  Inelastic collisions and elementary chemical reactions proceeding through the
formation and subsequent decay of an intermediate collision complex, with an
associated deep well on the potential energy surface, pose a challenge for
accurate fully quantum mechanical approaches, such as the close-coupling
method. In this study, we report on the theoretical prediction of
temperature-dependent state-to-state rate coefficients for these complex-mode
processes, using a statistical quantum method. This statistical adiabatic
channel model is benchmarked by a direct comparison using accurate rate
coefficients from the literature for a number of systems (H2 + H+, HD + H+, SH+
+ H, and CH+ + H) of interest in astrochemistry and astrophysics. For all of
the systems considered, an error of less than factor 2 was found, at least for
the dominant transitions and at low temperatures, which is sufficiently
accurate for applications in the above mentioned disciplines.
