A new method to investigate atmospheric chemical kinetics is presented. It is based on the pump and probe principle. Preliminary measurements are described on the decay rate of OH in the planetary boundary layer its concentration has been raised by laser flash photolysis of background ozone and subsequent reaction of the O(1D) with atmospheric water vapor. The measured OH disappearance kinetics are compared with model calculations yielding information on the fast reaction of OH. The presented point measurements can be extended to a range resolved differential absorption LIDAR technique.