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This paper is devoted to the analysis of the general trends in the nucleon number dependence of the experimental root-mean-square (rms) charge radii. It is based on the data obtained by different methods of combined treatment of (i) radii changes determined from optical and—to a lesser extent—Kαx-ray isotope shifts, and (ii) absolute radii measured from muonic and electronic scattering experiments. These methods have recently been developed and now updated including experimental data up to the beginning of 2008. Thus, new sets of rms nuclear radii have been obtained covering 865 isotopes for 76 elements from 1H to 96Cm. New information on the isotopic and isotonic behaviour of the nuclear charge radius is obtained with a high accuracy compared to that of the directly measured radii values for the same element. Of special interest is that concerning the light elements and the appearance of non-traditional magic neutron and proton numbers, as N = 6, 14 and Z = 14; the double-magic properties of 96Zr are discussed in more detail. A quantitative criterion is introduced, which points to the peculiarities in the radii trend and offers an opportunity to investigate it more closely. The results provide important information which may serve as a guide to incorporate essential new features into the theoretical approaches.

Abstract. Collinear laser spectroscopy experiments with the Sc + transition 3d4s 3 D 2 → 3d4p 3 F 3 at λ = 363.1 nm were performed on the 42−46 Sc isotopic chain using an ion guide isotope separator with a cooler-buncher. Nuclear magnetic dipole and electric quadrupole moments as well as isotope shifts were determined from the hyperfine structure for five ground states and two isomers. Extensive multi-configurational Dirac-Fock calculations were performed in order to evaluate the specific mass-shift, M SMS , and field-shift, F , parameters which allowed evaluation of the charge radii trend of the Sc isotopic sequence. The charge radii obtained show systematics more like the Ti radii, which increase towards the neutron shell closure N = 20, than the symmetric parabolic curve for Ca. The changes in mean square charge radii of the isomeric states relative to the ground states for 44 Sc and 45 Sc were also extracted. The charge radii difference between the ground and isomeric states of 45 Sc is in agreement with the deformation effect estimated from the B(E2) measurements but is smaller than the deformation extracted from the spectroscopic quadrupole moments.

Optical isotope shifts of the unstable 44,45Ti isotopes, as well as those of stable 46−50Ti, have been investigated by collinear laser spectroscopy on fast ion beams using an ion guide isotope separator with a cooler-buncher. Changes in mean square charge radii across the neutron 1f7/2 shell are deduced. The evolution of the even-N Ti nuclear radii shows a generally increasing tendency with decreasing neutron number. This behaviour is significantly different to that of the neighbouring Ca isotopes which exhibit a symmetric parabolic behaviour across the shell. The trend of the Ti nuclear radii is consistent with the predictions of the relativistic mean-field theory. The charge radius of 44Ti is also compared to predictions of a 40Ca + α cluster model.

Atomic beam laser spectroscopy was used to measure the isotope shifts (IS) and hyperfine structures of all stable titanium isotopes in eight Ti I spectral lines. Six of the lines investigated cover all allowed transitions between the lower 3d24s2 a 3P and the upper 3d34p y 3Do terms; two of them are between the 3d24s2 a 3P1,2 and 3d24s4p z 3P2o levels. J-dependences of the IS in the a 3P and y 3Do terms were established. The contributions of the field and mass shifts to the J-dependence were separated using model-independent data on muonic atom IS and electronic scattering experiments. Evidence for mass shift domination of the J-dependence was provided.