Normalized intensity (around 0.5 and 3^′′ around the first peak) profiles across the front (cut #3 Abergel et al. 2024) averaged on 0.5^′′ perpendicular to the line cut. The illuminating star is on the right. (Top) Observed first rotational levels. (Bottom) Observed first rovibrational levels. Para rovibrational levels peaks behind ortho rovibrational levels and the pure rotational para line 0−0 S(2) peaks behind the ortho line 0−0 S(1).