Missing Fe: hydrogenated iron nanoparticles
  Although it was found that the FeH lines exist in the spectra of some stars,
none of the spectral features in the ISM have been assigned to this molecule.
We suggest that iron atoms interact with hydrogen and produce Fe-H
nanoparticles which sometimes contain many H atoms. We calculate infrared
spectra of hydrogenated iron nanoparticles using density functional theory
methods and find broad, overlapping bands. Desorption of H2 could induce
spinning of these small Fe-H dust grains. Some of hydrogenated iron
nanoparticles posses magnetic and electric moments and should interact with
electromagnetic fields in the ISM. Fe_nH_m nanoparticles could contribute to
the polarization of the ISM and the anomalous microwave emission. We discuss
the conditions required to form FeH and Fe_nH_m in the ISM.
