建立了以Rb-Ar混合气体为增益介质的四能级准分子宽带泵浦碱金属激光器(XPAL)含时速率方程模型, 计算得到了运转过程各能级粒子数和腔内激光强度随时间的变化曲线。结果表明:XPAL的阈值泵浦强度很高, 泵浦源谱宽与吸收线宽匹配不能达到提高吸收效率、降低阈值的目的；在泵浦功率一定的条件下,增加介质长度和温度可以提高吸收效率, 但将降低单位体积泵浦速率；XPAL成功的关键在于实现有效的泵浦吸收。

The time-depended rate equation model of four-level excimer pumped alkali laser (XPAL) is established, and the population of each level and laser intensity in cavities varying with time are calculated. The result is compared with experiments, and it indicates that the threshold pump intensity of XPALs is too high. Matching the spectral width of pump to the width of absorption could not improve the absorption efficiency, neither could law down the pump threshold. When the pump intensity keeps the same, the absorption efficiency could be improved by either increasing the length of gain medium or the temperature, but the pump rate in unit volume decreases. The key to success of XPALs is to achieve effective pump absorption.