NEUTRON COMPTON-SCATTERING STUDY OF PROTON-TRANSFER DYNAMICS IN PARTIALLY DEUTERATED N-METHYLACETAMIDE - CD3CONHCD3

Neutron Compton scattering measurements for the partially deuterated N -methylacetamide molecule (CD3CONHCD3) at 4.5 K give the powder averag ed mean frequency of the proton modes: 1457 +/- 38 cm(-1). This value is lower than that anticipated from the assignment scheme based on inf rared and Raman spectra (approximate to 1790 cm(-1)). Anharmonicity an d vibrational coupling are such that that assignment scheme must be re jected. The mean frequency obtained with the assignment based on inela stic neutron scattering (INS) (approximate to 1230 cm(-1)) appears rea listic. These conclusions are in accord with force-field calculations in the impulse approximation.