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Title: Soft X-ray irradiation of methanol ice: Formation of products as a function of photon energy

Pure methanol ices have been irradiated with monochromatic soft X-rays of 300 and 550 eV close to the 1s resonance edges of C and O, respectively, and with a broadband spectrum (250-1200 eV). The infrared (IR) spectra of the irradiated ices show several new products of astrophysical interest such as CH{sub 2}OH, H{sub 2}CO, CH{sub 4}, HCOOH, HCOCH{sub 2}OH, CH{sub 3}COOH, CH{sub 3}OCH{sub 3}, HCOOCH{sub 3}, and (CH{sub 2}OH){sub 2}, as well as HCO, CO, and CO{sub 2}. The effect of X-rays is the result of the combined interactions of photons and electrons with the ice. A significant contribution to the formation and growth of new species in the CH{sub 3}OH ice irradiated with X-rays is given by secondary electrons, whose energy distribution depends on the energy of X-ray photons. Within a single experiment, the abundances of the new products increase with the absorbed energy. Monochromatic experiments show that product abundances also increase with the photon energy. However, the abundances per unit energy of newly formed species show a marked decrease in the broadband experiment as compared to irradiations with monochromatic photons, suggesting a possible regulatory role of the energy deposition rate. The number of new molecules produced per absorbedmore » eV in the X-ray experiments has been compared to those obtained with electron and ultraviolet (UV) irradiation experiments.« less
Authors:
; ;  [1] ; ;  [2] ; ;  [3]
  1. Department of Physics, National Central University, Jhongli City, Taoyuan County 32054, Taiwan (China)
  2. INAF-Osservatorio Astronomico di Palermo, P.za Parlamento 1, I-90134 Palermo (Italy)
  3. Centro de Astrobiología (INTA-CSIC), Carretera de Ajalvir, km 4, Torrejón de Ardoz, E-28850 Madrid (Spain)
Publication Date:
OSTI Identifier:
22341892
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ASTROPHYSICS; CARBON DIOXIDE; CARBON MONOXIDE; ELECTRONS; ENERGY ABSORPTION; ENERGY LOSSES; ENERGY SPECTRA; INFRARED SPECTRA; INTERACTIONS; IRRADIATION; METHANOL; MOLECULES; MONOCHROMATIC RADIATION; PHOTONS; RESONANCE; SOFT X RADIATION; ULTRAVIOLET RADIATION