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Modern techniques of laser spectroscopy enable measurements of optical isotope shifts and hyperfine structures to be extended across long chains of isotopes reaching far from the region of stability. While the hyperfine structure yields precise information on the spin and electromagnetic moments of the nucleus, the isotope shifts are sensitive to small differential changes in size and shape of the nuclear charge distribution. The experimental situation is reviewed, with an emphasis on the techniques used for rare and radioactive species. The status of the experimental data is summarized. Modified King plots are used to make a detailed inspection of the apparent similarities seen between neighbouring chains in different regions of the nuclear chart.

The first on-line laser spectroscopy of cooled fission fragments is reported. The r ions, produced in uranium fission, were extracted and separated using an ion guide isotope separator. The ions were cooled and bunched for collinear laser spectroscopy by a gas-filled linear Paul trap. New results for nuclear mean-square charge radii, dipole, and quadrupole moments are reported across the N=60 shape change. The mean-square charge radii are found to be almost identical to those of the Sr isotones and previously offered modeling of the radial changes is critically reviewed.

A new method has been developed for increasing the sensitivity of collinear laser spectroscopy. The method utilizes an ion-trapping technique in which a continuous low-energy ion beam is cooled and accumulated in a linear Paul trap and subsequently released as a short (10-20 micros) bunch. In collinear laser measurements the signal-to-noise ratio has been improved by a factor of 2 x 10(4), allowing spectroscopic measurements to be made with ion-beam fluxes of approximately 50 ions s(-1). The bunching method has been demonstrated in an on-line isotope shift and hyperfine structure measurement on radioactive (175)Hf.

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