Sternheimer nuclear shielding

Quantum mechanical calculations of 33S nuclear quadrupole coupling constants are not an easy matter (not only for the 33S nucleus, but for all quadrupolar nuclei). Indeed, the electric field gradient is a typical core property, and it is difficult to find wave functions correctly describing the electronic distribution in close proximity to the nucleus. Moreover, in the case of 33S, the real importance of the Sternheimer shielding contribution has not been completely assessed, and in any case the Sternheimer effect is difficult to calculate. 

AR = change in nuclear radius Rq, -Roe = Sternheimer shielding factors Rfim =distancefrommthtonthion n = radial coordinate of ith electron rtj = distance from ith to /th nucleus [Pg.389]

The nuclear electric quadrupole moment may also interact with the electric field gradient arising from the non-spherical distribution of the 4f electrons when the lanthanide ion is situated in a solid. The general form of the quadrupole interaction has been given in section 1.3.2. The principal value of the field gradient tensor, due to the 4f electrons is given by (18.73) in section 2.1.1.2, and as indicated there in (18.72) should be multiplied by the Sternheimer shielding factor (I-Rq) to take account of the distortion of the inner closed shells of the lanthanide ion by the open 4f shell. Other contributions to the total... 

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