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Oslo method and neutron-capture $\gamma$ decay experimenents on heavy deformed nuclei systematically show a resonance-like structure around 2 - 3 MeV in the gamma strength function (GSF) interpreted as the scissors mode in the quasicontinuum. Its $M1$ character has been demonstrated by polarization experiments [1] and its strength may be connected to the low-energy enhancement phenomeon in Oslo-type experiments [2]. One of the longstanding questions is whether the integrated strength differs from the systematics derived from g.s. excitation experiments [3]. A recent compilation shows that experimental results scatter from approximate agreement to about four times the g.s. strength [4].
We have reanalyzed data from a recent Oslo experiment on $^{150}$Nd [5] aiming at a systematic fit of the GSF similar to Ref. [6] to constrain the background from the low-energy tail of the GDR. In the studied excitation energy range of about 4.5 - 7.5 MeV results are independent of initial or final energy consistent with the generalized Brink-Axel hypothesis. However, the absolute strength is 5.9(2) $\mu_N^2$, i.e. about twice the g.s. strength. Possible interpetations in the framework of an angular momentum-projected shell model [7] are discussed.
[1] F. Bello Garrote et al., Phys.Lett. B 834, 137479 (2022)
[2] R. Schwengner et al., Phys. Rev. Lett. 118, 092502 (2017)
[3] K. Heyde et al. Rev. Mod. Phys. 82, 2365 (2010)
[4] F. Pogliano et al., Phys. Rev. C 107, 034605 (2023)
[5] M. Guttormsen et al., Phys. Rev. C 106, 034314 (2022)
[6] M. Markova et al., Phys. Rev. C 109, 054311 (2024)
[7] F.-Q. Chen et al., Phys. Rev. Lett. 134, 082502 (2025)