Study of proton transfer processes in solution using the laser induced pH-jump: A new experimental setup and an improved data analysis based on genetic algorithms

We present an experimental setup for studying proton transfer reactions in solution and an innovative data analysis based on a genetic algorithm. We have used o-nitrobenzaldehyde to irreversibly release protons in an aqueous solution upon photolysis with an intense UV nanosecond laser pulse. Reactions of the photodetached protons with pH indicators have been followed by monitoring the changes in absorbance at 632.8 nm with a He-Ne laser and a Si avalanche photodiode. The setup has laser-limited time resolution and single shot sensitivity. The pH jump established with the laser shot lasts similar to 30 ms, during which proton transfer reactions can be followed. The proposed methodology represents a simplification in the kinetic schemes with respect to the previous protocols based on the use of reversible caged protons. (C) 1998 American Institute of Physics.