INFRARED SPECTRUM AND PHASE TRANSITIONS IN AMMONIUM THIOCYANATE BELOW ROOM TEMPERATURE
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Date
1963
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Ohio State University
Abstract
“Sublimed films of $NH_{4}NCS$ and of $ND_{4}NCS$ have been examined over a range of temperatures with an infrared grating spectrometer through the fundamental regions of the ammonium and the thioicyanate ions; partially deuterated material has also been studied. In the phase which is stable at room temperature and which, once formed, persists down to liquid $N_{2}$ temperatures, details of the spectrum are consistent with the site group splittings expected on the basis of the $C_{2h}^{5}$ tetra-molecular unit cell. An apparently metastable phase has also been observed which yields- a larger number of components for each $NH_{4}^{+}$ and $NCS^{-}$ fundamental. A detailed potential function for the ammonium ion has been evaluated, the results being expressed in terms of the compliance matrix, $C = F^{-1}$, where F is the matrix of the force constants.”
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Author Institution: Department of Chemistry, Oregon State University