Depolarized scattering at a binary liquid critical point

Abstract
Interferometric and diffraction grating measurements of the depolarized light scattering linewidths in the critical region of a nitroethane‐3 methylpentane liquid mixture reveal a relatively weak dependence of the orientational linewidth on ΔT. Plots of the log of the orientational relaxation time vs log ΔT, logτ=−r logΔT+C, yield r=0.031±0.008 while plots of logτ=r′/T+C′ yield r′=1090±292 K. The wide background in the depolarized spectrum exhibits a HWHM of 30 cm−1 which does not change as the critical point is approached. In addition, the HWHM of the completely polarized 875 cm−1 Raman band of nitroethane was found to be 2.1 cm−1 and also to be insensitive to temperature.