Precision measurements have been made of the muonic x-ray spectra of the transitional nuclei ${}_{}{}^{186,188,190,192}{}_{}{}^{}\mathrm{Os}$. Equivalent Barrett radii and isotope shifts have been determined, as have isomer shifts of the first excited $2^{+}$ states. These results are compared with other experiments and with theoretical calculations. The systematics of isotope shifts in the deformed nuclei are also discussed. Generalized $E2$ moments of the charge distribution have been extracted in a nearly model-independent way and conventional electromagnetic moments have been deduced by assuming a specific transition charge density model. The latter are in good agreement with recent calculations of both the interacting boson approximation and the boson expansion theory. However, a serious discrepancy in the values of the quadrupole moments determined from the muonic and Coulomb excitation experiments is apparent. The model dependence of the muonic results (including the effect of a triaxial model charge distribution) is explored as a possible cause of the discrepancy; however, no effect large enough to explain the discrepancy is found. Furthermore, no feature of the muonic spectra was found which could be used to distinguish between a triaxial and an axially symmetric charge distribution.

NUCLEAR STRUCTURE ${}_{}{}^{186,188,190,192}{}_{}{}^{}\mathrm{Os}$; measured muonic x-ray spectra; deduced monopole and quadrupole charge parameters, isotope and isomer shifts.

• Received 24 February 1981

DOI:https://doi.org/10.1103/PhysRevC.24.1667