SIMBAD references

HCN is a molecule central to interstellar chemistry, since it is the simplest molecule containing a carbon-nitrogen bond and its solid state chemistry is rich. The aim of this work was to study the NH3 + HCN ⟶ NH+4CN- thermal reaction in interstellar ice analogues. Laboratory experiments based on Fourier transform infrared spectroscopy and mass spectrometry were performed to characterize the NH+4CN- reaction product and its formation kinetics. This reaction is purely thermal and can occur at low temperatures in interstellar ices without requiring non-thermal processing by photons, electrons or cosmic rays. The reaction rate constant has a temperature dependence of k(T) = 0.016+ 0.010- 0.006 s^-1exp(-2.7±0.4 kJ mol^-1/RT) when NH3 is much more abundant than HCN. When both reactants are diluted in water ice, the reaction is slowed down. We have estimated the CN- ion band strength to be A_CN^- = 1.8±1.5x10-17cm molecule-1 at both 20 and 140 K. NH+4CN- exhibits zeroth-order multilayer desorption kinetics with a rate of k_des(T) = 1028 moleculecm-2 s^-1exp(-38.0±1.4 kJ mol^-1/RT). The NH3 + HCN ⟶ NH+4CN- thermal reaction is of primary importance because (i) it decreases the amount of HCN available to be hydrogenated into CH2NH, (ii) the NH+4 and CN- ions react with species such as H2CO and CH2NH to form complex molecules and (iii) NH+4CN- is a reservoir of NH3 and HCN, which can be made available to a high-temperature chemistry.