Interstellar Extinction by Quartz Grains

Abstract

KNACKE1 has pointed out that quartz particles possess strong absorption bands at λ∼10µ. Although these features occur in the spectral region 3–10µ, where Johnson2 has found humps in interstellar extinction curves, by itself this cannot be taken as indicating a silica component in the interstellar grains. It has already been pointed out3 that impurities in any solid with a Debye frequency close to that of graphite would give optically active lattice bands at λ∼10µ*. Further evidence would be necessary before quartz could be considered as a serious alternative to interstellar graphite grains.