Comparison of observed (dots) and synthetic spectra for FU Mon (SC-type). The continuous line represents the synthetic spectrum calculated with a ¹⁶O/¹⁸O ratio of 400. Dashed lines represent synthetic spectra computed without ¹⁸O and with ¹⁶O/¹⁸O of 200, respectively. The position of some ¹²C¹⁸O blends are marked with vertical lines. Note that some spectral features are not well reproduced by the synthetic spectra.