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 averaged mean frequency of the photon modes: 1457 ± 38 cm−1. This value is lower than that anticipated from the assignment scheme based on infrared and Raman spectra (⋍1790 cm−1). Anharmonicity and vibrational coupling are such that that assignment scheme must be rejected. The mean frequency obtained with the assignment based on inelastic neutron scattering (INS) (⋍1230 cm−1) appears realistic. These conclusions are in accord with force-field calculations in the impulse approximation.