Radiolysis of ammonia-containing ices by heavy cosmic rays inside dense molecular clouds

Abstract

We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV ⁵⁸Ni¹³⁺) with interstellar ammonia-containing (H₂O:NH₃:CO) ice analog in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed at the heavy ion accelerator GANIL in Caen, France. In-situ analysis have been performed by a Fourier transform infrared spectrometer. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide are determined and the estimated half life for the studied species inside dense molecular clouds is 2-3 × 10⁶ years. The IR spectra of organic residue produced by the radiolysis have revealed, at room temperature, five bands that are tentatively assigned to vibration modes of the zwitterionic glycine (NH₃⁺CH₂COO⁻).