Coupling matrices

To solve for the Y, we begin by solving a reference problem wherein the coupling matrix is assumed diagonal with constant couplings within each step. (These could be accomplished by diagonalizing U, but it would be better to avoid this work and use the diagonal U matrix elements.) Then, in temis of the reference U (which we call Uj), we have... 

Here the distortion (diagonal) and back coupling matrix elements in the two-level equations (section B2.2.8.4) are ignored so that = exp(ik.-R) remains an imdistorted plane wave. The asymptotic solution for ij-when compared with the asymptotic boundary condition then provides the Bom elastic ( =f) or inelastic scattering amplitudes... 

The problem of branching of the wavepacket at crossing points is very old and has been treated separately by Landau and by Zener [H, 173. 174], The model problem they considered has the following diabatic coupling matrix ... 

Some final comments on the relevance of non-adiabatic coupling matrix elements to the nature of the vector potential a are in order. The above analysis of the implications of the Aharonov coupling scheme for the single-surface nuclear dynamics shows that the off-diagonal operator A provides nonzero contiibutions only via the term (n A n). There are therefore no necessary contributions to a from the non-adiabatic coupling. However, as discussed earlier, in Section IV [see Eqs. (34)-(36)] in the context of the x e Jahn-Teller model, the phase choice t / = —4>/2 coupled with the identity... 

A. The Quantization of the Non-Adiabatic Coupling Matrix Along a Closed Path... 

Hence, in order to contract extended BO approximated equations for an N-state coupled BO system that takes into account the non-adiabatic coupling terms, we have to solve N uncoupled differential equations, all related to the electronic ground state but with different eigenvalues of the non-adiabatic coupling matrix. These uncoupled equations can yield meaningful physical... 

B. The Quantization of the Three-State Non-Adiahatic Coupling Matrix... 

We concentrate on an adiabatic tri-state model in order to derive the quantization conditions to be fulfilled by the eigenvalues of the non-adiabatic coupling matrix and finally present the extended BO equation. The starting point is the 3x3 non-adiabatic coupling matrix,... 

The adiabatic coupled SE for the above 3x3 non-adiabatic coupling matrix are... 

D. Second-Derivative Coupling Matrix TIT. Adiabatic-to-Diabatic Transformation... 

These coupling matrix elements are scalars due to the presence of the scalar Laplacian V. in Eq. (25). These elements are, in general, complex but if we require the to be real they become real. The matrix unlike its... 

W (Rj.) is an n X n diabatic first-derivative coupling matrix with elements defined using the diabatic electronic basis set as... 

Requiring l/f (r qx) to be real, the matrix W (Rx) becomes real and skew-symmetiic (just like its adiabatic counterpart) with diagonal elements equal to zero. Similarly, W (Rx) is an n X u diabatic second-derivative coupling matrix with elements defined by... 

The ADT matrix U(q ) obtained in this way makes the diabatic first-derivative coupling matrix that appears in the diabatic Schrodinger... 

Since the second-derivative coupling matrix is only an additive teiin in Eq. (87), we can merge it with the diabatic energy matrix and define a 2 x 2 diabatic matrix... 

LHSFs are determined at the center p of each shell. These LHSFs are then used to obtain the coupling matrix p) given in Eq. (102). The coupled... 

The matrix of vectors F is thus the defining quantity, and is called the non-adiabatic coupling matrix. It gives the strength (and direction) of the coupling between the nuclear functions associated with the adiabatic electronic states. 

The elements of the matrix G can be written in terms of F, which is called the non-adiabatic coupling matrix. For a particular coordinate, a, and dropping the subscript for clarity,... 

Thus, as the adiabatic PES become degenerate the adiabatic coupling matrix elements become singular. 

The direction of X2 is parallel to the direction g of the diabatic coupling matrix mentioned above... 

One of the main outcomes of the analysis so far is that the topological matrix D, presented in Eq. (38), is identical to an adiabatic-to-diabatic transformation matrix calculated at the end point of a closed contour. From Eq. (38), it is noticed that D does not depend on any particular point along the contour but on the contour itself. Since the integration is carried out over the non-adiabatic coupling matrix, x, and since D has to be a diagonal matrix with numbers of norm 1 for any contour in configuration space, these two facts impose severe restrictions on the non-adiabatic coupling terms. 

In this section, we intend to show that for a certain type of models the above imposed restrictions become the ordinary well-known Bohr-Sommerfeld quantization conditions [82]. For this purpose, we consider the following non-adiabatic coupling matrix x ... 

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