  We present a quantum-mechanical study of the exothermic 7LiH reaction with H.
Accurate reactive probabilities and rate coefficients are obtained by solving
the Schrodinger equation for the motion of the three nuclei on a single
Born-Oppenheimer potential energy surface (PES) and using a coupled-channel
hyperspherical coordinate method. Our new rates indeed confirm earlier,
qualitative predictions and some previous theoretical calculations, as
discussed in the main text. In the astrophysical domain we find that the
depletion process largely dominates for redshift (z) between 400 and 100, a
range significant for early Universe models. This new result from
first-principle calculations leads us to definitively surmise that LiH should
be already destroyed when the survival processes become important. Because of
this very rapid depletion reaction, the fractional abundance of LiH is found to
be drastically reduced, so that it should be very difficult to manage to
observe it as an imprinted species in the cosmic background radiation (CBR).
The present findings appear to settle the question of LiH observability in the
early Universe. We further report several state-to-state computed reaction
rates in the same range of temperatures of interest for the present problem.
