| Source: |
Andreyev, A N, Barzakh, A, Seliverstov, M D, Yue, Z, Liu, M, Yuan, C, Algora, A, Andel, B, Antalic, S, Al Monthery, M, Atanasov, D, Benito, J, Benzoni, G, Berry, T, Bissell, M L, Blaum, K, Borge, M J G, Chrysalidis, K, Clisu, C, Cocolios, T E, Costache, C, Cubiss, J G, Day Goodacre, T, Farooq-Smith, G J, Fedorov, D V, Fedosseev, V N, Fraile, L M, Fynbo, H O U, Gadelshin, V, Gaffney, L P, Ruiz, R F G, Granados, C, Greenlees, P T, Harding, R D, Harkness-Brennan, L J, Heinke, R, Herlert, A, Huyse, M, Illana, A, .... |
| Description: |
The nuclear properties of bismuth isotopes (Z=83), with just one valence proton above the closed spherical shell at Z=82, are expected to be governed by a single unpaired proton. However, already in semimagic 209 Bi (Z=83, N=126), the magnetic moment ( μ ) strongly deviates from the single-particle Schmidt value. A near linear decrease in μ with the increase of N after the N=126 magic number was observed up to N=130. In order to test whether this trend is kept at N > 130 and to reveal the underlying mechanisms, an investigation of 215,217 Bi (N=132,134) has been undertaken. The magnetic dipole and electric quadrupole moments of the I π =9/2 − nuclear ground states in these isotopes have been measured for the first time using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). It has been shown that the linearly decreasing trend of μ ( 209,211,213 Bi g ) is broken in 215,217 Bi with a nearly constant value of μ observed. Experimental data have been compared to calculations in the framework of the configuration-interaction shell model with the monopole-based universal V MU +LS interaction. The peculiarities in the behavior of μ (Bi, 9/2 − ) with increasing neutron number are explained as being due to the shell evolution, change of the neutron orbitals occupancies and strong configuration mixing beyond N=130. Also, the difference in the μ trends for bismuth (Z=83) and astatine (Z=85) isotopes with N > 126 are reproduced by the shell-model calculations. It is shown that monopole interaction plays noticeable role in the description of the peculiarities of the μ behaviour. Additionally, the extension of the application of the V MU interaction to the μ isotopic trends for heavy nuclei is important for further study of the capabilities of this promising version of the shell-model calculations. |