SIMBAD references

Although deuterium isotope fractionation in cold, dark interstellar clouds is reasonably well understood via gas-phase chemistry, there are some discrepancies between observation and theory. For example, the observed abundance ratio between the deuterated species C₃HD and the cyclic molecule C₃H₂ is significantly higher than most theoretical values unless the exchange reaction C₃H₃⁺+ HD C₃H₂D⁺+H₂ is efficient. In this paper, we report quantum chemical and dynamical calculations on this reaction, which show it to possess a large activation energy barrier and to be very slow at all normal interstellar temperatures.