ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O O O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation O O B-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: to bounce against the surface to gain velocity in the direction perpendicular to the surface. The simplest way to treat this process is to assume an elastic collision, Here is the fraction of kinetic energy retained by the product colliding with the surface, which has an effective mass . For the specific case of hyperthermal scattering of O on graphite surface, Hayes et al. (2012) have proposed an equivalent mass of 130 a.m.u. The effective mass is much higher than one single C atom or even a carbon ring because the rigidity of the surface induces a collective behavior of the atom and a higher effective mass. The chemical energy is certainly split in many different ro-vibronic states, not at all in thermal equilibrium. We assumed that an equal share of energy is spread throughout all the degrees of freedom, so that the total chemical energy available for the kinetic energy perpendicular to the surface is . We assumed that the only velocity perpendicular to the surface corresponds to a distribution of speed and temperature. In this sense, . The probability for the product to have an energy (or liberation velocity) higher than the binding energy becomes In Fig. 3 we compare the results obtained experimentally (blue triangles) to our predictions. We first used a constant of 0.4, which implies that we assumed that 40% of the total energy is retained by the product (red hexagons). In this case, our predictions do not reproduce the experimental results well. In a second step, we considered a fraction that depends on the mass of the products, as described in Eq. (1). These predictions are represented as green squares and do match the chemical desorption efficiencies observed experimentally very well. This clearly indicates that the chemical desorption process is sensitive to the binding energy, the energy distributed in the products (depending on their mass), and the degrees of freedom. For some of the reactions such as OH+H, O+H, our predictions slightly underestimate the experimental results. Table 2 Binding energies on bare and icy surfaces. Notes. For HCO, CHO, and CHOH we assume . (a) Cazaux Tielens (2004) ; (b) Bergeron et al. (2008) ; (c) Al-Halabi van Dishoeck (2007) , Amiaud et al. (2007) ; (d) Pirronello et al. (1997) ; (e) Amiaud et al. (2006) for low coverage; (f) Minissale et al. (2015) ; (g) Dulieu et al. (2013) ; (h) Speedy et al. (1996) , Fraser et al. (2001) energy derived of 5800 K with pre-factor of 10 s here corrected to have a pre-factor of 10 s; (i) Noble et al. (2012a) ; (j) Borget et al. (2001) , Minissale (2014) ; (k) Karssemeijer Cuppen (2014) ; (l) Garrod Herbst (2006) ; (m) Noble et al. (2012b) ; (n) Collings et al. (2004) ; (o) Fuchs et al. (2006) ; (p) extrapolated from Kimmel et al. (2001) . The formula (Eq. (2)) can be translated to the case of silicates surfaces. The efficiency is slightly lower, and thus reducing the effective mass from 130 to 110 matches the most constrained reaction (O+O) very well. Taking the