C-type shock modelling -- the effect of new H$_2$-H collisional rate
  coefficients
  We consider collisional excitation of H$_2$ molecules in C-type shocks
propagating in dense molecular clouds. New data on collisional rate
coefficients for (de-)excitation of H$_2$ molecule in collisions with H atoms
and new H$_2$ dissociation rates are used. The new H$_2$-H collisional data are
state of the art and are based on the most accurate H$_3$ potential energy
surface. We re-examine the excitation of rotational levels of H$_2$ molecule,
the para-to-ortho-H$_2$ conversion, and H$_2$ dissociation by H$_2$-H
collisions. At cosmic ray ionization rates $\zeta \geq 10^{-16}$ s$^{-1}$ and
at moderate shock speeds, the H/H$_2$ ratio at the shock front is mainly
determined by the cosmic ray ionization rate. The H$_2$-H collisions play the
main role in the para-to-ortho-H$_2$ conversion and, at $\zeta \geq 10^{-15}$
s$^{-1}$, in the excitation of vibrationally excited states of H$_2$ molecule
in the shock. The H$_2$ ortho-to-para ratio (OPR) of the shocked gas and column
densities of rotational levels of vibrationally excited states of H$_2$ are
found to depend strongly on the cosmic ray ionization rate. We discuss the
applicability of the presented results to interpretation of observations of
H$_2$ emission in supernova remnants.
