Electronic shielding by closed shells in thulium compounds

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The Mossbauer effect has been used to investigate electronic shielding by closed electron shells in salts of trivalent thulium, by measuring the temperature dependence of the nuclear quadrupole splitting of the 8.42 keV gamma transition in Tm[superscript 169]. The nuclear quadrupole interaction was studied for Tm[superscript 3+] ions in thulium ethyl sulfate, thulium oxide and thulium trifluoride within a temperature range from 9.6?K to 1970?K. The interpretation of the experimental data in terms of the contributions of distorted closed electron shells to the quadrupole interaction yields values for electronic shielding factors. The results lead to amounts of 10% or less for the atomic Sternheimer factor R[subscript Q]. The experiments also reveal substantial shielding of the 4f electrons from the crystal electric field, expressed by the shielding factor [sigma][subscript 2]. Values of 250 and 128 are obtained for the ratio [...] for thulium ethyl sulfate and thulium oxide respectively, where [...] is the lattice Sternheimer factor