Example extractions of the profile of the 4.1 µm HDO O-D stretching mode from the H₂O combination mode in 0.4% HDO:H₂O laboratory spectra (top: amorphous; bottom: crystalline). The laboratory data (already baseline corrected) is plotted in black, the local continuum is plotted in dashed red, and the smoothed and extracted profile is plotted in green. The red shading indicates the wavelengths used to define the local continuum, and the green shading indicates the integrated area used to derive the apparent band strengths.