomalous values of approximately π for the integrated non-adiabatic coupling term (NACT), recently obtained by ab initio calculations, as, e.g., in Halsz et al (2007 J. Chem. Phys. 126 154309). These occur when the molecular path twice coincides with symmetrically placed positions of degeneracies (conical intersections). However, the admixture of excited states into X 2Πu removes these coincidences, creates two aligned conical intersections in a planar arrangement and perturbationally reduces the integrated NACT from its value of π.
|Journal||Journal of Physics B: Atomic, Molecular and Optical Physics|
|Publication status||Published - Jan 28 2008|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics