The following is an abstract for the selected article. A PDF download of the full text of this article is available here. Members may download full texts at no charge. Non-members may be charged a small fee for certain articles.
Raman Spectra of Solid (NH4)2CrO4 and (ND4)2CrO4 Obtained by a Rotating Cell Technique
Volume 30, Number 2 (April 1976) Page 187-190
Carter, Robert L.; O'Hare, L. Kevin
The Raman spectra of polycrystalline (NH4)2CrO4 and (ND4)2CrO4 have been obtained by a sample rotation technique where the uncompressed solid is contained in a glass cylindrical cell. The apparatus is a commerically available sample rotator for liquids, which was modified for the described solid sampling technique. The Raman spectra of (NH4)2CrO4 and (ND4)2CrO4 are discussed in relation to their uniquely monoclinic structure, in contrast to the β-K2SO4 structure found for (NH4)2SO4 and many alkali metal chromates and sulfates. The hydrogen bonding in (NH4)2CrO4 is described, and its role in determining both the structure and the Raman spectra is discussed. The data suggest a barrier to NH4+ rotation of approximately 3.70 kcal/mol, indicating that the ammonium ions are not freely rotating on the time scale of the Raman experiment (10−13 sec).