  We present a theoretical description of dissociative recombination of
triatomic molecular ions having large permanent dipole moments. The study has
been partly motivated by a discrepancy between experimental and theoretical
cross-sections for dissociative recombination of the HCO$^+$ ion. The HCO$^{+}$
ion has a considerable permanent dipole moment ($D\approx$4 debye), which has
not been taken explicitly into account in previous theoretical studies. In the
present study, we include explicitly the effect of the permanent electric
dipole on the dynamics of the incident electron using the generalized quantum
defect theory, and we present the resulting cross section obtained. This is the
first application of generalized quantum defect theory to the dissociative
recombination of molecular ions.
