For example, it is possible that N2O adsorption can occur at isolated -C * sites, whereas O2 dissociative adsorption requires two adjacent -C * sites to bind the two O atoms. Sublimation of graphite involves desorption of small Cn clusters, with C3 and C1 dominating, and while it is unclear what type of surface sites the clusters desorb from or leave behind, it is certainly possible that sublimation tends to remove sites with adjacent -C * centers, that would suppress O2 adsorption sites.