Influence of theN=50shell closure on mean square charge radii of strontium

Abstract

Isotope shifts of the stable strontium isotopes Sr, Sr, Sr, and ' Sr and the radioactive isotopes Sr and Sr have been measured using laser spectroscopy on collimated atomic beams. The changes in mean square charge radii extracted from the isotope shifts show a pronounced shell effect at the closed neutron shell 1V =50. The experimental data are compared with the predictions of the droplet model and Hartree-Fock plus BCS calculations. The analysis suggests that the changes in mean square charge radii are due to a change in size, a change in the predominantly dynamic deformation, and a change in the diffuseness of the nuclear charge distribution.

Charge radii and moments of strontium nuclei by laser spectroscopy

“…4a and b. In view of the calibration problem it is not surprising that our results differ somewhat from others as, e.g., [13].…”

“…The rotational model of permanently deformed nuclei, though often used as convenient parametrization, is not justified for the results found for A > 80. The experimental results of 6 (r 2) for 89'9~ beyond the closed neutron shell at N= 50 are well reproduced by microscopic calculations [13]. A remarkable feature of the ms radius variation is an odd-even staggering superimposed on the deformation effects.…”

“…The first pioneering optical investigation of radioactive 9~ was by K. Heilig [12] who used a hollow cathode discharge lamp with samples of 1 gg Sr. Radioactive 89Sr to-gether with 9~ was studied by F. Buchinger et al [13] using laser spectroscopic techniques. The isotope shift of unstable 828r was measured by A.G. Martin et al [14].…”

Laser-spectroscopy measurements of 72–96Kr spins, moments and charge radii

“…Here, the radii increase steadily from the spherically shaped 86 Kr through the transitional region to the strongly deformed nuclei around N = 40. The very sharp kink at N = 50 and the increase of the radii with decreasing neutron number for N < 50 is a general feature also observed for the isotones in rubidium 6, 7] and strontium 10,45]. Although the droplet model calculations in this region are based on directly measured B(E2) values, they fail to reproduce the described trends except for the strongly deformed isotopes around N = 40.…”

Charge and mass radii of the tin isotopes

“…Also, LS coupling closed shells where both members of the spin-orbit doublet are completely full or empty, make no contribution to (2.9). On the other hand, 4SCa [7], 8SSr [28] and lZgSn do show significant EMSO effects. In 2~ the opposite sign of/~v, /i, leads to a cancellation between proton and neutron contributions, but 2~…”