Lifetimes of low-lying excited states in the $\nu i_{13/2^{+}}$ bands of the neutron-deficient osmium isotopes ^169,171,173Os have been measured for the first time using the recoil-distance Doppler shift and recoil-isomer tagging techniques. An unusually low value is observed for the ratio $B(E2;21/2^{+}\to 17/2^{+})/B(E2;17/2^{+}\to 13/2^{+})$ in ¹⁶⁹Os, similar to the “anomalously” low values of the ratio $B(E2;4_1^{+}\to 2_1^{+})/B(E2;2_1^{+}\to 0_{\mathrm{gs}}^{+})$ previously observed in several transitional rare-earth nuclides with even numbers of neutrons and protons, including the neighbouring ^168,170Os. Furthermore, the evolution of $B(E2;21/2^{+}\to 17/2^{+})/B(E2;17/2^{+}\to 13/2^{+})$ with increasing neutron number in the odd-mass isotopic chain ^169,171,173Os is observed to follow the same trend as observed previously in the even-even Os isotopes. These findings indicate that the possible quantum phase transition from a seniority conserving structure to a collective regime as a function of neutron number suggested for the even-even systems is maintained in these odd-mass osmium nuclei, with the odd valence neutron merely acting as a “spectator”. As for the even-even nuclei, the phenomenon is highly unexpected for nuclei that are not situated near closed shells.

低激发态的寿命 $\nu {\mathrm{一世}}_{13/2^{+}}$使用反冲距离多普勒频移和反冲异构体标记技术首次测量了中子缺陷锇同位素^169,171,173 Os 的谱带。观察到该比率异常低的值$乙(乙2;21/2^{+}\to 17/2^{+})/乙(乙2;17/2^{+}\to 13/2^{+})$在^{169 个}Os 中，类似于比率的“异常”低值$乙(乙2;4_1^{+}\to 2_1^{+})/乙(乙2;2_1^{+}\to 0_{\mathrm{GS}}^{+})$之前在几个具有偶数中子和质子的过渡稀土核素中观察到，包括邻近的^168,170 Os。此外，进化的$乙(乙2;21/2^{+}\to 17/2^{+})/乙(乙2;17/2^{+}\to 13/2^{+})$随着奇质量同位素链中中子数的增加，观察到^169,171,173 Os 遵循与之前在偶偶 Os 同位素中观察到的相同趋势。这些发现表明，在这些奇质量锇原子核中，作为偶偶系统建议的中子数的函数，可能存在从资历守恒结构到集体制度的量子相变，而奇价中子仅作为“观众”。至于偶偶核，这种现象对于不在封闭壳附近的核来说是非常出乎意料的。