利用缀饰原子方法研究了激光同位素分离涉及的一个四能级系统的布居转移过程，发现了类似于三能级系统的布居囚禁态。在此基础上分析了光泵浦过程的布居囚禁现象，提出一种能够利用基态布居及亚稳态热布居的高效率光泵浦方法并以分离铀原子为例说明该方法的优越性。

The population transfer of a four level system coupled with three lasers is investigated in terms fo dressed atom model, and two dressed states are found to be similar to the so called trapped state in three level system. The population trapping in the four level system is analyzed and an optical pumping method with high efficiency is proposed for pouplation transfer from both ground state and metastable state. The superiority of the method is demonstrated numerically when it is used in U isotopes separation.