The isomeric chemical shifts (IS) of the Mossbauer 37.2 keV y-line of the Sb121 nucleus in organic compounds of antimony (type Ar,SbX,, Ar4SbX, and Ar,Sb) have been measured. The spectra of the resonance absorption are mainly found to be broadened single lines with appreciable asymmetry. The results obtained are interpreted on the basis of the semi-empirical method of hybrid orbitals.Die isomeren chemischen Verschiebungen (IS) der 37,2 keV-y-Linie des SblZ1-Kerns wurden in organischen Antimonverbindungen (des Typs Ar,SbX,, Ar,SbX und Ar,Sb) gemessen. Die Resonanzabsorptionsspektren sind hauptsiichlich verbreiterte Einzellinien mit betriichtlicher Asymmetrie. Die erhaltenen Ergebnisse werden auf der Grundlage der halbempirischen Methode der Hybridbahnen erklirt. This report presents investigations of isomeric chemical shifts (IS) of the MOSS-bauer y-line with an energy of 37.2 keV of theSb121 nucleus in the antimonyorganic compounds of the type Ar3SbX,, Ar,SbX, and Ar3Sb (Ar = C,H,, CH30C6H,, C1C6H,; X = F, C1, Br, BF,).The spectra of resonance absorption were measured using an electrodynamic vibrator providing a constant velocity. The measurements were carried out at liquid nitrogen temperature.The resonance y-radiation was detected using a photomultiplier @3Y-37 with NaI (Tl) crystal of 0.3 mm thickness across the escape peak of 37.2 keV y-quanta.The SblZ1 nuclei in the Sn12102 lattice were the source of y-quanta [l]. The spectrum of y-quanta resonance absorption in InSb gives a single line having the width rexp = (2.8 & 0.2) mm/s which is slightly above the natural width of the line (2 r = 2.1 mmls). The observed broadening of the line is due to the finite thickness of the absorber (9 mg/cmz of SblZ1). All the studied compounds were synthetized from antimony containing the naturally occuring isotope Sbla1.

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The Mossbauer effect of the 35.5 keV transition in TelZ5 has been studied in Mei[Te1VHa16] type compounds. The dependence of the isomeric shift on ligand electronegativity has been found to disagree with the behaviour expected from the positive sign of A R / R established for Te125. Such disagreement can be explained by the presence of an unshared pair of electrons on the valence shell of the four-valent tellurium in the compounds studied. The spectra of the resonance absorption of the 35.5 keV y-transition in Te125 for hexa-coordination tellurium compounds of the Me,[TeHal,] type were measured. The absorbers used by us were enriched up to 96% with Te125. The measurements were carried out a t liquid nitrogen temperature using a multichannel installation which operated a t uniform variable speed . I n some cases measurements were made using an installation with constant speed. Radioactive SblZ5(Cu) and Te1250, sources were used. For convenience sake all values of 6E listed in Table 1 were related to ZnTe. The resonance y-radiation was detected using a scintillation counter with a NaI(T1) crystal of 0.1 mm thickness with the aid of the escape peak of the 35.5 keV y-quanta. All compounds studied, except for [TeFJ-, exhibited the absorption spectra in the form of a singleline with linewidth close to the natural one (5.4 to 5.6 mmjs). In the case of [TeF6l2-a quadrupole splitting A E = (5.6 & 0.1) mm/s was observed (Fig. 1). Fig. 2a shows the dependence 6E(Ax) in the compounds studied.

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