Ion chemistry in the early universe: revisiting the role of HeH+ with
  new quantum calculations
  The role of HeH+ has been newly assessed with the aid of newly calculated
rates which use entirely ab initio methods, thereby allowing us to compute more
accurately the relevant abundances within the global chemical network of the
early universe. A comparison with the similar role of the ionic molecule LiH+
is also presented. Quantum calculations have been carried out for the gas-phase
reaction of HeH+ with H atoms with our new in-house code, based on the negative
imaginary potential method. Integral cross sections and reactive rate
coefficients obtained under the general conditions of early universe chemistry
are presented and discussed. With the new reaction rate, the abundance of HeH+
in the early universe is more than one order of magnitude larger than in
previous studies. Our more accurate findings further buttress the possibility
to detect cosmological signatures of HeH+.
