Frequency stabilization of tunable infrared diode lasers for time-resolved monitoring of transient species

Stabilization of an infrared diode laser on the absorption line of a transient species has been developed in a laser flash photolysis/infrared diode laser absorption experiment used for kinetic studies. The stabilization is achieved by modulating the optical pathlength of a confocal Fabry-Perot interferometer instead of the injection current of the laser. It is therefore of prime interest for studies in chemical kinetics or photochemistry, where signals are acquired at fixed frequency and where the timescale of the reactions prohibits modulation of the signal. This method is demonstrated on the detection of HCO radical following 266-nm laser photolysis of acetaldehyde.