Charge Radii of Argon Isotopes in the f7/2 Shell and Radii Systematics in the Ca-Region

Changes in mean square (ms) nuclear charge radii of Ar isotopes across the 1f7/2 shell are studied by fast-beam collinear laser spectroscopy using an ultra-sensitive detection method based on optical pumping and state-selective collisional ionization. The new data set on Ar, in combination with the known charge radii of K, Ca and Ti in the n1f7/2 shell, offers an opportunity to obtain a more complete overview of nuclear radii trends around the proton shell closure Z =2 0 and between the neutron shell closures N =2 0 andN = 28.