Vibronic orbital

THE ORBITAL APPROACH TO PSEUDO JAHN-TELLER EFFECT. A NEW CONCEPT THE VIBRONIC ORBITALS... 

Here we will focus our attention in developing a new concept related to the orbital paradigm in vibronic analysis, proposing new objects named vibronic orbitals. The general formula (5) and the application in Section 4 shows that in spite of the crude belief that the contributing elements can be limited to the frontier orbitals, the... 

The vibronic orbitals are interesting new objects having properties recommending them for further use and investigation. Namely,... 

In order to recover the conceptual simplicity of the (a + a") <8> A effect at planar ammonia we will call now the newly introduced vibronic orbitals. With this tool one may find indeed single pair of occupied (u j-virtuaKuj) functions that carry a 93.5% from the total of vibronic curvature. The remaining part is coming from vibronic orbitals spanning other symmetry channels, e.g. occupied(a,l)-virtual(a"). The symmetry distribution of different ordered product representation to the total vibronic curvature is given in Table 2a and the total balance of vibronic and nonvibronic terms, in Table 2b. 

Table 2a. The negative curvature components, in terms of vibronic orbitals...

To be distinguished from previous case, Table 3 shows that the HOMO-LUMO pair exerts visible predominance among the many other small orbital promotions. Correspondingly, the vibronic orbitals are similar to the frontier orbitals (Fig. 3). A nontrivial conclusion drawn from the weight of contributions in terms of vibronic... 

Fig. 2. The canonical frontier MOs and vibronic orbitals of NH3 molecule considered as (flj + effect in Dih reference, (a) The d HOMO, coincident by symmetry reasons...

Fig. 3. The canonical frontier MOs and vibronic orbitals of C1F3 molecule considered as ( + ef) E effect in D3h reference, (a) The a HOMO (b) and (c) the degenerate e LUMO (d) the a occupied vibronic orbital, (e) and (f) the e virtual vibronic orbitals. Note the closeness between vibronic orbitals and the frontier ones in this case.

With respect to the D2h group of delocalized system, the PJT coordinate has a Blu representation. The vibronic orbital terms are spread over many small... 

Fig. 5. The vibronic orbitals describing the main part of electron structure change when turning from delocalized to localized mixed valence in hypothetical molecule [A12C16]2. ...

Fig. 6.3 Ring closure of di-butadiene to cyc/o-butene. In C2v symmetry there is a symmetry mismatch between the 2 and a occupied orbitals. Vibronic orbited coupling requires a concerted mechanism, based on a conrotatory ting closure, which conserves only the C2 axis...

---