Pseudo-Jahn-Teller problem

Pseudo Jahn-Teller Problem of Mossbauer Spectra of Charge-Ordered Biferrocenium Crystals Coexistence of Localized and Delocalized States... 

Pseudo -Jahn-Teller Problem of the Photochromic Compounds... 

The shape resonances of benzene and some of its derivatives have been explored by a number of investigators using ETS (16,17,20, 36). With the exception of questions regarding pseudo-Jahn-Teller problems (37), for example in the alkyl-benzenes, substituent effects on the doubly-degenerate ground state anion near 1.1 eV... 

Fig. 1. The adiabatic potentials (AP) in the Jahn-Teller (a), Renner-Teller (b), and pseudo-Jahn-Teller (c) effects for systems with a double degenerate electronic term interacting with one coordinate Q (E bi problem in the JT case). In all three cases the ground state is unstable in the high-symmetry configuration <2 = 0, while the stable configurations at Q0 are at lower symmetry. The differences between these cases are in the behavior of the AP at Q = 0.

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... 

Hamiltonians formally similar to Eq. (2.4) are encountered not only in the central problems of lattice dynamics and electron propagation, but also in a large variety of other problems. Among them we mention the Frenkel theory of excitons, the coupled electron-lattice impurities in the entire range of coupling, the Jahn-Teller (or pseudo-Jahn-Teller) systems, interacting spins, and so on. 

In other cases there may be three equivalent minima of dipolar type on the adiabatic potential, e.g., in the cases of molecules with D3h symmetry. Such an adiabatic potential can be due to either the pseudo-Jahn-Teller effect or the Jahn-Teller effect in the case of twofold degenerate electronic terms with quadratic terms of the vibronic interactions included (the quadratic E (g) e problem). If the dipolar minima are deep enough and only the tunneling states are populated, then 7/Vibr and the operator of dipole moment can be expressed by matrices of the dimension 3x3 ... 

Piepho has treated intervalence transitions using a relatively simple three-center molecular orbital model in which vibronic coupling is introduced as a pseudo-Jahn-Teller perturbation. This could be a valuable approach, and it can probably be generalized to a great variety of problems. In this report, Piepho uses the approach to calculate intervalence transition band shapes for a range of vibronic couplings, and she discusses the vibronic criteria for valence trapped and delocalized systems. 

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. ... 

B. Bersuker, Pseudo Jahn-Teller origin of perovskite multiferroics, magnetic-ferroelectric crossover, and magnetoelectric effects. The d -d problem, Phys. Rev. Lett., 108, 137202 (2012). 

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