Nonadiabatic effects coupling terms

The off-diagonal operators q, with eVe, couple the electronic states and give rise to nonadiabatic effects which can strongly affect the molecular properties. The second-order perturbation theory shows that these couplings can be neglected with respect to the diagonal BO terms of Eqs. (2.3) when... 

The solid lines represent the cross sections calculated within the theoretical fiumewoik indicated in tide previous section. For the fit a Morse-Spline-van der Waals model function for Vq(R) and a Buckingham-Comer model function for V2(R) have been used. The six adiabatic effective potential curves obtained are shown in Figs. 6,7,8,9,10 for 0-Ar,Kr,Xe,CH4, and E>2 respectively, together with nonadiabatic coupling terms. Relevant potential parameters for the above interactions are reported in Table 1. 

In order to make direct comparison with experimental spectra, the motions of the nuclei, in particular vibrations, have also to be considered this is done according to equation (4), in which case Xn refers to vibrational wavefunctions. Rotational effects are also computed on the basis of equation (4). If the. so-called nonadiabatic coupling terms involving electronic states... 

The first three terms on the right-hand side correspond to the Marcus relation for the nonadiabatic case where there is no coupling between the diabatic energy states (i.e. E = 0 at all values of the reaction coordinate). The fourth and fifth terms reflect the effect of the adiabatic coupling of the two surfaces on the transition state and reactant state, respectively, and < /2 AGjxn + 4AGin,l. ... 

We explain these nonadiabatic coupling effects of coherently excited quasidegenerate electronic states in terms of a simplified one-dimensional model analysis. 

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