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Description
The low-energy multipole spectrum in isotopes $^{250-260}No$ is investigated in the framework of fully self-consistent Quasiparticle-Random-Phase-Approximation (QRPA) method [1, 2] with Skyrme forces. The main attention is paid to nuclei $^{250,252,254}No$, where we have most of the experimental spectroscopic information [3, 4]. In general, a good agreement with the experimental data is obtained. It is shown that, in the chain $^{250−260}No$, features of $^{252}No$ and $^{254}No$ exhibit essential irregularities caused by a shell gap in the neutron single-particle spectra and corresponding break of the neutron pairing. The low-energy pairing-vibrational $K^π = 0^+$ state is predicted in $^{254}No$. In addition to low-energy one-phonon collective states (lm=20,22,30,31,32,43) and K-isomers ($K^π = 2^-,8^-,3^+$) will be shown [5].
Isotopes of No are attracting attention, as there are new experimental data on M1 excitation for $^{254}No$ [6]. The main attention is paid to orbital and spin M1 excitations. Lowest $K^π =1^+$ states in $^{254}No$ have a spin-scissor character and seen as collective excitation of orbital mode. In particular, the interference of spin and orbital degrees of freedom is investigated.
[1] P.-G. Reinhard, B. Schuetrumpf, and J. A. Maruhn, Comp. Phys. Commun. 258, 107603 (2021).
[2]A. Repko, J. Kvasil, V.O. Nesterenko and P.-G. Reinhard, arXiv:1510.01248[nucl-th].
[3] R.-D. Herzberg and P.T. Greenlees, Prog. Part. Nucl. Phys. 61, 674 (2008).
[4] R.-D. Herzberg, arXiv:2309.10468[nucl-ex].
[5] V. O. Nesterenko, M.A. Mardyban, R.V. Jolos, P.-G. Reinhard, A. Repko, A. A. Dzhioev, Phys. Rev. C. (submitted May, 2025).
[6] F.L. Bello Garrote et all, Phys. Lett. B834, 137479 (2022).
