LABORATORY INVESTIGATION OF X-RAY PHOTOLYSIS OF ETHANOL ICE AND ITS IMPLICATION ON ASTROPHYSICAL ENVIRONMENTS

Abstract

Here we present experimental results on the irradiation of ethanol ice (CH3CH2OH) by broadband soft X-rays to simulate the effect processing of organic-rich astrophysical ices by space radiation. This molecule was detected in the interstellar medium in molecular clouds like Sagittarius B2 and towards nebulas like Orion KL. The experiments were performed at the Brazilian Synchrotron Facility LNLS/CNPEM, at Campinas, SP. The frozen sample was analyzed in-situ by infrared spectroscopy (IR) in a simulated astrophysical environment at different radiation fluences. The results show the formation of several new molecular species such as CO2, CO, H2O, CH4, CH3(CO)CH3 (acetone), and CH3COOH (acetic acid). We determined the effective destruction cross-section of ethanol (~1×10-18 cm2) and the formation cross-sections of the daughter species with values between 0.5 to 3.4×10-18 cm2. The chemical equilibrium phase of ice was characterized and desorption yield induced by X-rays was determined (0.13 molecules photon-1). The result helps us to understand the photolysis induced by X-rays in organic-rich ices in space environments.

Keywords

• experimental astrochemistry
• astrophysical ices
• ethanol
• x-rays
• desorption
• synchrotron radiation