APPLICATION OF DETECTOR NONLINEARITY CORRECTION FOR FT-IR SPECTROMETRIC GAS-ANALYSIS OF SF6 SAMPLES

Fourier-transform infrared spectroscopy can achieve the low spectral n oise level necessary for trace analysis. In the midinfrared a photocon ductive HgCdTe detector is routinely used, which suffers From a substa ntial non-linear response for high radiation flux such as found when r ecording the interferogram centre-burst. The photometric accuracy, clo se to detector cut-off, is thereby dramatically reduced for strongly a bsorbing samples, and the line shapes can be seriously influenced by p hase errors. The effects on the spectra of gaseous SF6, and the improv ements gained by software correction are presented.