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

Abstract

Methanol (CH3OH) is one of the most abundant organic molecules in astrophysical environments. It has been found in cold regions such as surfaces of comets, ices near young stellar objects and protoplanetary disks, as well as in the gas phase in different regions in space. In this work, we experimentally simulate the methanol ice and its behavior when irradiated by broadband soft X-rays. The experiments were performed at the Brazilian Synchrotron Facility LNLS/CNPEM, employing a broadband photon beam (6 to 2000 eV). The frozen sample was analyzed in situ by infrared spectroscopy (IR) in simulated astrophysical at different radiation fluences. The results show the formation of several new species such as CO2, CO, H2O and CH4 during the photolysis CH3OH ice by soft X-rays. We determined effective destruction and formation cross-section, as well as the chemical equilibrium fluence (FE) and desorption yields. The timescale to reach chemical equilibrium in some astrophysical environments with soft X-rays were estimated. The result helps us to understand the photolysis induced by X-rays in organic-rich ices in space environments.

Keywords

• experimental astrochemistry
• astrophysical ices
• methanol
• X-rays
• desorption
• photolysis
• synchrotron radiation