Makoto Yanaga

Calibration of the isomer shift of125Te from internal conversion and mössbauer measurement

Radioactive125I was ion-implanted into 7 different metal matrices. Al, Au, In, Pt, Sn, Te and Zn, and internal conversion and Mössbauer spectra associated with the 35.46 keV M1 transition of125Te were measured for the same samples. A value ΔR/R=(0.853±0.115)×10−4 was derived for the relative difference of the nuclear charge radius for the 35.46 keV M1 transition of125Te.

Calibration of the isomer shift of121Sb and119Sn by means of Mössbauer spectroscopy and molecular orbital calculation

The relationship between the isomer shifts in Mössbauer spectroscopy and the electron contact densities has been investigated for several antimony and tin compounds. Mössbauer spectra for121Sb in rapidly frozen solutions of antimony compounds were measured. The isomer shifts are compared with the valence electron densities at the antimony nucleus calculated with theab initio molecular orbital method. The relative difference of the nuclear charge radius ΔR/R could be obtained as ΔR/R =−(10.2±1.0)×10−4 for the 37.15 keV M1 transition of121Sb. Further, some computations of the electron density at the tin nucleus for several tin compounds were performed. By comparing the valence electron contact densities with isomer shifts, which had been reported for several tin compounds in rare-gas matrix states, the value of ΔR/R for 23.87 keV M1 transition in119Sn was estimated to be (1.57±0.03)×10−4.

156Dy as an activable yield tracer for determination of rare earth elements in biological materials by neutron activation analysis

Use of an enriched156Dy isotope as an activable yield tracer for the determination of lanthanoid contents in various biological reference materials has been proposed. The method consists of preconcentration of the lanthanoid in the156Dy doped samples followed by neutron irradiation and further chemical purification steps. The chemical behaviour of lanthanoid elements in the whole procedure was found, in separate runs, similar to that of the added156Dy within experimental errors. Simple purification steps after irradiation allow the measurement of relatively short-lived nuclides and diminish the radiation dose received during the chemical treatment. The present results for orchard leaves (NBS SRM 1571) are generally in good agreement with the previously reported data. Some new data are obtained for other biological reference materials.

Relation of contact densities with Mössbauer isomer shifts for 35.46 keV M1 transition of125Te

The internal conversion electron and Mössbauer isomer shifts associated with the 35.46 keV M1 transition of125Te were observed for different metal samples into which radioactive125I as probe atoms were introduced by means of ion-implantation. From the correlation between the Mössbauer isomer shifts and intensity ratios of O shell to NI shell conversion electrons, a relation between 5s-electron contact densityp5s(0) in a.u. and isomer shift δ in mm/s was deduced to bep5s(0)=106+30.3 δ±4.3[(δ−0.30)2+0.069]1/2, where δ was measured relative to ZnTe in mm/s. The change of the nuclear charge radius in the 35.46 keV M1 transition of125Te was found to be ΔR/R=(0.85±0.12)×10−4 (corresponding to Δ=(3.7±0.5)×10−3 fm2) when a theoretical 4s-electron contact density of 928 a.u. was used.

Estimation of the value of ΔR/R for121Sb nucleus by means of Mössbauer spectroscopy and molecular orbital calculation

The121Sb Mössbauer spectra of rapidly frozen solutions of antimony compounds were observed. The isomer shifts were compared with the electron density at the antimony nucleus calculated with the ab initio molecular orbital method. A value ΔR/R=−(11±2)×10−4 was derived for the 37.15 keV M1 transition of121Sb.

121Sb Mössbauer spectroscopic study of a series of organoantimony(III) compounds

A systematic study of organoantimony(III) compounds, SbR3, was attempted in view of the effect on Mössbauer parameters of the substituent on the aromatic ring. The Mössbauer parameters obtained in frozen organic solutions reflected the electronic effect caused by the characteristics of the substituents, electron donative or attractive, at the para position on the aromatic ring.

Determination of radon concentration in spring gases with a portable semiconductor detector

Abstract A portable integrating radon meter, alpha METER-400, was tested. The instrument detects α-rays of energy greater than 2.59 MeV. With this detector, the concentration of 222 Rn in spring gases at volcanic regions was determined. The results were compared with those observed by the liquid scintillation counting method.