K. Acharyya2 and Sandip K.
Chakrabarti2,1,
1
Centre for Space Physics, Chalantika 43, Garia Station Rd., Kolkata,
700084, India
2
S. N. Bose National Centre for Basic Sciences, Salt Lake, Kolkata
700098, India
Abstract. We study the efficiency of molecular hydrogen
recombination on
grain surfaces using both the rate equation (which tracks the average
number
of species) and the master equation (which tracks the expectation values
of
the species). We have incorporated Langmuir-Hinselwood rejection term in
obtaining the efficiency. We use this result to compute H2 production
rates as
a function of the grain temperature and accretion rate of atomic
hydrogen. Our
general conclusion is that the H2 formation efficiency is very much
dependent
on the grain temperature and the accretion rate of the atomic hydrogen
on
grains. We provide tables of H2 production rates which could be readily
used
for future calculation of production of more complex molecules in the
gas phase.
Keywords :Molecular cloud - star formation - grain chemistry
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