Determination of the absorption profile σ_2ars for the two cases of 2ARS contribution (red curve in both figures). In both figures, the blue curve is the normalized absorption cross section of naphthalene σ_naph (Grosch et al. 2015). The blue dotted line is a linear extrapolation of the naphthalene cross section for a large wave number. In both figures, the red and blue areas are the total absorption of the 2ARS profile 𝒜_2ars and of the S₃ ← S₀ transition of naphthalene 𝒜_naph, respectively. These areas are defined to be equal. In panel (a), the black curve is the interstellar bump parametrization from Fitzpatrick & Massa (2007) (see equation 3). In panel (b), the black curve is the mean REMPI spectrum 〈S_m〉 defined in equation 5. Also in panel (b), the yellow dashed line is a Gaussian function A exp that has been fitted to 〈S_m〉. The fitting parameters are shown in Table B.1 (fitting was done using the least squares method).