Photodesorption rates from the literature reported as a function of enthalpy of sublimation. The variations in the absolute determination of the rate for various experiments are reported in Table 2. The right ordinate axis translates the rates into effective rates for a given ionisation rate ζ, assuming about 920 VUV photons cm⁻² s⁻¹ for an ionisation rate of ζ = 10⁻¹⁷ s⁻¹. See text for details.