自共轭$^{76}_{38}$ Sr $_{38}$中相互增强集体性的观察
Observation of mutually enhanced collectivity in self-conjugate $^{76}_{38}$Sr$_{38}$
摘要：
使用$γ$射线线形方法和两步核子交换反应的独特组合测量了缺中子$^{76,78}$ Sr同位素中前2个$^{+}$态的寿命。2个$^{+}$状态的跃迁速率被确定为$B$（E2; 2 $^{+}$ $\to 0^{+}$）= 2220（270）e $^{2}$ fm $^{4}$（对于$^{76}$ Sr）和1800（250）e $^{2}$ fm $^{4}$（对于$^{78}$ Sr），对应于大变形，对于$^{76}$ Sr，$β_2$ = 0.45（3），对于0.40（3），对于$^{78}$ Sr。本数据提供了在$N$ = $Z$ = 38处发生的相互增强的集体性的实验证据。激发能和$B$（E2）值的系统行为表明了$^{76}$ Sr中形状共存的特征，表征$^{76}$ Sr为具有异常降低的$E$（4 $^{+}$）/ $E$（2 $^{+}$）比的最变形的核之一。
英文摘要：
The lifetimes of the first 2$^{+}$ states in the neutron-deficient $^{76,78}$Sr isotopes were measured using a unique combination of the $γ$-ray line-shape method and two-step nucleon exchange reactions at intermediate energies. The transition rates for the 2$^{+}$ states were determined to be $B$(E2;2$^{+}$$\to 0^{+}$) = 2220(270) e$^{2}$fm$^{4}$ for $^{76}$Sr and 1800(250) e$^{2}$fm$^{4}$ for $^{78}$Sr, corresponding to large deformation of $β_2$ = 0.45(3) for $^{76}$Sr and 0.40(3) for $^{78}$Sr. The present data provide experimental evidence for mutually enhanced collectivity that occurs at $N$ = $Z$ = 38. The systematic behavior of the excitation energies and $B$(E2) values indicates a signature of shape coexistence in $^{76}$Sr, characterizing $^{76}$Sr as one of most deformed nuclei with an unusually reduced $E$(4$^{+}$)/$E$(2$^{+}$) ratio.
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