Ambient field adopted in the modelling. The near-IR (2.9–4 μm) region was directly obtained from NIRSpec observations in this work (see Fig.B.1). The mid-IR part (5.5-15 μm) is a Spitzer spectrum, measured around the disc HD97300, whose flux was scaled to mimick the expected ISRF flux in the 7.7 μm JWST broadband filter. In the mid-IR, the contribution to an underlying continuum from the emission of very small grains (e.g. Compiègne et al. 2011) would be required to derive a more accurate ambient field emission profile.