Dynamics of Hyperthermal Energy Ion-Surface Collisions: Dissociative and non-dissociative Scattering of Ethanol cations from a Self-Assembled Monolayer Surface of Fluorinated Alkyl Thiol on Au (111)
- BATTELLE (PACIFIC NW LAB)
Dissociation and inelastic scattering of ethanol molecular ions from self-assembled monolayers (SAM) surface of fluorinated alkyl thiol on an Au (111) monocrystal have been studied at 28.9 and 52.9 eV collision energies. A single dynamics mechanism for quasi0inelastic scattering was found at both energies. Ions recoil nearly parallel to the surface with very small kinetic energy losses of the order of < 2 eV. Dissociation dynamics features for the main dissociation channel, loss of methyl radical, are dramatically different from that of inelastically scattered primary ions and are different at the two collision energies studies. At 28.9 eV two energetically and angularly resolved features are observed, one corresponding to the loss of very large amounts (nearly all) of ions translational energy and the other appearing to gain energy (superelastic scattering). This implies a lifetime of such excited ions of more than 5s. The same dynamics features are observed at 52.9 eV ion energy except that a second inelastic process begins to compete with the nearly fully inelastic process. Moreover, at this energy the delayed ion dissociation mechanism is the dominant mechanism. The hypothesis that collision of ethanol cations useful rationale for the observed dynamics. Support for this hypotheses is provided by Newton diagrams, which summarize momentum conservation relationships in terms of a common center-of-mass, cmeff, which provides a basis for describing different ion-surface interactions contributing to surface-induced dissociation of ethanol ions. Preliminary experiments with Ar+ scattered from the same surface exhibit very similar dynamics features to the observed for ethanol cations. Finally, we note that intensities of scattered primary or fragment ions never approach the specular angle at the energies investigated here.
- Research Organization:
- Pacific Northwest National Lab., Richland, WA (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 15005577
- Report Number(s):
- PNNL-SA-36974; TRN: US0305572
- Journal Information:
- International Journal of Mass Spectrometry, Vol. 223, Issue 1-3; Other Information: PBD: 15 Jan 2003
- Country of Publication:
- United States
- Language:
- English
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