Pseudo Jahn-Teller coupling

Tunneling splitting in a two-level system with pseudo-Jahn-Teller coupling 66... 

TUNNELING SPLITTING IN A TWO-LEVEL SYSTEM WITH PSEUDO-JAHN-TELLER COUPLING... 

A parameterization method of the Hamiltonian for two electronic states which couple via nuclear distortions (vibronic coupling), based on density functional theory (DFT) and Slaters transition state method, is presented and applied to the pseudo-Jahn-Teller coupling problem in molecules with an s2-lone pair. The diagonal and off-diagonal energies of the 2X2 Hamiltonian matrix have been calculated as a function of the symmetry breaking angular distortion modes and r (Td)] of molecules with the coordination number CN = 3... 

Our work on this very interesting system is still in progress, and we hope to include more electronic states it is clear that the E and T states can pseudo-Jahn-Teller couple to each other via t vibrations. Given the Jahn-Teller active t2 vibrations discussed above and the fact that the E and T states are very close in energy one would expect these states to strongly pseudo-Jahn-Teller couple. The Jahn-Teller effects in singlet tetrahedral Fe(CO)4 are probably similar to those in the P4+ cation (combined Jahn-Teller and pseudo-Jahn-Teller action... 

Trihalide cations MFs", MCl3 and MBrJ, M = B, Al, Ga pseudo Jahn-Teller coupling, electronic spectra and ionization potentials... 

Simple examples of these effects were discussed in Section IV as limiting cases of the pseudo-Jahn Teller and pseudo-Renner-Teller effects. There it was shown that instead of using the adiabatic approximation, we should, in the interest of convenience, adopt a diabatic approximation in which the electronic degeneracy is maintained in zeroth order. The splitting can then simply be ascribed to adiabatic coupling proportional to Q, (or Qf, etc.) or to Qf (or Qf, etc.) between the two electronic components that remain degenerate at Q, = 0. The selection rule for pseudo-Jahn Teller coupling is thus <0° 0 or, iff denotes representation, T , x F,- x F 3-4,. 

Apart from coupling the two components of a degenerate ( -type) electronic state, they may also be involved in Herzberg-Teller (pseudo-Jahn-Teller) coupling of the E state with a nondegenerate (.4- or B-type) state. If the ground state totally symmetric (i4i), the final state Oj m) can have the following symmetries ... 

Here we consider the case that the two excited electronic states <1> and belong to dipole-allowed representations, namely, one to A2 and the other to E, (Zgierski and Pawlikowski, 1979b). In the absence of pseudo-Jahn-Teller coupling between them, the corresponding vibronic wave-functions are of the form... 

In general, interference between (weak) Jahn-Teller and pseudo-Jahn-Teller couplings in D4 molecules manifests itself only in the relative cross sections of 0-0 and 0-1 bands in the fundamental REPs of the and bj bands. Their ratio is thus not only a measure of the nonadiabatic coupling in this case. The magnitude of the interference contribution depends on the relative magnitude of the k and A coefficients for these modes. 

The observation of a strongly enhanced Vio(eig) fundamental and its first overtone has been interpreted (Ito et ai, 1978) as due to pseudo-Jahn-Teller coupling between Ei and a A2 (tr,7c ) state, which thus far has been located only tentatively, namely, at somewhat higher energies than predicted by the analysis. There is good supporting evidence to indicate that the assignment is correct, which in turn helps to locate the new electronic state. 

A later study added the pseudo-Jahn-Teller coupling to the B B2 state to this model. This resulted in a 10-mode model, the spectrum of which is shown in Fig. 5(b). The two parts of the spectrum are plotted separately to show that the peaks at either end can be assigned to each state, with the overlap in the middle forming a structureless band. 

Simulations of femtosecond time-resolved photoelectron spectra have first been performed with this formalism for a three-mode model of the S1-S2 conical intersection in pyrazine (see below). With the same technique, Schon and Koppel have explored the real-time detection of pseudo-rotational motion due to Jahn-Teller and pseudo-Jahn-Teller couplings in Na3. The same problem has been addressed within the perturbational formalism by Dobbyn and Hutson.Charron and Suzor-Weiner have treated the femtosecond photoionization dynamics of Nal within the non-perturbative approach, considering also passive control scenarios to influence the fragmentation pattern of Nal. ... 

L. Blancafort, M. J. Bearpark, and M. A. Robb, Ring puckering of cyclooctatetraene and cyclohexane is induced by pseudo-Jahn-Teller coupling. Mol. Phys. 104, 2007-2010 (2006). 

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