Surface science investigations of photoprocesses in model interstellar ices
A cartoon illustrating the potential range of processes that might occur within a PAH doped water ice matrix subject to irradiation with UV photons. The inset shows a molecular scale cartoon of a surface bound benzene and its associated hydrogen-bonded cluster, the unimolecular decomposition of which yields the hot benzene, and water in the gas phase. Dust grain image adapted from http://presolar.wustl.edu/work/idp.html
ToF profiles of (a) benzene and (b) water desorption for varying layer configurations, following excitation at with per pulse of optical energy. Thin gray lines: raw data; thick lines: single component M-B fits. Profiles have been offset for clarity.
Cartoon summarizing the expected morphology of the layers of ice in each of the deposition configurations studied (not to scale). (a) S/W/B system: water wets the surface of the sapphire; the thinner layer of benzene does not wet the water and forms islands on its rough surface. (b) S/B/W system: the thin layer of benzene does not wet the sapphire; the thicker overlayer of water does not wet the surface of the thin benzene layer.
(a) ToF profiles of benzene desorption from the S/B system as a function of photon wavelength at an optical power of per pulse; thin gray lines: raw data; thick lines: M-B fits, one component fixed at , one free component, and the sum of the two components. (b) ToF profiles of water desorption from the S/W/B system as a function of photon wavelength at an optical power of per pulse; thin gray lines: raw data; thick lines: single component M-B fits. Profiles have been offset for clarity.
Extended ToF profiles of water desorption, (a) from varying layer configurations at (pulse ), and (b) from the S/B/W system at varying wavelength (pulse ). Thin gray lines: raw data; thick lines: 48 point adjacent average smoothed data.
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