Astrophysical Icy Surface Simulation under Energetic Particles and Radiation Field in Formic Acid

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• 作者：D. P. P. Andrade ; H. M. Boechat-Roberty ; E. F. da Silveira ; S. Pilling ; P. Iza ; R. Martinez ; L. S. Farenzena ; M. G. P. Homem ; M. L. M. Rocco
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：August 7, 2008
• 年：2008
• 卷：112
• 期：31
• 页码：11954-11961
• 全文大小：265K
• 年卷期：v.112,no.31(August 7, 2008)
• ISSN：1932-7455

文摘

In this work, the fragmentation, survival, and chemical reactions of formic acid (HCOOH) molecules condensed at 56 K are analyzed using plasma desorption mass spectrometry (PDMS) and photon-stimulated ion desorption (PSID) in an effort to simulate the effects of energetic charged particles (e.g., cosmic rays) and radiation fields on interstellar/cometary ices. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing soft X-ray photons (535.1 eV) and energetic ions (∼65 MeV) obtained as ²⁵²Cf fission fragments. Mass spectra of positive and negative desorbed ions were obtained using a time-of-flight (TOF) spectrometer, providing information on the fragmentation pattern and abundance of the ionic species released from the icy surface. In both techniques, the major contribution to the released/desorbed ions were positively charged fragments. The production of several series of clusters, some of them with mass/charge ratios of up to 500 u/e, was observed in the PDMS spectra. Comparison between the employed techniques (photon and ion impacts) indicates that the interaction of energetic ions with formic acid ice produces a greater variety of ions than soft X-ray photon impact. This suggests that cosmic rays and high-energy solar wind particles, despite its reduced flux compared to other lower-energy particles, might play an important role in the synthesis of prebiotic molecules.