Systematic investigation of the collective structure of neutron-rich even-even nuclei with 50 < Z < 82 via recoil-distance Doppler shift lifetime measurements of excited nuclear states using the two neutron transfer reaction.

我们计划在核图的50 < Z < 82区域进行双中子转移反应，以研究不同的核结构现象。感兴趣的原子核是152、156Sm、160、162 gd、178Yb、182Hf、188W、194Os和200Pt，它们将在18O束流的双中子转移反应中填充。光束由科隆10 MV串联加速器提供，光束能量在相应反应的库仑势垒附近。科隆柱塞光谱仪配备了25个高纯锗（HPGe）探测器和8个LaBr（Ce）探测器，将用于测量寿命。此外，太阳能电池将以反向角度放置，以阻挡反冲的光束状粒子。该特性将允许测量粒子门控伽马射线能谱，该能谱可用于采用反冲距离多普勒频移（RDDS）方法。此外，LaBr（Ce）探测器的安装将允许使用电子快速计时结合广义质心差（GCD）方法来测量寿命。这两种方法都是可靠的和建立的方法，以测量寿命在皮到纳秒范围内。利用所得到的寿命，可以得到简化的跃迁强度，以研究原子核的结构。第152和156Sm核位于所谓的“八极魔数”N = 88附近，因此是研究该区域八极变形的有趣案例。160,162Gd， 178Yb和182Hf同位素位于γ -软区附近，处于低洼的0+态。关于这些核的新数据将进一步改进作为玻尔-哈密顿量解析解的伽玛软模型。高质量同位素188W、194Os和200Pt表现出三轴性，特别是伽马柔软性。转变强度的减小是理解这一现象的重要标志。最后，所有这些结果将与基于平均场的质子-中子相互作用玻色子模型进行比较，以验证和理解其底层结构。

We plan to perform two-neutron transfer reactions in the 50 < Z < 82 region of the nuclear chart to investigate different nuclear structure phenomena. The nuclei of interest are 152Nd, 156Sm, 160,162Gd, 178Yb, 182Hf, 188W, 194Os and 200Pt which will be populated in a two-neutron transfer reaction using a 18O beam. The beam is provided by the Cologne 10 MV Tandem accelerator with the beam energy around the Coulomb barrier of the corresponding reaction. The Cologne Plunger spectrometer, equipped with 25 high purity germanium (HPGe) detectors and eight LaBr(Ce) detectors, will be used to measure lifetimes. Additionally, solar cells will be placed at backward angles to gate on the recoiling beam-like particles. This feature will allow to measure particle gated gamma-ray spectra which can be used to employ the recoil distance Doppler shift (RDDS) method. Further, the installation of LaBr(Ce) detectors will allow to measure lifetimes using the electronic fast timing in combination with the generalized centroid difference (GCD) method. Both methods are reliable and established method to measure lifetimes in the pico to nanosecond regime. With the resulting lifetimes, reduced transition strengths can be obtained to study the structure of the nuclei. The 152Nd and 156Sm nuclei lie close to the so-called "octupole magic" number N = 88 and are therefore interesting cases to study octupole deformation in this region. The 160,162Gd, 178Yb and 182Hf isotopes are located around the gamma-soft region with low-lying 0+ states. New data on these nuclei will further improve the gamma-soft model which is an analytical solution of the Bohr-Hamiltonian. The higher mass isotopes 188W, 194Os and 200Pt show evidences of triaxiality and especially gamma-softness. The reduced transition strength are important signatures to understand this phenomenon in this region. Lastly, all of these results will be compared to the mean field based proton-neutron interacting boson model to verify and understand the underlying structure.