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SUMMARY:Surface dynamics in the low friction regime: Xe on Pt(111) using 3
 He Spin Echo Spectroscopy - D.J. Ward\, SMF Cavendish Laboratory
DTSTART:20071025T153000Z
DTEND:20071025T160000Z
UID:TALK8401@talks.cam.ac.uk
CONTACT:Stephen Walley
DESCRIPTION:The dynamics of Xenon on Platinum (111) have been measured usi
 ng the 3He spin-echo (3HeSE) spectrometer\, recently developed in our grou
 p [1\, 2]. 3HeSE has given a significant improvement in energy resolution 
 for the measurement of surface dynamics. In this study we take advantage o
 f this development to fully characterise the system of Xe on Pt(111) which
  has previously been only partially accessible\, leaving perplexing questi
 ons. \nA previous time of flight\, quasielastic helium atom scattering (QH
 AS) study presented evidence for a fully mobile two-dimensional gas at low
  coverage [3]. In the present work\, we perform a detailed\, lineshape ana
 lysis of the quasielastic scattering to reveal evidence for two dynamic pr
 ocesses of isolated Xe species. Diffusion as a two dimensional gas is appa
 rent\, which supports the previous study.  However\, we also find evidence
  of an activated jump diffusion process.  The signature for jump diffusion
  is demonstrated by a second\, and significantly narrower\, broadening in 
 the energy spectrum. The jump diffusion component can be resolved in the p
 resent work due to the improved resolution of 3HeSE over QHAS. Using the l
 ow friction previously predicted [4]\, we suggest that Xe settles into pre
 ferred sites with finite lifetime and when activated travels relatively la
 rge distances across the potential energy surface.\n\n[1]	 A.P. Jardine\, 
 S. Dworski\, P. Fouquet\, G. Alexandrowicz\, D. J. Riley\, G. Y. H. Lee\, 
 J. Ellis\, W. Allison\, Science 304\, 1790-1793 (2004).\n[2]	P. Fouquet\, 
 A.P. Jardine\, S. Dworski\, G. Alexandrowicz\, W. Allison\, and J. Ellis\,
  Rev. Sci. Instrum. 76\, 053109 (2005).\n[3]	J.Ellis\, A.P. Graham\, J.P.T
 onnies\, Phys. Rev. Lett. 82\, 5072-5075 (1999).\n[4]	B.N.J. Persson and A
 . Nitzan\, Surf. Sci. 367\, 261 (1996)\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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