Isotope Shift of Eleven Cesium Isotopes Determined by Atomic-Beam Laser Spectroscopy

Isotopes of ${}_{}{}^{123-137}{}_{}{}^{}\mathrm{Cs}$ produced by spallation of lanthanum and separated in mass by the ISOLDE on-line facility have been transformed into an atomic beam which is illuminated with a tunable cw dye laser. From the sensitive detection of the optical resonance lines at 459 nm, the hyperfine structure of ${}_{}{}^{123-132}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{137}{}_{}{}^{}\mathrm{Cs}$, and ${}_{}{}^{130m}{}_{}{}^{}\mathrm{Cs}$ has been determined. The interpretation of isotope shifts, in terms of variation of charge radii, is discussed.