IR spectra obtained after ion bombardment of (a) C₂H₂:H₂O and (b) C₂H₂:H₂¹⁸O mixed ices by 200 keV H⁺ at 17 K. The applied deposition ratios were 0.4:1 and 0.2:1 for C₂H₂:H₂O and C₂ H₂:H₂¹⁸O mixed ices, respectively. The applied H⁺ fluence for each experiment is 6.0 × 10¹⁴ protons cm⁻² (~ 16.4 eV 16u-molecule⁻¹). The blue arrows indicate features that are shifted because of ¹⁸O and the dashed lines reflect the absorption features of COMs with ¹⁶O. IR spectra are offset for clarity.