Nitrogen, oxygen, and carbon atoms have been detected by optical emission spectroscopy in a common flowing post-discharge of an Ar-x CH4 rf plasma torch and an Ar-2%N-2 microwave discharge. Gas temperature as determined from CN and N-2 rotational systems is 3200+/-200 K in the rf torch and 700+/-100 K in the post-discharge at a time 3 x 10(-2) s after the rf plasma torch. From the intensities of the N-2 1st positive system, of NO, and of CN violet bands, the atom densities have been determined as 2 x 10(16) cm(-3) for N, 10(15) cm(-3) for O, and 6 x 10(12) cm(-3) for C in the post-discharge at p = 650 torr, with 10(-3) of CH4 in rite Ar torch.