Curve Crossing Problem with Arbitrary Coupling: Analytically Solvable   Model
  We give a general method for finding an exact analytical solution for the two state curve crossing problem. The solution requires the knowledge of the Green's function for the motion on the uncoupled potential. We use the method to find the solution of the problem in the case of parabolic potentials coupled by Gaussian interaction. Our method is applied to this model system to calculate the effect of curve crossing on electronic absorption spectrum and resonance Raman excitation profile. 
Aniruddha Chakraborty
quant-ph physics.chem-ph