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  • SOFT X-RAY IRRADIATION OF M...
    Chen, Y-J; CIARAVELLA, A; CARO, G M MUNOZ; CECCHI-PESTELLINI, C; Jimenez-Escobar, A; Juang, K-J; Yih, T-S

    The Astrophysical journal, 12/2013, Letnik: 778, Številka: 2
    Journal Article

    Pure methanol ices have been irradiated with monochromatic soft X-rays of 300 and 550eV 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 absorbed eV in the X-ray experiments has been compared to those obtained with electron and ultraviolet (UV) irradiation experiments.