IMPROVED DETECTION LIMITS IN FOURIER-TRANSFORM SPECTROSCOPY FROM A MAXIMUM-ENTROPY APPROACH TO BASE-LINE ESTIMATION

A new method for baseline estimation and correction in gas phase Fouri er transform (FT) absorption spectra based on a maximum entropy approa ch is described. In this novel method, a smoothly varying baseline fun ction is determined directly from the observed spectra by separating b aseline and signal information on the basis of line width, Baselines o f arbitrary complexity may be determined provided there is a differenc e of at least a factor of 5 in line width between the signal and basel ine features and there are no discontinuities in the baseline, As base line drift is often much larger than the noise in FT spectroscopy, sig nificantly improved detection limits are obtained using this method fo r the quantitative analysis of trace gases, Even in the absence of bas eline drift, the use of an accurate noise-free baseline function will always lead to some improvement in the detection limits, The quantitat ive results are shown to be insensitive to input parameters over a wid e range.