Kinetics of the thermal back relaxation time of the photoinduced nematic-isotropic transition

We report on the temperature dependence of the response time for the photochemical and thermal back relaxation processes observed in a material exhibiting a photostimulated, isothermal nematic-isotropic phase transition. It is found that the time required for the system to achieve the photostationary state as well as to recover the original state after photoirradiation with a uv beam is a smooth function of the absolute temperature of the sample, except in the vicinity of the transition. The duration of the recovery can be split into two parts: delay time and response time. Using a simple description based on the Maier-Saupe model, we show that the temperature dependence of the response time can be understood in terms of the order parameter excess between the equilibrium and photostimulated states.