Dynamics of rare gas desorption from Pt(111) induced by collisions with photogenerated hot oxygen atoms

We present a classical trajectory study of the collision-induced desorption of rare gas (Rg=Ar, Xe) atoms from Pt(111) by ‘hot’ O atoms generated by photodissociating coadsorbed O2. Empirical potential energy functions are used to describe the Rg/O/Pt(111) systems. The calculated angular and translational energy distributions of the desorbed Ar and Xe are in good agreement with experimental observations. It is found that the desorption dynamics involves two collisions. The first collision between O and Rg supplies the necessary kinetic energy for desorption, whereas the second collision between the departing Rg atom and a coadsorbed Rg atom results in a desorption angle of 25–35° from the surface normal for Ar and 35–45° for Xe. The light oxygen atom is found to chatter between the Xe atom and the surface during an O–Xe collision, enhancing the energy transfer.