Molecular Hydrogen Formation on Astrophysically Relevant Surfaces
N. Katz, I. Furman, O. Biham, V. Pirronello, G. Vidali;
ApJ, 1999, 522, 305
ABSTRACT:Recent experimental results about the formation of molecular hydrogen on astrophysically relevant surfaces under conditions close to those
encountered in the interstellar medium are analyzed using rate equations.
The
parameters of the rate equation model are fitted to temperature-programmed
desorption curves obtained in the laboratory.
These parameters are the
activation energy barriers for atomic hydrogen diffusion and desorption, the
barrier for molecular hydrogen desorption, and the probability of
spontaneous desorption of a hydrogen molecule upon recombination.
The model is a
generalization of the Polanyi-Wigner equation and provides a description of both
first- and second-order kinetic processes within a single model.
Using the
values of the parameters that best fit the experimental results, the
efficiency of hydrogen recombination on olivine and amorphous carbon surfaces is
obtained for a range of hydrogen flux and surface temperature pertinent to a wide
range of interstellar conditions.
KEYWORDS: ism: dust, extinction, ism: abundances, ism: molecules, molecular processes
CODE: katz99