FTIR spectra of a coronene:water:argon matrix in the spectral ranges 3800–2900 cm^-1 (top panel) and 1350–1100 cm^-1 (lower panel). The spectra are (a) codeposited coronene:water:argon matrix at 10 K; (b) the same matrix after three minutes of irradiation with a mercury lamp; (c) the difference spectrum (b)–(a), multiplied by ten. The attributions of water, coronene, and photoproducts are presented in Table 1, and the bands attributed to water and photoproducts are highlighted.