Beta-decay energy and nuclear mass of100Nb

Radiofrequency measurements of the zero-field hyperfine intervals in low levels of¹⁶⁷Er and^161,163Dy have been made as part of a systematic study of the second half of the 4f^N6s² configuration of the neutral rare-earth atoms. Almost no precise hfs data exist for this region, and a preliminary analysis indicates systematic differences between ab initio theory and experiment.