基于仪器线型订正的开放光程FTIR测量中的水汽谱在线扣除方法

水汽吸收分布于整个中红外波段，它的存在干扰红外光谱的定量分析。文章介绍了一种从傅里叶变换红外光谱仪的测量数据中扣除水汽干扰信号的新方法。该方法首先通过气象参数测量获得气压、温度和相对湿度，结合HITRAN数据库中提供的水汽线强、自展宽、空气展宽等参数，使用逐线积分方法计算出高分辨率水汽吸收谱，再通过仪器线型订正，合成出与仪器分辨率相匹配的水汽谱，将其作为干扰组分直接从测量所得到的含有水汽的混合光谱中扣除。对开放光程FTIR系统的实测数据的分析结果表明，使用该方法可以有效消除水汽干扰，扣除后的光谱包含待测组分的吸收特征和噪声。在开放光程FTIR等无法使用干燥设备去水的观测条件下，使用该方法可以达到较理想的水汽扣除效果。

A Method of Eliminating the Water Vapor Interference Simultaneously in Open Path FTIR Measurement by Instrumental Line Shape Correction

Water vapor absorption,which exists in mid-infrared region,is an interferential element for infrared spectra analysis.A new method,which can be used to eliminate the water vapor interference in FTIR measurement,is presented.To calculate the high resolution absorbance of water vapor,a fast line by line method which computed with the HITRAN database(eg.line strength,self broadening, air broadening,etc) and meteorological parameters(eg.temperature,pressure,and relative humidity) was used.After convolving with Instrumental line shape(eg.divergence angle,resolution,etc),the absorbance of water vapor was then transferred from high resolution to low resolution,which matched the instrumental parameters.After the acquirement of water vapor absorbance spectrum, it will be subtracted from the measured spectrum to calculate the spectrum with the water vapor was eliminated.In the present work,analysis of measured data from open path FTIR is described.Only the absorbing character and noise was left in the spectrum after eliminating the water vapor interference.Consequently,this method has an ideal effect on water vapor elimination when there is no dryer can be used,especially in the case of open path FTIR measurement.