三电子原子^(6)Li D线跃迁绝对频率的精密测量

Precise absolute frequency measurement of three-electron^(6)Li atom D-line transitions

在^(6)Li冷原子系综中,本团队发展了弱探测光和强本地光差拍探测的技术,在极低探测光功率密度的条件下(<10^(-3)饱和光强),实现了达到光子散粒噪声极限的光谱测量.基于高精度光学频率梳的频率稳定性传递链,将探测光锁到光梳上,精确测量了^(6)Li原子的D线跃迁频率,得到不确定度优于1 k Hz的^(6)Li D1线跃迁的绝对频率,比当前最高精度的测量提高了一个量级.2P能级精细结构劈裂和2P1/2能级超精细结构劈裂分别为10052.7804(18)和26.1031(14)MHz,与最近的相对论修正及量子电动力学修正的理论计算相符合.本团队的测量结果给更高精度的理论计算提供了实验基准,同时也有助于解决之前不同实验测量的差异.

We achieve the photon shot-noise limited optical spectroscopy of ^(6)Li cold atoms by developing a heterodyne detection technique,under the condition of extremely low optical power density(below 10^(-3)saturation intensity)of probe beam.We establish a transport chain of frequency stability based on an optical frequency comb,and achieve absolute frequencies measurement of D1lines with an uncertainty of about 1 k Hz,which is one order of magnitude more accurate than previous measurements.The 2P fine structure splitting of ^(6)Li and the hyperfine splitting of 2P1/2are 10052.7804(18)and26.1031(14)MHz,respectively,in agreement with recent theoretical calculations.Our results could provide a benchmark to test the theory at the higher precision and help to resolve large discrepancies among previous experiments.