Magnetic Dipole Moment of the Doubly-Closed-Shell Plus One Proton Nucleus Sc49

The nucleus Sc49, having a single f_7/2 proton outside doubly magic Ca48 (Z=20, N=28), is one of the very few isotopes which makes possible testing of the fundamental theory of nuclear magnetism. The magnetic moment has been measured by online β NMR of nuclei oriented at milli-Kelvin temperatures to be (+)5.616(25)μ_N. The result is discussed in terms of a detailed theory of the structure of the magnetic moment operator, showing excellent agreement with calculated departure from the f_7/2 Schmidt limit extreme single-particle value. The measurement completes the sequence of moments of Sc isotopes with even numbers of f_7/2 neutrons: the first such isotopic chain between two major shells for which a full set of moment measurements exists. The result further completes the isotonic sequence of ground-state moments of nuclei with an odd number of f_7/2 protons coupled to a closed subshell of f_7/2 neutrons. Comparison with a recent shell-model calculation of the latter sequence is made.