The charge recombination rate in DNA hairpins is investigated. The distance dependence for the charge recombination rate between stilbene donor (Sd
) and stilbene acceptor (Sa
) linkers separated by an AT bridge has a double exponential form. We suggest that this dependence is associated with two tunneling channels distinguished by the presence or absence of the Cl
counterion bound to Sd
. Experiment-based estimates of counterion binding parameters agree within reasonable expectations. A control experiment replacing the Cl
ion with other halide ions is suggested. Counterion substitution allows modification of the charge recombination rate in either direction by orders of magnitude.