The isotope shift of an optical transition $(\lambda =534.93\mathrm{}\hspace{0.5em}\mathrm{nm})$ in ${\mathrm{Ce}}^{+}$ for radioactive ${}^{144}\mathrm{Ce}$ has been measured by collinear laser-ion-beam spectroscopy as well as those of stable isotopes. The change in mean-square nuclear charge radius determined from the isotope shift is $\delta 〈r^2{〉}^{142,144}=0.232\mathrm{}\left(20\right)\mathrm{}\hspace{0.5em}{\mathrm{fm}}^2,$ and compared with the values from the reduced $E2\mathrm{}$ transition probability and the theoretical predictions.

• Received 5 October 1998

DOI:https://doi.org/10.1103/PhysRevC.59.1794