Radiolysis of pyridine in solid water

We irradiated the complex organic molecule pyridine and mixtures of pyridine and water in the solid phase (thin icy films) at 12 K at different beam lines of the GANIL facility (ARIBE: 90 keV $$\hbox {O}^{\mathrm {6+}}$$ , SME: $$650\, \hbox {MeV Zn}^{\mathrm {26+}})$$ . The destruction of the initial molecule and the appearance of radiolytic products were followed by in-situ infrared absorption spectroscopy as a function of the projectile fluence with the CASIMIR experimental set-up of CIMAP. We measured the destruction cross section as a function of pyridine concentration. A clear dependence on the percentage of pyridine in $$\hbox {H}_{\mathrm {2}}\hbox {O}$$ was found: the destruction cross sections are significantly higher for small concentration, i.e. pure pyridine is more radioresistant than pyridine diluted in water ice at 12 K. Thus, the presence of water environment significantly modifies the radiation resistance of the initial complex organic molecules: it enhances radiosensitivity and destruction of pyridine, with implications for radiobiology and astrochemistry.