Abstract
The nucleus 177 Lu is characteristic by an unusually high value of the thermal-neutron capturing state spin, J = 13/2, and by distinct low-energy rotational bands built on the 7/2 + ground state and the 9/2 − level at 150 keV. The γ cascades connecting the capturing state with the members of these bands carry unique infor- mation about the role of identical M1 scissors-mode resonances, built according to Brink hypothesis assumingly on each energy level, even in conditions of fast nuclear rotation. With this motivation we measured a set of spec- tra of two-step γ cascades following the thermal neutron capture in 176 Lu. The measurement was performed at neutron beam of the LWR-15 Reactor in ˇ Reu. From the analysis of these spectra the common parameters of the scissors resonances were deduced. The obtained results are discussed.
Highlights
Photon strength functions (PSF) are essential quantities for the statistical description of γ decay of highly-excited nuclear levels
In our simplified interpretation the SM, expressed as a broad bump in the mid of two-step cascades (TSCs) spectra, is responsible for a significant or even dominating part of the total strength of the TSC spectra. We found that this bump cannot be attributed to any additional resonance-like component of the E1 or E2 photon strength
A strong role of SM in the cascade γ decay of neutron capturing state of 177Lu is beyond any doubt
Summary
Photon strength functions (PSF) are essential quantities for the statistical description of γ decay of highly-excited nuclear levels. The method of two-step cascades (TSCs) proved to be a powerful tool for studying PSFs. Here we report the results on PSFs obtained from analysis of spectra of TSCs following the thermal neutron capture in 176Lu. The spin and parity Jπ = 13/2− of the neutron capturing state enabled us to investigate the SM coupled to excited levels with high spin in strongly deformed nucleus 177Lu. 2 Experiment and data analysis
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