Temperature dependence of the vibrational spectra of acetanilide: Davydov solitons or Fermi coupling?

✍ Scribed by Clifford T. Johnston; Basil I. Swanson

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 570 KB
• Volume: 114
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(85)85139-3

✦ Synopsis

The unusual temperature dependence of the amide-i region in the IR spectrum of acetamlide (C6HsNHCOCH3) has recently been attirbuted to a self-trapped Davydov-hke sohton. The temperature dependence of the smgle-crystal Raman scattermg, from acetan&de and its N-D and '%-0 substrtuted analogs III the phonon and internal mode regions has now been studled. The behanor of the armde-I regon m the Eaman spectra of the normal lsotoplc spccres IS similar to that observed carher In mtiared studres. However, on the basis of results obtamed from the N-D and 13C-0 substituted species the unusual temperature dependence rn the 1650 cm-' region has been attnbutcd to Ferrru wuphng of the amide-1 fundamental and a combmation band mvoivmg the in-plane N-H deformation and a low-frequency torsional mode. As temperature is lowered, the strong blue&uft of the torsional mode results UI a commensurate blue-stit in the combmatior. level thereby mcre=asmg the Fernu coupling. Temperature tunmg of the Fermi couphng results in the anomalous htemty chages observed in the IR and Raman spectra of the anude-i region for the normal isotopic species.