Nuclear moments and charge radii of argon isotopes between the neutron-shell closures N=20 and N=28
Blaum, K Geithner, W Lassen, J Lievens, Peter Marinova, K Neugart, R # ×
Elsevier science bv
Nuclear physics a vol:799 pages:30-45
We report the measurement of optical isotope shifts for Ar40-44 relative to Ar-38 from which changes in the mean square nuclear charge radii across the 1 f(7/2) neutron shell are deduced. In addition, the hyperfine structure of Ar-41 and Ar-43 yields the spins, magnetic dipole and electric quadrupole moments, in particular the spin I = 5/2 for Ar-43. The investigations were carried out by fast-beam collinear laser spectroscopy using highly sensitive detection based on optical pumping and state-selective collisional ionization. Mean square charge radii are now known from Ar-32 to Ar-46, covering sd-shell as well as f(7/2)-shell nuclei. They are discussed in the framework of spherical SGII Skyrme-type Hartree-Fock calculations, semi-empirically corrected for quadrupole core polarization. The Zamick-Talmi formula excellently describes the charge radii across the f(7/2) neutron shell, as it does for the neighbouring elements. The new data on Ar, in addition to those on K, Ca and Ti, provide an extended overview of nuclear radii trends around Z = 20 and between N = 20 and N = 28. Characteristic features are discussed, the most striking being the absence of any isotopic shell effect in the radii at N = 20. (c) 2007 Elsevier B.V. All rights reserved.