High-K multi-particle bands and pairing reduction in ²⁵⁴No *

Abstract

The multi-particle states and rotational properties of two-particle bands in 254 No are investigated by the cranked shell model (CSM) with pairing correlations treated by a particle-number conserving (PNC) method. For the first time, the rotational bands on top of two-particle K π = 3 + , 8 − and 10 + states and the pairing reduction are studied theoretically in 254 No. The experimental excitation energies and moments of inertia for the multi-particle state are reproduced well by the calculation. Better agreement with the data are achieved by including the high-order deformation ε6 which leads to enlarged Z = 100 and N = 152 deformed shell gaps. The rise of the J (1) in these two-particle bands compared with the ground-state band is attributed to the pairing reduction due to the Pauli blocking effects.

Decay studies of new isomeric states in No255

“…We attribute the dominant peaks with energies 8088 ± 10 keV and 7429 ± 10 keV to α decays of 254 No and 250 Fm, respectively. In addition, a few hundreds of 252 No nuclei were produced by the reaction of 48 Ca with 206 Pb impurities in the target material (Fig. 1).…”

“…Two experiments using the same projectile-target combination were performed at GSI in Darmstadt, Germany. The first experiment aimed at the investigation of 255 No α decay (Exp1) used a kinetic energy of E lab = 213.6 MeV for 48 Ca projectiles. The second experiment (Exp2) was focused on a detailed study of isomeric states in 254 No using a higher projectile energy (E lab = 218.4 MeV).…”

“…In both experiments, the 48 Ca beam was delivered by the ECR ion source followed by the UNILAC accelerator. The isotopically enriched target material 208 PbS with a thickness of 450 μg/cm 2 was evaporated on a 40 μg/cm 2 carbon layer facing the beam.…”

“…The 3-qp configuration with the lowest excitation energy and K = 19/2, K = 21/2, or K = 23/2, which consists of a proton pair andν 11/2 − [725], is 1/2 − [521] ⊗ 9/2 + [624] ⊗ 11/2 − [725](see Fig.7and TableIX). However, as calculations of 2-qp states excitation energies can differ significantly (see, e.g., Refs [48][49][50]…”

The alternating-parity bands of \element{236,238}{U} and \element{238,240}{Pu} in a particle-number conserving method based on cranked shell model

“…The particle number is conserved and the Pauli blocking effect is treated spontaneously. The PNC-CSM method has previously been applied successfully to describe the intrinsic reflection-symmetric system from the light nuclear mass region around A = 40 [41] to the very heavy region around A = 250 [42][43][44][45].…”