XUV photodesorption of carbon cluster ions and ionic photofragments from a mixed methane–water ice. Issue 11 (28th February 2018)

• Record Type: Journal Article
• Authors: Suhasaria, T.; Thrower, J. D.; Frigge, R.; Roling, S.; Bertin, M.; Michaut, X.; Fillion, J.-H.; Zacharias, H.
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 11(2018)
• Page Start: 7457
• Page End: 7469
• Publication Date: 2018-02-28
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp00171e
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The photochemical processing of a CH4 : D2 O 1 : 3.3 ice mixture adsorbed on a HOPG surface in the XUV regime was investigated using pulses obtained from the Free-electron LASer in Hamburg (FLASH) facility. Abstract : The photochemical processing of a CH4 : D2 O 1 : 3.3 ice mixture adsorbed on an HOPG surface in the XUV regime was investigated using pulses obtained from the Free-electron LASer in Hamburg (FLASH) facility. Ice films were exposed to femtosecond pulses with a photon energy of hν = 40.8 eV, consistent with the HeII resonance line. Cationic species desorbing directly from the ice films were detected using time-of-flight (ToF) mass spectrometry. Simple ions formed through the fragmentation of the parent molecules and subsequent recombination reactions were detected and are consistent with efficient D + and H + ejection from the parent species, similar to the case for low energy electron irradiation. The FEL fluence dependencies of these ions are linear or exhibit a non-linear order of up to 3. In addition, a series of C n + cluster ions (with n up to 12) were also identified. These ions display a highly non-linear desorption yield with respect to the FEL fluence, having an order of 6–10, suggesting a complex multi-step process involving the primary products of CH4 fragmentation. Two-pulse correlation measurements were performed to gain further insight into the underlying reaction dynamics of the photo-chemical reactions. The yield of the D2 O derived products displayed a different temporal behaviour with respect to the C n + ions, indicating the presence of very different reaction pathways to the two families of ionic products.