Spin orbit splitting, Jahn-Teller

Figure 10. Term splitting diagrams for the Cu(II) ion in a C3, site with Jahn-Teller and spin orbit splitting and band assignments for experimentally observed transitions (Figure 9b) drawn to scale.

Discussion. Copper in Krypton. The absorption spectra of copper atoms Isolated in rare gas matrices have been extensively studied (15-25) and the triplet of bands at 310nm attributed to a number of different causes. These include (1) spin orbit splitting and static axial site distortion (17), (2) multiple matrix sites (18), (3) exciplex formation between the metal and a single matrix atom (19), (4) long range metal-metal interactions (2 ), and (5) Jahn-Teller (JT) effect resulting from matrix cage atom vibrations on the excited metal (21,22,23). The MCD of Cu atoms in the rare gas matrices has recently been reported (24,25) and the results interpreted as consistent with either the distorted site or JT hypotheses (39). 

N. E. Gruhn and D. L. Lichtenberger, in Encyclopedia of Mass Spectrometry , ed. P. Armentrout, Volume Editor, eds. M. L. Gross and R. Caprioli, Editors-in-Chief, Elsevier, 2003, Vol. 1, p. 818. Discusses the use of photoelectron spectroscopy to analyze ion states of inorganic molecules, specifically considering the influences of spin-orbit, Jahn-Teller, and exchange splitting. 

The CH3S(X ) state is subjected to the Jahn-Teller distortion, and the actual structure for CH3S(X) is expected to have a symmetry [65]. The previous studies, however, indicate that the Jahn-Teller stabilization is small [123] and is substantially smaller than the spin-orbit splitting (259 cm ) [124] for CH3S(X 3/2,i/2) In a lower C, symmetry, transforms as a and the e orbitals are split into orbitals transformed as a and a". The CH3S(X ) ground state has the electronic configuration... 

Moreover, the state is in principle Jahn-Teller unstable, and any such distortion can lead to partial quenching of spin-orbit splittings [28]. 

G. D. Bent, G. F. Adams, R. J. Bartlett, and G. D. Purvis, Many-body perturbation theory electronic structure calculations for the methoxy radical. I. Determination of Jahn-Teller energy surfaces, spin-orbit splitting, and Zeeman effect, manuscript submitted. 

Liehr has shown (142) that the orbital degeneracy of the ground state in a tetrahedral nickel(II) complex may be lifted by spin-orbit coupling. This means that these complexes may not be liable to Jahn-Teller distortion as has been thought for some time. Such coupling would also have the effect of splitting all transitions into several components, the exact number... 

There remains the possibility of g-values which depart substantially from 2.00 but are isotropic because of cubic symmetry. In practice such conditions are rare for transition metal complexes, as the Jahn-Teller theorem ensures departure from cubic symmetry in the electronic structure. However, for the lanthanoid and actinoid elements, where the spin—orbit coupling constant is very much larger than kT, the Jahn—Teller theorem may not be relevant and effective cubic symmetry certain. For the lanthanoids, g-values often depart considerably from 2.00, although some anisotropy arising from ligand field splittings is common. For the actinoids, direct observation of ESR is less common but there is evidence of a similar situation. 

The C3V symmetry at the SI site imposes on the Cu ion term splitting (21) shown in Fig. 10. The relative separations A2 between the E-states and A3 between the lower E-state and the A-state depend on the angle between the Cu-0 bond and the threefold symmetry axis (22) and, conversely, from measured A2 and A3 one can determine 3. The E-states are split further by the Jahn-Teller effect and spin orbit coupling into E+ and E components, the energies of which are given by (21)... 

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