Low frequency Raman and quasi-elastic scattering from para-azoyanisole (PAA) has been investigated between 5 and 100 cm-1, near the crystal to nematic phase transition at 117°C. A central quasi-elastic wing, qualitatively shown to be associated with a Debye-like process is observed at 114°C and above. The intensity of the Raman lines determined from a computer fit of the lattice mode Raman spectra to lorentzian expressions show a relatively sharp decrease in the vicinity of Tc, indicative of a first order transition. No indication of a propagating soft mode near Tc was found. Raman peaks at 13, 34, 54 ± cm-1 superimposed on the strong quasi-elastic scattering were observed in the nematic liquid crystal phase.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry