Measurement of the Σ−→ne −¯v and Σ−→ nμ−¯v rates

The recoilless nuclear resonance absorption of the 90 keVγ-rays of⁹⁹Ru was observed in a variety of chemical compounds of ruthenium in the oxidation states +2 through +8 at 4.2 ° K. For most of the compounds isomer shifts increasing monotonically with the oxidation state of ruthenium were found. This behaviour, which may essentially be attributed to the decreasing number of 4d electrons, and the few exceptions from it are discussed qualitatively on the basis of the molecular orbital theory.