Anomalous vibrational modes in acetanilide: a F.D.S. incoherent inelastic neutron scattering study
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The origin of the anomalous infra-red and Raman modes in acetanilide (C6H5NHCOCH3, or ACN)(1) , remains a subject of considerable controversy. One family of theoretical models involves Davydov-like solitons (2) nonlinear vibrational coupling (3), or “polaronic” localized modes (4)(5). An alternative interpretation of the extra-bands in terms of a Fermi resonance was proposed (6) and recently the existence of slightly non-degenerate hydrogen atom configurations (7) in the H-bond was suggested as an explanation for the anomalies.
In this paper we report some new results on the anomalous vibrational modes in ACN that were obtained by inelastic incoherent neutron scattering (INS) . Comparisons of the spectra of ACN and of five deuterated derivatives, greatly facilitates assignments of the main features.
KeywordsFermi Resonance Vibrational Coupling Methyl Mode Anomalous Mode Incoherent Neutron Scatter
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