Probability of desorption of a given cluster size from a dust grain at temperature T = 200 K (grey lines) and T = 400 K (coloured lines) after absorption of an X-ray for the four considered PAH species between 24 C atoms and 54 C atoms. The different shades of colour indicate the assumed excitation energy (light: 15 eV, medium: 25 eV, dark: 35 eV). The considered PAH species has a much larger effect on the desorption probability than the PAH cluster size or dust grain temperature.