Selection of spectra of C/2023 H2 obtained with CRIRES⁺. The top panel shows the identification of many lines of CO in the M3418 setting (all the detectors, order 12). In the middle plots, we show from left to right emission lines of CH₄ (setting L3302, detectors 1 and 2, order 17) and C₂H₆ (setting L3377, detector 1, order 17); other species such as methanol and OH are barely visible. In the bottom panel, we show detection of water and OH, in setting L3302, detectors 1 and 2, and order 19. For each panel, the modelled spectra is shown in red; single models are shifted from the observed spectra and colour-coded (CO: orchid, H₂O: green, C₂H₆: dark magenta, CH₄: dark cyan, CH₃OH: chocolate, OH (prompt emission): olive). Below the models, we plotted in grey the residual (after subtraction of the modelled emissions) together with the expected stochastic noise envelope (±1σ) in yellow.