利用光腔衰荡法测量吸收系数时,光在吸收介质中的传播速度和空腔是不同的,这种区别导致测量精度在一定程度上受到影响。为了考察吸收系数的测量精度受光速变化的影响程度,进行了相关的分析和推导,并根据实验及部分文献提供的数据进行了数值计算,得到了忽略光速变化将导致测量结果偏小的结论,偏差值与腔镜反射率有关。当腔镜反射率达到99.99%时,就有必要考虑该因素的影响,除非实际测量中存在其它因素使测量精度远不能达到最高值。

The difference of the light speed in absorption medium and vacuum affects the precision when the absorption coefficient is measured by use of CRDS. This paper made the discussion and illation in order to study the influence of light speed on the precision of CRDS in measurement of the absorption coefficient. A numerical calculation has been done according to the data provided by the experiments and part of scientific literature. The conclusion is that neglecting the change of light speed would lead to the smaller measuring value. The deviation is connected with the mirror’s reflectivity. The influence of light speed should be considered when the reflectivity is 99.99% unless other factors make the precision of absorption measurement for lower than the maximal value.