Torsional and librational modes of the monomethylammonium ion, CH3NH +3, in its salts, studied by inelastic neutron scattering
Abstract
This paper reports the direct observation, assignment and study of the torsional and librational vibrations of the ions CH3NH+3, CD3NH+3 and CH3ND+3 in the various phases of their salts with Cl–, Br–, I– and PF–6, by inelastic neutron scattering (I.N.S.). From these observations it is possible to derive a value for the torsional frequency of the “free” CH3NH+3 ion, which is intermediate between that of C2H6 and N2H2+6. It is also possible to calculate the internal and external barriers to rotation of the ion in certain of the lattices.