A SINGLE-SWEEP, NANOSECOND TIME RESOLUTION LASER TEMPERATURE-JUMP APPARATUS

We describe a fast temperature-jump (T-jump) apparatus capable of acqu iring kinetic relaxation transients via real-time fluorescence detecti on over a time interval from nanoseconds to milliseconds in a single s weep. The method is suitable for aqueous solutions, relying upon the d irect absorption of laser light by the bulk water. This obviates the n eed for additives (serving as optical or conductive heaters) that may interact with the sample under investigation. The longitudinal tempera ture profile is made uniform by counterpropagating heating pulses. Dea d time is limited to one period of the probe laser (16 ns). The appara tus response is tested with aqueous tryptophan and the diffusion-contr olled dimerization of proflavine. (C) 1996 American Institute of Physi cs.