Nickerson Brenden S, Pimon Martin, Bilous Pavlo V, Gugler Johannes, Beeks Kjeld, Sikorsky Tomas, Mohn Peter, Schumm Thorsten, Pálffy Adriana
Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany.
Center for Computational Material Science, Technische Universität Wien, 1040 Vienna, Austria.
Phys Rev Lett. 2020 Jul 17;125(3):032501. doi: 10.1103/PhysRevLett.125.032501.
When Th nuclei are doped in CaF_{2} crystals, a set of electronic defect states appear in the crystal band gap which would otherwise provide complete transparency to vacuum-ultraviolet radiation. The coupling of these defect states to the 8 eV ^{229m}Th nuclear isomer in the CaF_{2} crystal is investigated theoretically. We show that although previously viewed as a nuisance, the defect states provide a starting point for nuclear excitation via electronic bridge mechanisms involving stimulated emission or absorption using an optical laser. The rates of these processes are at least 2 orders of magnitude larger than direct photoexcitation of the isomeric state using available light sources. The nuclear isomer population can also undergo quenching when triggered by the reverse mechanism, leading to a fast and controlled decay via the electronic shell. These findings are relevant for a possible solid-state nuclear clock based on the ^{229m}Th isomeric transition.
当钍核掺杂在CaF₂晶体中时，晶体带隙中会出现一组电子缺陷态，否则该晶体对真空紫外辐射是完全透明的。本文从理论上研究了这些缺陷态与CaF₂晶体中8 eV的²²⁹mTh核异构体之间的耦合。我们表明，尽管这些缺陷态以前被视为一种干扰，但它们通过涉及使用光学激光的受激发射或吸收的电子桥机制，为核激发提供了一个起点。这些过程的速率比使用现有光源对异构体状态进行直接光激发的速率至少大2个数量级。当由反向机制触发时，核异构体粒子数也会发生猝灭，从而通过电子壳层实现快速且可控的衰变。这些发现与基于²²⁹mTh异构体跃迁的可能的固态核钟相关。
