The O( 3 P) atom produced in the 193 nm photolysis of N 2 O has been detected by a technique of vacuumultraviolet laser-induced fluorescence spectroscopy around 130 nm. The quantum yield value of the O( 3 P) atoms produced directly in the photolysis of N 2 O at 193 nm at room temperature has been determined to be 0.005 ( 0.002. The O( 3 P) atom formation process in the reaction of O( 1 D) + N 2 O is also studied, and the channel branching ratio of O( 3 P) + N 2 O has been determined to be 0.04 ( 0.02 among the product channels, 2NO, N 2 + O 2 , and O( 3 P) + N 2 O. Photodissociation processes of N 2 O at 193 nm and reaction processes of O( 1 D) + N 2 O system have been discussed on the basis of the experimental results. Because of importance of the O( 1 D) + N 2 O reaction in the stratosphere, impact of the experimental result of O( 3 P) formation from the O( 1 D) + N 2 O reaction on the stratospheric chemistry is also studied by one-dimensional atmospheric model calculations.