Nd+ isotope shift measurements in a cryogenically cooled neutral plasma

Abstract

We report measurements of the isotope shifts of two transitions (4f 4 6s → [25044.7] • 7/2 and 4f 4 6s → [25138.6] • 7/2 ) in neodymium ions (Nd + ) with hundredfold improved accuracy, using laser spectroscopy of a cryogenically-cooled neutral plasma. The isotope shifts were measured across a set of five spin-zero isotopes that spans a nuclear shape transition. We discuss the prospects for further improvements to the accuracy of Nd + isotope shifts using optical clock transitions, which could enable higher precision tests of King plot linearity for new physics searches.