H3+ recombination and bistability in the interstellar medium

H-3(+) has recently been detected using infrared absorption towards several dense clouds. We have already shown that models of interstellar chemistry can exhibit several stable steady states, due to the nonlinear behaviour of chemical equations in which H-3(+) plays a major role. We investigate that influence of various astrophysical parameters that control the evolution and the final state of the gas, such as the density, the cosmic-ray ionization rate, the elemental depletions, and the H-3(+) dissociative recombination rate (which is a key reaction). We show that these parameters lead to bistability for a range of physical conditions appropriate to interstellar clouds and discuss more specifically their influence on the H-3(+) abundance in dark clouds. Both steady-state and evolutionary aspects are discussed.