Observation of the radiative decay of the ^229Th nuclear clock isomer
Observation of the radiative decay of the ^229Th nuclear clock isomer
复制标题
^229Th核钟异构体辐射衰变的观测
作者：
S. Kraemer;J. Moens;M. Athanasakis;S. Bara;K. Beeks;P. Chhetri;K. Chrysalidis;A. Claessens;T. Cocolios;J. M. Correia;H. Witte;R. Ferrer;S. Geldhof;R. Heinke;Niyusha Hosseini;M. Huyse;Ulli Köster;Y. Kudryavtsev;M. Laatiaoui;R. Lică;G. Magchiels;V. Manea;C. Merckling;Lino M. C. Pereira;S. Raeder;T. Schumm;S. Sels;P. Thirolf;S. M. Tunhuma;Paul Van den Bergh;P. Van Duppen;A. Vantomme;M. Verlinde;R. Villarreal;U. Wahl
作者报告了钍 229 (^229mTh) 中低能异构体的辐射衰变，这对未来核钟的设计产生了影响，并简化了对原子核直接激光激发的研究。放射性核素钍 229 的异构体具有极低的激发能量，可以直接用激光操纵核态。它是下一代光学时钟的主要候选者之一^ 1 – 3 。该核钟将成为精确测试基础物理的独特工具^ 4 – 9 。尽管这种非同寻常的核态存在的间接实验证据要早得多^ 10 ，但存在的证据直到最近才通过观察异构体的电子转换衰变来提供^ 11 。测量了异构体的激发能、核自旋和电磁矩、电子转换寿命和异构体的精化能量^ 12 – 16 。尽管最近取得了进展，但异构体的辐射衰变（核钟发展的关键因素）仍未被观察到。在这里，我们报告了在钍 229 (^229mTh) 中检测到这种低能异构体的辐射衰变。通过在 CERN 的 ISOLDE 设施中对纳入大带隙 CaF_2 和 MgF_2 晶体的 ^229mTh 进行真空紫外光谱，测量到 8.338(24) eV 的光子，与最近的测量结果一致^ 14 – 16，并且不确定性降低了七倍。嵌入MgF_2中的^229mTh的半衰期确定为670(102) s。大带隙晶体中辐射衰变的观察对于未来核钟的设计具有重要影响，并且能量不确定性的改善简化了对原子核直接激光激发的研究。
The authors report on the radiative decay of a low-energy isomer in thorium-229 (^229mTh), which has consequences for the design of a future nuclear clock and eases the search for direct laser excitation of the atomic nucleus. The radionuclide thorium-229 features an isomer with an exceptionally low excitation energy that enables direct laser manipulation of nuclear states. It constitutes one of the leading candidates for use in next-generation optical clocks^ 1 – 3 . This nuclear clock will be a unique tool for precise tests of fundamental physics^ 4 – 9 . Whereas indirect experimental evidence for the existence of such an extraordinary nuclear state is substantially older^ 10 , the proof of existence has been delivered only recently by observing the isomer’s electron conversion decay^ 11 . The isomer’s excitation energy, nuclear spin and electromagnetic moments, the electron conversion lifetime and a refined energy of the isomer have been measured^ 12 – 16 . In spite of recent progress, the isomer’s radiative decay, a key ingredient for the development of a nuclear clock, remained unobserved. Here, we report the detection of the radiative decay of this low-energy isomer in thorium-229 (^229mTh). By performing vacuum-ultraviolet spectroscopy of ^229mTh incorporated into large-bandgap CaF_2 and MgF_2 crystals at the ISOLDE facility at CERN, photons of 8.338(24) eV are measured, in agreement with recent measurements^ 14 – 16 and the uncertainty is decreased by a factor of seven. The half-life of ^229mTh embedded in MgF_2 is determined to be 670(102) s. The observation of the radiative decay in a large-bandgap crystal has important consequences for the design of a future nuclear clock and the improved uncertainty of the energy eases the search for direct laser excitation of the atomic nucleus.
影响因子：
2.4
作者：
P. Thirolf;B. Seiferle;Lars der Wense
通讯作者：
P. Thirolf;B. Seiferle;Lars der Wense
影响因子：
64.8
作者：
Seiferle, Benedict;von der Wense, Lars;Thirolf, Peter G.
通讯作者：
Thirolf, Peter G.