气体的光谱吸收率是Lambert-Beer定律对气体进行定性定量分析的重要依据, 光谱吸收率积分值是描述气体吸收特性的一个重要参量。 根据所测气体的吸收光谱图, 通过从HITRAN数据库中查询得到所需数据, 选择其中一条吸收光谱, 计算出光谱吸收率在频域上的积分值, 然后把积分值代入Lambert-Beer定律便可以求出所测气体的浓度值。 计算光谱吸收率的积分值, 能够避开复杂的线型函数的计算, 不需要通过标准气体进行校准, 从而更加简捷、 快速地求出气体浓度值。 鉴于温度变化会引起相应的压强的变化, 同时在压强不随温度变化以及压强随温度共同变化这两种情况下, 对光谱吸收率积分值随温度的变化规律进行了研究。 总结出在这两种情况下, 光谱吸收率在频域上的积分值总是随着温度的增加而增加, 当增加到一定温度时, 光谱吸收率在频域上的积分值随着温度的增加而减小, 最后趋于稳定, 但是两种情况下光谱吸收率积分值变化趋势的范围有所不同。 最后通过实验验证计算光谱吸收率在频域内的积分值时需要同时考虑温度的变化以及温度导致的相应的压强的变化, 此时吸收率积分值相对误差约为1%; 只考虑温度的变化而不考虑压强随温度的变化, 吸收率积分值的相对误差值大于1%而且逐渐变大。 研究温度对光谱吸收率积分值的影响, 可以在使用光谱吸收率积分值计算气体浓度时, 选择合适的温度范围即更稳定的吸收区, 从而减少温度对测量结果带来的误差。

The absorptance spectrum of a gas is the basis for the qualitative and quantitative analysis of the gas by the law of the Lambert-Beer. The integral value of the absorptance spectrum is an important parameter to describe the characteristics of the gas absorption. Based on the measured absorptance spectrum of a gas, we collected the required data from the database of HITRAN, and chose one of the spectral lines and calculated the integral value of the absorptance spectrum in the frequency domain, and then substituted the integral value into Lambert-Beer’s law to obtain the concentration of the detected gas. By calculating the integral value of the absorptance spectrum we can avoid the more complicated calculation of the spectral line function and a series of standard gases for calibration, so the gas concentration measurement will be simpler and faster. We studied the changing trends of the integral values of the absorptance spectrums versus temperature. Since temperature variation would cause the corresponding variation in pressure, we studied the changing trends of the integral values of the absorptance spectrums versus both the pressure not changed with temperature and changed with the temperature variation. Based on the two cases, we found that the integral values of the absorptance spectrums both would firstly increase, then decrease, and finally stabilize with temperature increasing, but the ranges of specific changing trend were different in the two cases. In the experiments, we found that the relative errors of the integrated values of the absorptance spectrum were much higher than 1% and still increased with temperature when we only considered the change of temperature and completely ignored the pressure affected by the temperature variation, and the relative errors of the integrated values of the absorptance spectrum were almost constant at about only 1% when we considered that the pressure were affected by the temperature variation. As the integral value of the absorptance spectrum varied with temperature and the calculating error for the integral value fluctuates with ranges of temperature, in the gas measurement when we used integral values of the absorptance spectrum, we should select a suitable temperature range, that is, a more stable absorption range to reduce error caused by the temperature variation and obtain a more accurate measurement result.