A new technique to determine the relative spatial distribution of radical concentration without Abel transformation is presented. By monitoring spatial light intensities with an optical probe inserted into the plasma, the relative spatial distribution of the radical species is investigated. The relative spatial uniformity of the radical atom is also investigated by normalizing the emission intensity of the radical atoms to the plasma parameters (electron-impact excitation rate coefficient and plasma density). The movable probe technique has a simple configuration and provides accurate information on the relative spatial distribution of radicals in any plasma source. (C) 1995 American institute of Physics.