A laser temperature jump apparatus based on commercial parts equipped with highly sensitive spectrophotometric detection

A temperature jump apparatus is described which is based mainly on commercially available components. Temperature jumps of about 2 degrees C in about 150 mu l of aqueous solutions can be produced within 10 mu s by absorption of the infrared radiation of a pulsed atomic iodine laser. The time range available for kinetic experiments is about 30 mu s to 1s. The necessary modifications of the commercial iodine laser are discussed. A prominent feature of the apparatus is the very high sensitivity of the spectrophotometric detection system in the visible spectral range. Signal-to-noise ratios of up to 2*10 4 are reached at a time resolution of 1 mu s. A method is described to determine the size of the temperature jump of each individual experiment. Thus not only the relaxation times, which are independent of the size of small temperature jumps, can be evaluated but also the corresponding relaxation amplitudes can be determined in a precise manner. Furthermore, an effective method to recycle the laser medium i-C 3 F 7 I is described.