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The effect of broadband soft X-rays in SO2-containing ices: Implication on the photochemistry of ices towards young stellar objects | | S. Pilling
; A. Bergantini
; | | Date: |
1 Sep 2015 | | Abstract: | We investigate the effects produced mainly by broadband soft X-rays up to 2
keV (plus fast (keV) photoelectrons and low-energy (eV) induced secondary
electrons) in the ice mixtures containing H2O:CO2:NH3:SO2 (10:1:1:1) at two
different temperatures (50 K and 90 K). The experiments are an attempt to
simulate the photochemical processes induced by energetic photons in
SO2-containing ices present in cold environments in the ices surrounding young
stellar objects (YSO) and in molecular clouds in the vicinity of star-forming
regions, which are largely illuminated by soft X-rays. The measurements were
performed using a high vacuum portable chamber from the Laboratorio de
Astroquimica e Astrobiologia (LASA/UNIVAP) coupled to the spherical grating
monochromator (SGM) beamline at the Brazilian Synchrotron Light Source (LNLS)
in Campinas, Brazil. In-situ analyses were performed by a Fourier transform
infrared (FTIR) spectrometer. Sample processing revealed the formation of
several organic molecules, including nitriles, acids, and other compounds such
as H2O2, H3O+, SO3, CO, and OCN-. The dissociation cross section of parental
species was in the order of 2-7E-18 cm2. The ice temperature seems not to
affect the stability for SO2 in the presence of X-rays. Formation cross
sections of produced new species were also determined. Molecular half-lives at
ices towards YSOs due to the presence of incoming soft X-rays were estimated.
The low obtained values, employing two different models of radiation field of
YSOs (TW Hydra and typical T Tauri star), reinforce that soft X-rays are indeed
a very efficient source of molecular dissociation in such environments. | | Source: | arXiv, 1509.0237 | | Services: | Forum | Review | PDF | Favorites | |
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