  A detailed quantum analysis of a ionic reaction with a crucial role in the
ISM is carried out to generate ab initio reactive cross sections with a quantum
method. From them we obtain the corresponding CH+ depletion rates over a broad
range of temperatures. The new rates are further linked to a complex chemical
network that shows the evolution in time of the CH+ abundance in
photodissociation region (PDR) and molecular cloud (MC) environments.
  The evolutionary abundances of CH+ are given by numerical solutions of a
large set of coupled, first-order kinetics equations by employing the new
chemical package KROME. The differences found between all existing calculations
from low-T experiments are explained via a simple numerical model that links
the low-T cross section reductions to collinear approaches where nonadiabatic
crossings dominate. The analysis of evolutionary abundance of CH+ reveals that
the important region for the depletion reaction of this study is that above 100
K, hence showing that, at least for this reaction, the differences with the
existing low-temperature experiments are of essentially no importance within
the astrochemical environments. A detailed analysis of the chemical network
involving CH+ also shows that a slight decrease in the initial oxygen abundance
might lead to higher CH+ abundance since the main chemical carbon ion depletion
channel is reduced in efficiency. This simplified observation might provide an
alternative starting point to understand the problem of astrochemical models in
matching the observed CH+ abundances.
