Charge Radii of Neutron Deficient 52;53Fe Produced by Projectile Fragmentation

Bunched-beam collinear laser spectroscopy is performed on neutron deficient Fe-52,Fe-53 prepared through in-flight separation followed by a gas stopping. This novel scheme is a major step to reach nuclides far from the stability line in laser spectroscopy. Differential mean-square charge radiI delta < r(2)> of Fe-52,Fe-53 are determined relative to stable Fe-56 as delta < r(2)>(56,52) = -0.034(13) fm(2) and delta < r(2)>(56,53) = -0.218(13) fm(2), respectively, from the isotope shift of atomic hyperfine structures. The multiconfiguration Dirac-Fock method is used to calculate atomic factors to deduce delta < r(2)>. The values of delta < r(2)> exhibit a minimum at the N = 28 neutron shell closure. The nuclear density functional theory with Fayans and Skyrme energy density functionals is used to interpret the data. The trend of delta < r(2)> along the Fe isotopic chain results from an interplay between single-particle shell structure, pairing, and polarization effects and provides important data for understanding the intricate trend in the delta < r(2)> of closed-shell Ca isotopes.