The resonance fluorescence of atomic oxygen, nitrogen, krypton, and argon was measured in the vacuum-uv region as a function of the atom concentration. In a model the calculated fluorescence intensity is approximated to the experimental dependences by variation of a single parameter k0 . The best fit to the experimental data defines k0 as effective absorption coefficient in the central part of the resonance lines. The application of the resonance fluorescence as an analytical tool for atom reactions at low pressures is discussed.