We analyze laser cooling of two-electron atoms with three-level cascade transitions, involving the usual ¹S₀–¹P₁ cooling transition coupled to either ¹S₀ or ¹D₂ states. We numerically calculate minimum temperatures for the most abundant even isotopes of group II atoms and ytterbium (which lack hyperfine structure), derive general analytical expressions from a perturbative approach, and discuss the experimental implementation of the technique. Considered as an alternative 2nd stage technique to intercombination line cooling, three-level cooling is clearly advantageous for light elements, such as Mg and Ca, while for all elements provides much higher capture ranges, increasing the transfer efficiency from the 1st stage cooling, with faster cooling times and sub-Doppler temperatures.

我们分析了具有三级级联跃迁的两电子原子的激光冷却，包括通常的¹ S ₀ – ¹ P ₁冷却跃迁耦合到¹ S ₀或¹ D ₂状态。我们通过数值计算了最丰富的 II 族原子和镱（缺乏超精细结构）的偶数同位素的最低温度，从微扰方法推导出一般分析表达式，并讨论了该技术的实验实施。作为组合线冷却的替代第二阶段技术，三级冷却显然有利于轻元素，如镁和钙，而对于所有元素，提供更高的捕获范围，提高第一阶段冷却的传递效率，与更快的冷却时间和亚多普勒温度。