Control of elementary chemical reactions by femtosecond light pulses

Essentially new approaches are proposed for controlling the yield of produc ts of a chemical reaction by femtosecond laser pulses. The main attention i s paid to the method based on the change in phase characteristics of femtos econd pulses. The quantum yield of the product NH(c(1)Pi) upon multiphoton photodissociation of ammonium in gas is shown to increase by a factor of tw elve with chirp variation from -1250 fs(2) to 2000 fs(2). It is demonstrate d by the example of two-proton transfer in [2,2'-bipyridyl],3,3'-diol in so lution that the approach based on the variation in phase characteristics of a pump femtosecond pulse can be also used for controlling reactions in sol utions.