Knowledge Bank

“Infrared and Raman spectra have been measured for the high $(Td2)$ and low $(Vh16)$ temperature forms of $NH4ClO4,NDdClO4$, and $KClO4$. Raman polarization measurements have been made on a single crystal of low $NH4ClO4$. Interpretations by previous workers in terms of tetrahedral selection rules are adequate to explain only the gross features of the spectra of these crystals. In the present work the data have been analyzed using the relevant factor groups. The results will be discussed in terms of the crystal structures and interionic forces and the question of free or restricted rotation will be examined.”