Muonic x-ray spectra have been measured for ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ and ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$. From the data we have determined model-independent charge radii and isomer shifts of certain excited nuclear states and have inferred spectroscopic quadrupole moments of excited states for both isotopes. The quadrupole moment of the lowest $\frac{5}{2^{-}}$ state in ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ is found to be positive, in agreement with previous muonic-atom data but in disagreement with a recent Mössbauer study. $B\left(E2\mathrm{}\right)\mathrm{}$ values of low-lying excited states have been determined for ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$. An $E1\mathrm{}$ muonic-nuclear resonance has been discovered in ${}_{}{}^{200}{}_{}{}^{}\mathrm{Hg}$.

NUCLEAR STRUCTURE ${}_{}{}^{199,200}{}_{}{}^{}\mathrm{Hg}$; measured muonic x-ray spectra; deduced monopole and quadrupole charge parameters, isomer shifts.

• Received 30 August 1982

DOI:https://doi.org/10.1103/PhysRevC.27.816