from first principles PP-I-1

PP-I-7On the Role of Energy Distribution Functions of the Ad-Atoms inRecombinative Adsorption at Catalytic SurfacesMolinari E., Tomellini M.Dipartimento di Scienze e Tecnologie Chimiche Università di Rome Tor Vergata, Via dellaRicerca Scientifica 00133 Roma, Italytomellini@uniroma2.itWe present a brief review on the modeling of the vibrational distribution functions of theadspecies in diatom formation at catalytic surfaces. The kinetic approach, which deals with areactive mobile adlayer of adatoms under steady state conditions, is based on the use ofmaster equations which describe the main processes occurring during the adsorptionrecombinationevents [1,2]. They are, the accommodation of the adsorbed species via energydissipation in the adsorption potential well and the formation of the diatom. In particular, wefocus our attention on the impact of the distribution function on reaction rate and, in turn, onthe interplay between reaction rate and energy disposal to the solid and to the adlayer. Thekinetic model makes it possible to determine the conditions under which non-equilibriumenergy distribution functions characterize the vibrational state of the adlayer. In fact, it isshown that “hyper-thermal” energy distribution functions entails a multi-level “hot-atom”reaction mechanism. Furthermore, the transition from thermal to hyper-thermal reaction ratehas been studied as a function of rate coefficients, and the vibrational temperature of the “hotatoms”estimated.[1] M. Tomellini, React. Kinet. Catal. Lett. 97 (2009) 179[2] E. Molinari, M. Tomellini, Z. Phys. Chem. 224 (2010) 743123