Elimination of Baseline Variations from a Recorded Spectrum by Ultra-Low Frequency Filtering

A technique for the elimination of baseline variation is discussed and illustrated. The method involves ultra-low frequency filtering in the frequency domain (transform space) and is illustrated by applying it to several diode laser spectra of C 2 H 6 (ethane). In the examples presented, the technique eliminates the effects of diode laser output energy variations as a particular mode is scanned. This technique may be especially valuable for diode laser spectroscopy where a multipass cell is used and where the cell cannot readily be removed from the beam to obtain a background scan. The technique should be applicable to baseline variation problems in general.