Russwurm G M, Phillips B
ManTech Environmental Technology, Incorporated, 2 Triangle Drive, Research Triangle Park, North Carolina 27709, USA.
Appl Opt. 1999 Oct 20;38(30):6398-407. doi: 10.1364/ao.38.006398.
The response of a Fourier-transform infrared (FTIR) instrument to changes in absorbance is inherently nonlinear for a number of reasons. One is that the interferogram acquired by the FTIR is truncated and then apodized before further processing of the data is accomplished. A commonly used apodization function in open-path FTIR research is triangular apodization, and all the research presented here has been done with that function. We calculated a set of absorption spectra by using the HITRAN database, covering ranges in both concentration and temperature for water, ammonia, and methane. Plots of these data reveal nonlinear results. The commonly used analysis technique, classical least squares, assumes that the response is linear. We describe some of the effects of this nonlinearity and present ways to address these effects.
傅里叶变换红外（FTIR）仪器对吸光度变化的响应由于多种原因本质上是非线性的。一是FTIR采集的干涉图在完成数据的进一步处理之前会被截断然后进行变迹处理。开放路径FTIR研究中常用的变迹函数是三角变迹，这里展示的所有研究都是使用该函数完成的。我们利用HITRAN数据库计算了一组吸收光谱，涵盖了水、氨和甲烷在浓度和温度方面的范围。这些数据的图表显示出非线性结果。常用的分析技术，即经典最小二乘法，假定响应是线性的。我们描述了这种非线性的一些影响，并提出了解决这些影响的方法。
