The authors report spectroscopic observations (2.4 - 3.6 μm) of BN, IRc 2, 3, and 4, and three scattering locations in the KL reflection nebula. A previous report (Knacke et al., 1982) of a 2.97 μm spectral feature in the BN object is not confirmed in the new data. The 2.97 μm feature is observed in sources in the KL nebula, and the spectrum is distorted by a nearby hydrogen line. All the spectra are dominated by absorption along the radiation path, making scattering effects difficult to separate. Scattering could broaden the 3.1 μm interstellar-ice feature, but the effects appear to be small. Except for a long-wavelength wing, the spectra can be modeled reasonably well with core-mantle, silicate-water-ice grains. The wing position and intensity indicate bands of C-H groups or ammonia-ice mixtures.
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Knacke et al. (1987) studied this question.