We report on the measurement of optical isotope shifts for 38,39,42,44,46-51K relative to 47K from which changes in the nuclear mean square charge radii across the N=28 shell closure are deduced. The investigation was carried out by bunched-beam collinear laser spectroscopy at the CERN-ISOLDE radioactive ion-beam facility. Mean square charge radii are now known from 37K to 51K, covering all νf7/2-shell as well as all νp3/2-shell nuclei. These measurements, in conjunction with those of Ca, Cr, Mn and Fe, provide a first insight into the Z dependence of the evolution of nuclear size above the shell closure at N=28.
@article{arxiv.1310.5171,
title = {Nuclear charge radii of potassium isotopes beyond N=28},
author = {K. Kreim and M. L. Bissell and J. Papuga and K. Blaum and M. De Rydt and R. F. Garcia Ruiz and S. Goriely and H. Heylen and M. Kowalska and R. Neugart and G. Neyens and W. Nörtershäuser and M. M. Rajabali and R. Sánchez Alarcón and H. H. Stroke and D. T. Yordanov},
journal= {arXiv preprint arXiv:1310.5171},
year = {2015}
}