DOAS谱线波长配准存在的问题及解决方法

A Method for Resolving the Spectra Shift and Squeeze in Differential Optical Absorption Spectroscopy

由于系统光学部分的干扰(衍射光栅的不完善和光谱仪散射光)的存在,引起测量谱线的抖动.这将在差分光学吸收光谱(DOAS)谱线信号中产生人为结构,这些结构与污染气体的特征差分吸收区很难区分开,这种噪声的显著特点是在一段时间内是稳定的,因此它的值不能通过通常的时间平均消除掉.然而,当灯光源直接照射接收系统(不通过空气光路)时,灯信号中的人为结构与从实测光路信号谱中的相似结构具有很大的相关性.因此应用实测光路信号除以灯谱信号在很大的程度上消除噪声的影响.但是采用该方法时,若所使用的光源谱线结构起伏较大,对灯谱和信号谱的坐标一致性要求将非常高,否则对吸收光谱的计算会带来更多的影响.本文通过对该问题的研究提出了两种解决方案,通过实验证明可以有效地减小谱线偏移带来的分析误差.

The interferences owing to the defects of the grating and the stray light in the spectrometer of DOAS system cause the extra .spectral structures, which are difficult to lie distinguished from the absorption structures of the flue gas. These structures can not be removed by averaging the spectra, due to their relative stability in certain time periods. The lamp spectra taken before the light going to the polluted flue gas reflects the same instrumental structures as the spectra of the flue gas. Therefore it is very useful to reduce the noise from the optical components by dividing the lamp spectra. It is mentioned that in this case both spectra of the lamp and the flue gas should match to each other exactly in the wavelength. In order to solve these problems, two methods have been presented in this paper. It has been shown that the error of retriving the concen tration have been reduced in the experiment.