The fluorescence from a thin ruby film, formed by epitaxial growth on a sapphire substrate, is shown to be a sensitive monitor of both the irradiation dose and the strain produced by irradiation of argon ions having an end of range exceeding the thickness of the ruby film. Decreases in fluorescence intensity are detectable for doses in excess of 1012cm2, whereas no damage is detectable by Rutherford backscattering spectrometry/channeling until doses almost two orders of magnitude larger. Using the systematic shift in fluorescence frequency observed with irradiation, it is concluded that lattice strain accumulates rapidly for doses in excess of 1014cm2. ©1996 American Institute of Physics.