Thermal and chemical relaxations near the critical point of chlorine.

Abstract

Relaxation times in chlorine near its liquid-vapor critical point have been studied after thermal and chemical perturbations. The chemical perturbation was by photolysis with ultraviolet light, to dissociate the chlorine molecules. The chemical relaxation was very fast, contrary to earlier reports. The relaxation after a thermal perturbation was very slow (${10}^{3}$ s). The thermal relaxation time near the critical point behaved as \ensuremath{\tau}=${\mathrm{Ct}}^{\mathrm{\ensuremath{-}}0.94\ifmmode\pm\else\textpm\fi{}0.10}$ [where t\ensuremath{\equiv}(T-${T}_{c}$)/${T}_{c}$ and ${T}_{c}$ is the transition temperature], in contrast to the expectation that \ensuremath{\tau} would be determined by the thermal diffusivity and have a critical exponent (-0.63).