Rotational properties of the odd-Z transfermium nucleus 255Lr by a particle-number-conserving method in the cranked shell model

Experimentally observed ground state band based on the 1/2^?521] Nilsson state and the first exited band based on the 7/2^?514] Nilsson state of the odd-Z nucleus ²⁵⁵Lr are studied by the cranked shell model (CSM) with the paring correlations treated by the particle-number-conserving (PNC) method. This is the first time the detailed theoretical investigations are performed on these rotational bands. Both experimental kinematic and dynamic moments of inertia (J⁽¹⁾ and J⁽²⁾) versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia J⁽¹⁾ with the experimental ones extracted from different spin assignments, the spin 17/2^? → 13/2^? is assigned to the lowest-lying 196.6(5) keV transition of the 1/2^?521] band, and 15/2^? → 11/2^? to the 189(1) keV transition of the 7/2^?514] band, respectively. The proton N = 7 major shell is included in the calculations. The intruder of the high-j low-Ω 1j_15/2 (1/2^?770]) orbital at the high spin leads to band-crossings at ?ω ≈ 0.20 (?ω ≈ 0.25) MeV for the 7/2^?514] α = ?1/2 (α = +1/2) band, and at ?ω ≈ 0.175 MeV for the 1/2^?521] α = ?1/2 band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.