LOW-FREQUENCY RAMAN-SPECTROSCOPY

Some intensity expressions for low-frequency Raman, far-IR and inelast ic neutron scattering are discussed. Low-frequency near infrared (NIR) -FT-Raman spectra (similar to 80 - 400 cm(-1)) of some proteins and th eir aqueous solutions are presented, along with low-frequency visible Raman spectra (10 - 400 cm(-1)) of their model systems, some liquid am ides. A low-frequency band is observed in the R(($) over bar v)-repres entation of these spectra at approximately 100 cm(-1) This band is ass igned to a mode involving atoms in hydrogen bonds. Three more quantita tive models are used to describe it. The first model describes these l ow-frequency bands in terms of longitudinal and transverse mode densit y of states curves of one-dimensional hydrogen-bonded chains, the seco nd model is a damped harmonic oscillator model, and the third model is the Gaussian cage model. A band with a maximum around 290 cm(-1) migh t be sensitive to the water structure in aqueous protein solutions.