${\mathrm{LiSrAlF}}_6$ crystals doped with ${}^{229}\mathrm{Th}$ are used in a laser-based search for the nuclear isomeric transition. Two spectroscopic features near the nuclear transition energy are observed. The first is a broad excitation feature that produces redshifted fluorescence that decays with a timescale of a few seconds. The second is a narrow, laser-linewidth-limited spectral feature at $148.38219(4{)}_{\mathrm{stat}}(20{)}_{\mathrm{sys}}\mathrm{nm}$ [$2020407.3(5{)}_{\mathrm{stat}}(30{)}_{\mathrm{sys}}\mathrm{GHz}$] that decays with a lifetime of $568(13{)}_{\mathrm{stat}}(20{)}_{\mathrm{sys}}\mathrm{s}$. This feature is assigned to the excitation of the ${}^{229}\mathrm{Th}$ nuclear isomeric state, whose energy is found to be $8.355733(2{)}_{\mathrm{stat}}(10{)}_{\mathrm{sys}}\mathrm{eV}$ in ${}^{229}\mathrm{Th}:{\mathrm{LiSrAlF}}_6$.

中文翻译：

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固态宿主中 Th229 核异构体转变的激光激发


掺杂有 ${}^{229}\mathrm{Th}$ 的 ${\mathrm{LiSrAlF}}_6$ 晶体用于基于激光的核异构转变搜索。观察到核跃迁能附近的两个光谱特征。第一个是广泛的激发特征，可产生红移荧光，并在几秒的时间尺度内衰减。第二个是 $148.38219(4{)}_{\mathrm{stat}}(20{)}_{\mathrm{sys}}\mathrm{nm}$ [ $2020407.3(5{)}_{\mathrm{stat}}(30{)}_{\mathrm{sys}}\mathrm{GHz}$ ] 处的窄激光线宽限制光谱特征，其寿命为 $568(13{)}_{\mathrm{stat}}(20{)}_{\mathrm{sys}}\mathrm{s}$ 衰减。该特征归因于 ${}^{229}\mathrm{Th}$ 核异构态的激发，其能量被发现为 ${}^{229}\mathrm{Th}:{\mathrm{LiSrAlF}}_6$ 中的 $8.355733(2{)}_{\mathrm{stat}}(10{)}_{\mathrm{sys}}\mathrm{eV}$ 。