Lifetime measurements of excited states in 163W

缺中子W同位素的核结构演化表明，过渡核163 W（N=89）在W同位素链中占据着一个有趣的位置。缺中子W同位素的中子费米面位于f7/2、h9/2和i13/2亚壳层轨道附近。先前的研究表明，164 W的第一个后弯是由于一对i 13/2中子的旋转排列，而在162 W中，一对h 9/2中子被发现是第一个后弯的原因。这意味着在163 W中，包含h9/2和i13/2轨道的组态应该处于相似的激发能，因此竞争形成yrast态。先前的实验已经建立了163 W中的激发态，包括建立在vi 13/2轨道上的yrast态和建立在vh 9/2和vf 7/2组态上的能带。为了测量163 W激发态的平均寿命，使用DPUNS柱塞装置与RITU充气分离器和JUROGAM II和GREAT谱仪一起进行了反冲标记的y-y符合RDDS测量。将从这些数据中提取yraast带中低能级的寿命和核变形，并在邻近同位素测量的背景下进行分析。

The evolution of nuclear structure in the neutron-deficient W isotopes has revealed that the transitional nucleus 163W (N=89) occupies an intriguing position in the chain of W isotopes. The neutron Fermi surface in the neutron-deficient W isotopes lies close to f7/2, h9/2 and i13/2 subshell orbitals. Previous studies have indicated that the first backbend in 164W is due to the rotational alignment of a pair of i13/2 neutrons, whereas in 162W a pair of h9/2 neutrons were found to be the cause of the first backbend. This implies that configurations involving h9/2 and i13/2 orbitals should be at similar excitation energies in 163W and hence compete to form the yrast states.Previous experiments have already established excited states in 163W, including yrast states built on the vi13/2 orbital and bands built on the vh9/2 and vf7/2 configurations. In order to measure the mean lifetimes of excited states in 163W, recoil-tagged y-y coincidence RDDS measurements have been performed using the DPUNS plunger device in conjunction with the RITU gas-filled separator and the JUROGAM II and GREAT spectrometers. Lifetimes and nuclear deformations of low lying states in the yrast band will be extracted from the data and analysed in the context of measurements of the neighbouring isotopes.