Microscopic study of the low-energy enhancement in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> -decay strength of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mi m
We address the microscopic origin of the low-energy enhancement (LEE) in \(^{50}\)V with large-scale shell-model calculations to obtain $E1$ and $M1$ transitions within the same theoretical framework. The valence space spans the three major shells $sd$, $pf$ and $sdg$ and is treated with the SDPFSDG-MU interaction using the KSHELL code. With a \(1 \hbar ω\) truncation, 3600 energy eigenstates and a basis of $7.02\times10^{6}$ positive and $5.94\times10^{8}$ negative parity states, the calculations yield nearly two million individual dipole transitions. The fourteen lowest experimental levels are reproduced within $0.30$~MeV, the calculated total level density excellently reproduces Oslo-method data up to $E \approx 7.5$~MeV, and the calculated dipole gamma strength function follows the experimental shape -- including the LEE -- for the full gamma-energy range covered by the Oslo experiment. The LEE is shown to be entirely magnetic dipole in origin. Both spin and orbital parts of the \(\hat{M}1\) operator are required to reproduce the LEE, with constructive interference between the spin and orbital parts giving an extra enhancement to the LEE. Reduced one-body transition densities identify $0f_{7/2} \rightarrow 0f_{7/2}$ proton transitions as the principal driver of the LEE.
Authors
- Y. Utsuno (ORCID: https://orcid.org/0000-0001-5404-7320)
- Anonymous
- N. Shimizu
- A. C. Larsen
Institutions
- Japan Atomic Energy Agency (JP)
- University of Tsukuba (JP)
- University of Oslo (NO)
- The University of Tokyo (JP)
Publication Details
- Journal
- Physical review. C
- Published
- 2026-01-26
- DOI
- https://doi.org/10.1103/csx6-6g5k
- Primary Topic
- Nuclear physics research studies
- Type
- article
- Field-Weighted Citation Impact
- 0.00