Atomic vibronic coupling constant

An atomic vibronic coupling constant (AVCC) [33] is defined by... 

For each mode, the amplitude of the distortion corresponds to the actual displacement of oxygen atoms, 0.014 A. Then the vibronic coupling constants C were calculated from the splitting energy AE of the ground T5 level. 

The largest vibronic coupling constants are found for the eg and f2g(2) modes, while for the f2g( 1) mode it is about one order of magnitude smaller. From these data we can also estimate the JT stabilization energy per U atom, 10 cm-1 for eg, 8 cm-1 for tyjl), and only 0.5 cm-1 for 2g(l)- All these energies are smaller than the thermal energy at the transition point, TN /kH 20 cm 1. 

The atomic unit of the linear vibronic coupling constant Va is Eh/(meao) =... 

H. Koppel and R. Meiswinkel, Point-Charge Model for Vibronic Coupling Constants of Metal Atom Trimers , Z. Phys. D 32, 153 (1994). 

The description of the radiationless processes which lead to the transfer of excitation energy from one excited state to another in heavy metal complexes has been discussed by several authors (JI, 17, 22). Spin-orbit coupling must be included in the description of the initial and final states for the radiationless process but may also contribute to the coupling terms responsible for this process (II, 17). There are also vibronic coupling terms which arise from breakdown of the Bom-Oppen-heimer approximation which presumably play some role in radiationless energy transfer processes in both heavy- and light-atom molecules (II, 17). Beyond these electronic terms, there are vibrational contributions to the rate constant for a radiationless process, and these contributions are generally expressed as Franck-Condon factors (II). 

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