Heavy atoms, inducing spin-orbit

G. Kavarnos, T. Cole, P. Scribe, J. C. Dalton, N. J. Turro, Molecular photochemistry. XXXIX. External heavy-atom-induced spin-orbital coupling. Spectroscopic study of naphthonorbom-anes, J. Am. Chem. Soc., 1971, 93, 1032-1034. 

Another very important factor that should be considered is the expected large spin-orbit effect promoted by a heavy atom as gold. The heavy-metal-induced spin-orbit coupling favors an effective emission from the triplet excited states that leads to a phosphorescence, which generally is not observed for linear molecules.27... 

In this section the effect of spin-orbit coupling on radiative and radiationless intercombinational transitions (transitions occurring between states of different multiplicity) will be investigated. We will be particularly concerned with the use of internal and external heavy atoms to induce spin-orbit coupling. The effect of heavy atoms on intercombinational processes occurring in aromatic hydrocarbons, carbonyl compounds, and heterocyclic compounds will be discussed. 

Kaupp, M., Malkina, O.L., Malkin, V.G. and Pyykkd, P. (1998) How do spin-orbit induced heavy-atom effects on NMR chemical shifts function Validation of a simple analogy to spin-spin coupling by DFT calculations on some iodo compounds. Chemistry - A European Journal, 4, 118-126. 

However, the Ne(2s2) state has some triplet character due to mixing with Ne(2s4). It is of considerable interest to investigate the restrictive effect of an overall spin-change in any electronic process. It has been noted that, of the inert gases, only Xe induces collisional deactivation of 0(2 lD) to 0(2 3P), which may be due either to chemical interaction, or to the spin-orbit coupling in the heavy atom. Most gases will induce the spin forbidden transition... 

Heavy atom effects on the decay dynamics of triplet state ion pairs have been studied in chloranil-naphthalene 1 2 termolecular systems. The triplet exciplexes and radical pairs involved in geminate recombination which occurs with the methylene blue triplet and p-iodoaniline have been examined for spin-orbit coupling induced magnetic field effects . 

More subtle are the spin-orbit-induced heavy-atom chemical shifts at the atom nearest to the heavy one, or at more remote nuclei. If one uses the same Hamiltonians as Ramsey, one must go to third-order perturbation theory, with one Zeeman, one hyperfine, and one spin-orbit matrix element [22]. For a recent discussion on the nature of this shift, see Ref. [23]. It was also noted that an analogous effect, a heavy-atom shift on the heavy atom can occur, for instance on the Pb(II) nucleus in PbR compounds. The early semiempirical calculations suggested that the Zeeman-SO-Fermi contact cross term, zero in Ramsey s theory, could then become the dominant contribution to the Pb chemical shift [24]. 

A part of the relativistic corrections due to a heavy neighboring atom can be approximated by third-order perturbation theory with nonrelativistic functions. The contribution to shielding comes from the cross term involving the spin-orbit coupling, I S interaction, and the external field-orbit interaction. In nonrelativistic terms, the shielding mechanism is that the external field induces an orbital angular momentum on the electrons of the heavy atom (Br or I), this produces a polarization in the electron spin by spin-orbit coupling, and the spin polarization is transferred to the resonant nucleus by a Fermi contact and by a nuclear spin-electron spin dipolar... 

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