The β-decays of neutron-rich carbon,nitrogen and fluorine isotopes have been sys-tematically studied using the OXBASH shell Model.In the psd,spsd and spsdpf model space,we use the W BP interaction to calculate the half-lives and neutron emission probabilities of neutron-rich carbon and nitrogen isotopes,respectively.With the USD (W) and CW interactions,we calculate the half-lives and neutron emission probabilities of neutron-rich fluorine isotope in the sd model space,respectively.The calculated half-lives and neutron emission probabilities repro-duce recent experimental data very well.It seems to show that the particles of the neutron-rich carbon and nitrogen isotopes are mainly excited in the spsd space.The β-decay of 21N to the neutron bound states in 21O is mostly the first forbidden transition which makes the neutron emission probability increase.The theoretical calculation of β-decay of 25F to 25Ne with CW interaction shows that CW interaction is better than USD interaction.
Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam experiments, and the main results including energy resolution, peak-to-total ratios, the variation of the hit pattern distribution in different crystals of one Clover detector with the energy of γ ray, and absolute full energy peak detection effciency curve, were presented.
High-spin states in 157yb have been populated in the 144Sm(16O, 3n)157yb fusion-evaporation reaction at a beam energy of 85 MeV, and two rotational bands have been established for the first time. Within the framework of the triaxial particle-rotor model, the energy spectra and single-particle configurations of 157yb are investigated. The calculated energy spectra agree well with the experimental data. The newly observed vf7/2 band, and the previously known vi13/2 band in 157yb, are also discussed by means of Total-Routhian-Surface methods. The structural characters observed in 157Yb provide evidence for the shape coexistence of three distinct shapes: prolate, triaxial and oblate. At higher spins, both the vf7/2 band and the vi13/2 band in 157yb undergo a shape evolution with sizable alignments occurring.
High-spin states of 156Yb have been studied via the 144Sm(16O,4n)156Yb fusion-evaporation reaction at beam energy 102 MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. The characteristics of the negative-parity sequence above the 25-state may related to the excitation from the nucleon in the Z =64, N =82 core. The E-GOS curve for the positiveparity yrast sequence in 156Yb indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. The Cranked Woods-Saxon-Strutinsky calculations by means of Total-Routhian-Surface (TRS) methods has been made to understand this structure change.
