Complex dynamics and the stimulated gain spectrum of pentylcyanobiphenyl in the isotropic phase

We have measured high resolution polarized and depolarized stimulated gain spectra of the liquid crystal pentylcyanobiphenyl (5CB) in its isotropic phase between 36.2 and 122°C. Spectral features associated with slow collective reorientation, acoustic waves (Brillouin peaks), and rapid anisotropy fluctuations are all present and can be simultaneously measured with high resolution in a single spectrum. Our results for both the slow and intermediate timescale reoirientational dynamics are in good agreement with recent transient-grating optical Kerr effect measurements on 5CB.