Mm-wave absorption by two level systems in mesoscopic amorphous grains

Temperature dependent mm-wave (0.7-3 mm) absorption in mesoscopic amorphous silicate grains synthesized by sol-gel reaction has been measured between 1.2 and 15 K. These amorphous powders are precursors to forsterite (Mg2SiO4), enstatite (MgSiO3) and MgO . 2SiO(2). The measured bleaching of the absorption with increasing temperature characteristic of two level system behavior is observed in all cases and the results are compared with those obtained from bulk aerogel and soda-lime-silica glass. The weighted spectral density of two level states throughout this wavelength region is shown to be larger for all the silicate particles when compared with bulk soda-lime-silica glass.