The formation of H$_2$ on interstellar dust
W. W. Duley, D. A. Williams;
MNRAS, 1993, 260, 37
ABSTRACT:We consider the process of H2 formation on realistic dust grain materials.
We argue that formation on amorphous H2O ice and polymeric cabonaceous
materials leaves H2 in a highly excited vibrational state, while formation on
aromatic carbonaceous material gives H2 in states of low excitation.
We
calculate the H2 vibrational emission intensity arising from H2 formation in
dark clouds from which UV radiation is excluded.
We show that this emission
may be detectable with present technology, and should certainly be
detectable at very high spectral resolution.
Formation of H2 on amorphous ice
leads to local heating which may desorb local CO.
We propose that the
observed extinction threshold for solid CO is controlled by this process, and
show that it leads to CO deposition in distinct polar and non-polar
environments, as observed.
Observational consequences of this prediction are
described.
KEYWORDS: cosmic dust, hydrogen, interstellar matter, molecular clouds, dark matter, emission spectra, ice, molecular excitation, vibrational spectra
CODE: duley93