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Raman active torsion‐libration overtones in crystalline N 2 H 6 Cl 2 and N 2 H 6 Br 2
Author(s) -
Ratcliffe C. I.,
Sherman W. F.,
Wilkinson G. R.
Publication year - 1981
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250110309
Subject(s) - libration (molecule) , raman spectroscopy , chemistry , bromide , activation energy , chloride , internal rotation , torsion (gastropod) , analytical chemistry (journal) , inorganic chemistry , physics , optics , organic chemistry , medicine , geometry , point (geometry) , surgery , mechanical engineering , engineering , mathematics
Raman active torsion‐libration fundamentals and overtones have been observed in crystals of N 2 H 6 Cl 2 and N 2 H 6 Br 2 . The temperature dependences of these modes have been followed between liquid nitrogen and room temperatures in the case of the chloride. Potential barriers to rotation have been calculated and compared with NMR activation energies to gain insight into the relationship between the two kinds of result. The external barrier for NH 3 + reorientation and the internal barrier for N 2 H 6 2+ have been found to be 3597 and 709 cm −1 respectively for the chloride at 73 K, and 3066 and 676 cm −1 respectively for the bromide at 92 K. The chloride results clearly show that the barriers are slightly temperature dependent. It is concluded that the NMR activation energy for NH 3 + reorientation must also have a temperature dependence which is probably of the form E a = E a ′ ‐ CT . The discrepancies between the two types of results have been tentatively interpreted in terms of small sixfold contributions to the barriers.