Calculated sputtering rate versus ionisation rate from Eq. (7) using the prescription presented in this work for perylene (C₂₀H₁₂, in red) and coronene (C₂₄H₁₂, in yellow). The filled region delimited by dashed lines shows the expected range of variations based on the uncertainties in the measurements. The upper x-axis gives the approximate visual extinction in a dense cloud corresponding to the ionisation rate of the lower x-axis, assuming an ionisation rate of 3 × 10⁻¹⁶ s⁻¹ outside the cloud and based on observed cosmic-ray ionization rate attenuation with the visual extinction (e.g. Wakelam et al. 2021; Neufeld & Wolfire 2017; Indriolo & McCall 2012).