Flash photolysis

Flash photolysis is a pump-probe laboratory technique, in which a sample is firstly excited by a strong pulse (called pump pulse) of light from a laser of nanosecond, picosecond, or femtosecond pulse width or by a short-pulse light source such as a flash lamp. This first strong pulse starts a chemical reaction or leads to an increased population for energy levels other than the ground state within a sample of atoms or molecules. Typically the absorption of light by the sample is recorded within short time intervals (by a so-called test pulses) to monitor relaxation or reaction processes initiated by the pump pulse.