Lifetime measurement of neutron-rich even-even molybdenum isotopes
Lifetime measurement of neutron-rich even-even molybdenum isotopes
复制标题
富中子偶偶钼同位素的寿命测量
DOI：
10.1103/physrevc.95.034320
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发表时间：
2017
影响因子：
3.1
通讯作者：
et al.
中科院分区：
文献类型：
--
作者：
D. Ralet;S. Pietri;M.L. Cortes;et al.
背景：在富中子质量区，各种理论模型预测了快速的形状变化作为核子数的函数，以及共存的长形，扁球形和三轴形状。钼同位素激发能级的寿命测量允许确定过渡四极矩，这反过来又提供了关于预测的形状changes.Purpose的结构信息：本论文报告的实验装置，方法，允许一个测量激发态的钼同位素从massup到质量的寿命，并获得的结果。方法：感兴趣的同位素通过中子的二次敲除反应填充，由GSI碎片分离器在相对论束流能量下分离和鉴定，并由灵敏的PreSPEC-AGATA实验装置检测的富核。后者包括Lund-York-科隆量热计，用于识别、跟踪和测量抛射体的速度，以及AGATA，一种位置敏感分段HPGe探测器阵列，用于确定射线的相互作用位置，从而实现精确的多普勒校正。使用已知能量的α-射线跃迁的多普勒校正后的能量的系统偏移，用多普勒偏移衰减方法的相对论版本确定寿命。这种相对论多普勒频移衰减方法允许的平均寿命从2到250 ps.Results的测定：甚至，甚至钼同位素从mastowere研究。观察到基态带中低激发态的衰变。特别是，两个平均寿命测量的第一次：ps的状态和ps的状态。结论：减少过渡强度，从在本实验中测得的寿命计算，相比超越平均场计算，表明钼同位素链中的一个逐渐的形状过渡时，从到达到最大值。跃迁几率降低，这可能与计算表明的明显的三轴形状有关。
Background:In the neutron-richmass region, rapid shape changes as a function of nucleon number as well as coexistence of prolate, oblate, and triaxial shapes are predicted by various theoretical models. Lifetime measurements of excited levels in the molybdenum isotopes allow the determination of transitional quadrupole moments, which in turn provides structural information regarding the predicted shape change.Purpose:The present paper reports on the experimental setup, the method that allowed one to measure the lifetimes of excited states in even-even molybdenum isotopes from massup to mass, and the results that were obtained.Method:The isotopes of interest were populated by secondary knock-out reaction of neutron-rich nuclei separated and identified by the GSI fragment separator at relativistic beam energies and detected by the sensitive PreSPEC-AGATA experimental setup. The latter included the Lund-York-Cologne calorimeter for identification, tracking, and velocity measurement of ejectiles, and AGATA, an array of position sensitive segmented HPGe detectors, used to determine the interaction positions of theray enabling a precise Doppler correction. The lifetimes were determined with a relativistic version of the Doppler-shift-attenuation method using the systematic shift of the energy after Doppler correction of a-ray transition with a known energy. This relativistic Doppler-shift-attenuation method allowed the determination of mean lifetimes from 2 to 250 ps.Results:Even-even molybdenum isotopes from masstowere studied. The decays of the low-lying states in the ground-state band were observed. In particular, two mean lifetimes were measured for the first time:ps for thestate ofandps for thestate of.Conclusions:The reduced transition strengths, calculated from lifetimes measured in this experiment, compared to beyond-mean-field calculations, indicate a gradual shape transition in the chain of molybdenum isotopes when going fromtowith a maximum reached at. The transition probabilities decrease forwhich may be related to its well-pronounced triaxial shape indicated by the calculations.