Dynamic frequency stabilization of diode lasers has been developed and used in a laser flash photolysis/infrared diode laser absorption technique. The dynamic frequency stabilization is achieved by modulating the operating current of the diode laser and using a lock-in amplifier to lock the frequency to the centre of the absorption line. This technique also has the ability to switch off the modulation using an optically coupled FET during data collection. Employment of a Herriott-type multipass reflection cell allows for efficient overlapping of photolysis and probe beams and increases the detection sensitivity. Study of the Cl + C2H6 reaction has shown that the newly developed system is sensitive and reliable.