Isomer shifts and changes of the nuclear charge radii in99Ru and101Ru

Abstract

The recoilless nuclear gamma resonance of the 127 keV γ-rays of101Ru was observed in ruthenium metal, RuO2 and [Ru(NH3)4(HSO3)2]. By comparison of the isomer shifts observed in these materials for the 127 keV absorption line with the corresponding shifts of the 90keV γ-rays of99Ru one obtains δ〈r2〉 [127 keV]/ δ〈r2〉 [90 keV]=1.78±0.26 for the ratio of the changes of the mean square nuclear charge radii between the first excited and the ground states in these nuclei. An estimate of electron density differences based on free-ion relativistic self-consistent field calculations yields δ〈r2〉[90keV]≈+1.4·10−3 for99Ru and δ〈r2〉/〈r2〉 [127 keV]≈+2.4·10−3 for the101Ru case. These results are discussed in terms of the core excitation model.