Spectroscopy of ${}^{50}$Sc and ab initio calculations of $B(M3)$ strengths

Abstract

The GRIFFIN spectrometer at TRIUMF-ISAC has been used to study excited states and transitions in ${}^{50}$Sc following the $\beta$-decay of ${}^{50}$Ca. Branching ratios were determined from the measured $\gamma$-ray intensities, and angular correlations of $\gamma$ rays have been used to firmly assign the spins of excited states. The presence of an isomeric state that decays by an $M3$ transition with a $B(M3)$ strength of 13.6(7)\,W.u. has been confirmed. We compare with the first {\it ab initio} calculations of $B(M3$) strengths in light and medium-mass nuclei from the valence-space in-medium similarity renormalization group approach, using consistently derived effective Hamiltonians and $M3$ operator. The experimental data are well reproduced for isoscalar $M3$ transitions when using bare $g$-factors, but the strength of isovector $M3$ transitions are found to be underestimated by an order of magnitude.

References in corpus (12)

• Chiral effective field theory and nuclear forces
• Improved nuclear matter calculations from chiral low-momentum interactions
• Accurate nuclear radii and binding energies from a chiral interaction
• Similarity Renormalization Group for Nucleon-Nucleon Interactions
• A nucleus-dependent valence-space approach to nuclear structure
• Local chiral effective field theory interactions and quantum Monte Carlo applications
• A new effective interaction for $0\hslash \omega$ shell model calculations in the sdpf valence space
• Importance Truncation for Large-Scale Configuration Interaction Approaches
• In-Medium Similarity Renormalization Group for Open-Shell Nuclei
• Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths
• The GRIFFIN Data Acquisition System
• Half-lives of neutron-rich ${}^{128-130}$Cd

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• Testing ab initio nuclear structure in neutron-rich nuclei: lifetime measurements of second 2+ states in 16C and 20O