Hyperfine structure, spin, and isotope shift measurements have been performed on ${}_{}{}^{76-98}{}_{}{}^{}\mathrm{Rb}$ and ${}_{}{}^{78,81,82,84,86,90}{}_{}{}^{}\mathrm{Rb}_{}^m{}_{}{}^{}$. The Rb nuclei have been produced either by spallation of Nb or by fission of U by a 600 MeV proton beam. They have been separated in mass before being transformed into a thermal atomic beam which interacts at a right angle with the light from a c.w. tunable dye laser. The charge radii changes deduced from the isotope shifts exhibit shell effects at $N=50\mathrm{}$ and deformations at $N=60\mathrm{}$, which are discussed.

NUCLEAR STRUCTURE ${}_{}{}^{76-98}{}_{}{}^{}\mathrm{Rb}$, ${}_{}{}^{78,81,82,84,86,90}{}_{}{}^{}\mathrm{Rb}_{}^m{}_{}{}^{}$. Measured hyperfine constants $A\left(5s{}_{}{}^2{}_{}{}^{}\mathrm{S}_{\frac{1}{2}}^{}{}_{}{}^{}\right)$, $A\left(5p{}_{}{}^2{}_{}{}^{}\mathrm{P}_{\frac{3}{2}}^{}{}_{}{}^{}\right)$, $B\left(5p{}_{}{}^2{}_{}{}^{}\mathrm{P}_{\frac{3}{2}}^{}{}_{}{}^{}\right)$; spins, isotope shifts. Deduced $\mu$, $\mathrm{Qs}$, $\delta 〈r^2〉$. High resolution laser spectroscopy on thermal atomic beams.

• Received 17 October 1980

DOI:https://doi.org/10.1103/PhysRevC.23.2720