  A theoretical rate constant for the associative detachment reaction
Rb($^{2}S$)$+$OH$^{-}$($^{1}\Sigma^{+}$)$\rightarrow \,$
RbOH($^{1}\Sigma^{+}$)$+\,e^{-}$ of 4$\,\times$10$^{-10}$cm$^{3}$s$^{-1}$ at
300 K has been calculated. This result agrees with the experimental rate
constant of 2$^{+2}_{-1}\,\times10^{-10}$cm$^{3}$s$^{-1}$ obtained by Deiglmayr
\textit{et al.} (Phys. Rev. A 86, 2012) for a temperature between 200 K and 600
K. A Langevin-based dynamics which depends on the crossing point between the
anion (RbOH$^{-}$) and neutral (RbOH) potential energy surfaces has been used.
The calculation were performed using the ECP28MDF effective core potential to
describe the rubidium atom at the CCSD(T) level of theory and extended basis
sets. The effect of ECPs and basis set on the height of the crossing point, and
hence the rate constant, has been investigated. The temperature dependence of
the latter is also discussed. Preliminary work on the potential energy surface
for the excited reaction channel Rb($^{2}P$)+OH$^{-}$($^{1}\Sigma^{+}$)
calculated at the CASSF-icMRCI level of theory is shown. We qualitatively
discuss the charge transfer and associative detachment reactions arising from
this excited entrance channel.
