Processing of formic acid-containing ice by heavy and energetic cosmic ray analogues

Abstract

Formic acid (HCOOH) has been extensively detected in space environments,\nincluding interstellar medium (gas and grains), comets and meteorites. Such\nenvironments are often subjected to the action of ionizing agents, which may\ncause changes in the molecular structure, thus leading to formation of new\nspecies. Formic acid is a possible precursor of pre-biotic species, such as\nGlycine (NH2CH2COOH). This work investigates experimentally the physicochemical\neffects resulting from interaction of heavy and energetic cosmic ray analogues\n(46MeV 58Ni11+) in H2O:HCOOH (1:1) ice, at 15 K, in ultrahigh vacuum regime,\nusing Fourier transform infrared spectrometry in the mid-infrared region\n(4000-600 cm-1 or 2.5-12.5 microns). After the bombardment, the sample was\nslowly heated to room temperature. The results show the dissociation\ncross-section for the formic acid of 2.4x10^-13 cm2, and half-life due to\ngalactic cosmic rays of 8x10^7 yr. The IR spectra show intense formation of CO\nand CO2, and small production of more complex species at high fluences.\n