Understanding the different rotational behaviors of ${}^{252}$No and ${}^{254}$No

Total Routhian surface calculations have been performed to investigate rapidly rotating transfermium nuclei, the heaviest nuclei accessible by detailed spectroscopy experiments. The observed fast alignment in ${}^{252}$No and slow alignment in ${}^{254}$No are well reproduced by the calculations incorporating high-order deformations. The different rotational behaviors of ${}^{252}$No and ${}^{254}$No can be understood for the first time in terms of ${\beta }_6$ deformation that decreases the energies of the $\nu j_{15/2}$ intruder orbitals below the $N=152$ gap. Our investigations reveal the importance of high-order deformation in describing not only the multiquasiparticle states but also the rotational spectra, both providing probes of the single-particle structure concerning the expected doubly magic superheavy nuclei.

Figure 1

Experimental kinematic (a) and dynamic (b) moments of inertia for ${}^{252,254}$No. Data are taken from Refs. [13, 14] for ${}^{252}$No and ${}^{254}$No, respectively.

Figure 2

Calculated kinematic moments of inertia for Fm, No, and Rf isotopes, compared with available experimental data [4, 5, 6, 10, 11, 12, 13, 14]. Calculations with and without high-order deformations ${\beta }_{6,8}$ are represented by open circles (red) and open triangles (blue), respectively. Filled squares (black) indicate experimental data.

Figure 3

Proton (a) and neutron (b) components of the calculated kinematic moments of inertia for ${}^{252,254}$No.

Figure 4

Calculated ${\beta }_2$ (a), ${\beta }_4$ (b), ${\beta }_6$ (c), and ${\beta }_8$ (d) deformations vs rotational frequency for ${}^{252,254}$No.