Charge radii and nuclear moments of neutron-deficient potassium isotopes*

The monotonic change of charge radii of K isotopes across $N$ = 20 suggests a reduction of the shell gap. A systematic study of the charge radii and ground state magnetic and quadrupole moments of neutron-deficient $^{35-37}$K isotopes is underway at the BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL/MSU to investigate the anomalous trend in charge radii. The K isotopes were produced by fragmentation of a $^{40}$Ca beam, thermalized in a linear gas cell, extracted at an energy of 30 keV, and transported to BECOLA. The K ion beam was cooled and bunched, and neutralized in a Na vapor cell. Laser-induced fluorescence was detected as a function of the Doppler-tuned laser frequency and time relative to the release of the beam bunch. The beta-NMR technique was used to determine ground-state nuclear moments, where hyperfine splittings are too small to resolve using collinear laser spectroscopy.