Potential energy, distortion from vibronic

To examine the potential energy distortion and displacement arising from the nn -nn vibronic coupling, we consider two electronic states m(q, Qn)) and n(q, Q0)), which are eigenfunctions of the electronic Hamiltonian (HJ ... 

Figure 6. Schematic representation the potential energy distortion resulting from the vibronic interaction between two close-lying excited states. The dashed curves represent the potential energy curves in the absence of vibronic coupling. (From ref. [21] with permission.)...

Fig. 1 The adiabatic potential surface of an electronic Eg state due to the linear vibronic interaction with a vibrational mode top) the mexican hat-shaped curve on the left is modified by higher order coupling terms, yielding a three minima-refinement, which is shown in a cross section perpendicular to the energy axes on the right. The potential surface, resulting from Tg Eg coupling (amidst), leads to an analogous three-well-structure already in first order - each of these corresponding to a tetragonal polyhedron distortion along one of the three molecular axes. The vibrational ai and e modes are shown on the bottom (adopted from [2])...

Fig. 2. Vibronic E e JT spectra for two different values of Eyp, Eq. (6). The electronic transition is from a nondegenerate, JT-undistorted state to the JT-distorted final state as indicated schematically in the lowest panel of the figure. Here the Mexican hat potential energy surfaces are represented roughly by the double cone, with the upper-cone vibrational levels indicated by the three straight lines (for Ejt = 400ta).

---