Three contour plots showing the TPD traces for toluene exposed to different fluences of H atoms. (a) Pristine toluene (92 amu) and its H-loss fragment (91 amu) observed at around 200 K. (b) TPD of a toluene monolayer exposed to a fluence of 8.6 × 10¹⁸ cm⁻² H atoms showing a reduction in the toluene related desorption features along with the appearance of new desorption products with masses 98 and 83 amu at lower temperatures, attributed to the formation of methyl-cyclohexane. (c) TPD corresponding to an H-atom fluence of 17.3 × 10¹⁸ cm⁻², where the hydrogenated species and the toluene now all desorb at lower temperatures.