The O(P-3) atom produced in the 193 nm photolysis of N2O has been detected by a technique of vacuum-ultraviolet laser-induced fluorescence spectroscopy around 130 nm. The quantum yield value of the O((3)p) atoms produced directly in the photolysis of N2O at 193 nm at room temperature has been determined to be 0.005 +/- 0.002. The O(P-3) atom formation process in the reaction of O(D-1) + N2O is also studied, and the channel branching ratio of O(P-3) + N2O has been determined to be 0.04 +/- 0.02 among the product channels, 2NO, N-2 + O-2, and O(P-3) + N2O. Photodissociation processes of N2O at 193 nm and reaction processes of O(D-1) + N2O system have been discussed on the basis of the experimental results. Because of importance of the O(D-1) + N2O reaction in the stratosphere, impact of the experimental result of 0(3p) formation from the O(D-1) + N2O reaction on the stratospheric chemistry is also studied by one-dimensional atmospheric model calculations.