Title: Direct measurement of the 3P0 clock state natural lifetime in 87Sr Show Chinese title

Title: 87Sr的3P0钟态自然寿命的直接测量

Abstract: Optical lattice clocks based on the narrow (5s2)1S0 - (5s5p)3P0 transition in neutral strontium (Sr) are among the most precise and accurate measurement devices in existence. Although this transition is completely forbidden by selection rules, state mixing from the hyperfine interaction in 87Sr provides a weakly allowed transition that can be coherently driven with practical clock laser intensities. While the coherent interrogation times of optical clocks are typically set by the linewidth of the probe laser, this limitation can be overcome in synchronous differential comparisons between ensembles. In such measurements the natural lifetime of the 1S0-3P0 clock transition becomes the fundamental limiting factor to the duration of a single run of the experiment. However, a direct measurement of the decay rate of the clock excited state is quite challenging due to the competing effects of other loss channels such as Raman scattering, inelastic collisions and atom-loss due to background gas. In this work, we monitor the decay of Sr atoms trapped in an optical lattice and initialized in the 3P0 state. By making measurements of high and low density ensembles of both 87Sr and 88Sr across varying lattice trap depths, we isolate radiative decay, which accounts for a significant fraction of the observed decays at low depths. We obtain a natural radiative decay lifetime of 167(+79/-40) s for the 3P0 clock state in 87Sr, a value that is consistent with previously reported measurements and theoretical predictions. We also introduce an additional measurement scheme that involves repeated measurements of the ground state population within a single experimental sequence, validating our model and the consistency of the measured rates. Show Chinese abstract

Abstract: 基于中性锶（Sr）的窄(5s2)1S0 - (5s5p)3P0跃迁的光学晶格钟是目前最精确和准确的测量装置之一。 尽管该跃迁根据选择规则是完全禁戒的，但87Sr中的超精细相互作用导致的状态混合提供了一个弱允许的跃迁，可以用实际的钟激光强度进行相干驱动。 虽然光学钟的相干探测时间通常由探测激光的线宽决定，但在集合体之间的同步差分比较中可以克服这一限制。 在这样的测量中，1S0-3P0钟跃迁的自然寿命成为实验单次运行持续时间的基本限制因素。 然而，由于其他损耗通道的竞争效应，如拉曼散射、非弹性碰撞和背景气体引起的原子损失，直接测量钟激发态的衰减率非常具有挑战性。 在本工作中，我们监测了被俘获在光学晶格中并初始化为3P0态的Sr原子的衰减。 通过在不同晶格陷阱深度下对87Sr和88Sr的高密度和低密度集合体进行测量，我们分离出辐射衰减，这在低深度下占观察到的衰减的显著部分。 我们获得了87Sr中3P0钟态的自然辐射衰减寿命为167(+79/-40)秒，该值与之前报告的测量结果和理论预测一致。 我们还引入了一种额外的测量方案，涉及在单一实验序列中重复测量基态粒子数，验证了我们的模型以及测量速率的一致性。