H. B. Sun

Evolution of the X(5) critical-point symmetry in rotating \mathrm{\mathbf {^{176}Os}}

Lifetimes of excited states above 10+ in the yrast band in 176Os have been measured using the Doppler shift attenuation method, via the fusion evaporation reaction . Lifetimes of states over 12+ were measured for the first time. The deduced transitional quadruple moments (Qt), together with the previous data using a recoil distance method, are compared with theoretical calculations based on the X(5) model and the interaction boson model. For the states below spin 10+, the data of previous work support an X(5)-like structure, but for the states above 10+, the value of Qt remains almost constant, being the characteristic of a symmetric rotor. The present result suggests that the shape of the nucleus 176Os changes from X(5) critical-point symmetry to an axially deformed rotor with increasing spin.

Radii of the bound states in 16 N from the asymptotic normalization coefficients

The asymptotic normalization coefficients (ANCs) of the virtual decay 16N → 15N + n are extracted from the 15N(7Li, 6Li)16N reaction populating the ground and first three excited states in 16N. The root-mean-square (rms) radii of the valence neutron in these four low-lying 16N states are then derived by using the ANCs. The probabilities of the valence neutron staying out of the core potentials are found to be 31% ± 8%, 58% ± 12%, 32% ± 8%, and 60% ± 12%. The present results support the conclusion that a one-neutron halo may be formed in the 16N first and third excited states, while the ground and second excited states do not have a one-neutron halo structure. However, the core excitation effect has a strong influence on the one-neutron halo structure of the ground and first excited states in 16N.