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Title: The interaction of fast neutral atoms with metal surfaces
Author: Yusuf, Mohd Nor bin Md
ISNI:       0000 0001 3576 3751
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1989
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The interactions of fast neutral atoms (Hz , He, Ne, N2 and Ar) in the energy range of 200 eV to 7 keV on polycrystalline gold and lithium surfaces have been studied under UHV conditions. It was found that the majority of the secondary electrons formed in the interactions have low energy (1-3 eV), and the spectra have structure which shows no evidence of any significant effect of beam type and target temperature. The electrons are ejected into a solid angle around the surface normal in a "near cosine” angular distribution. With the aid of a thermistor-based absolute bolometer of new design, the secondary electron yield coefficient was found to increase linearly with the fast atom energy, and dependent on the projectile's atomic number the larger the value. The variation of the yield with angle of incidence θ1 deviates slightly from the sec (θ1) law, which suggests that the majority of the electrons are formed deep under the surface. In the step of collision with the gold surface, a small fraction of the fast neutral atoms are ionised, for which it is believed to be a result of an electron promotion mechanism. It is found that for the ionisation to occur the fast neutrals must have energy larger than a threshold of about 350 eV. In the case of the lithium surface, the fast atoms also cause ejection of neutral Li atoms and slow Li- ions (≈ 10 eV). A series of computer simulations of rainbow peak scattering of fast He atoms from a two atom unreconstructed clean Cu{lll} surface has been carried out using a Born- Mayer repulsive potential V(r) = A exp ( -br); a good fit with the experimental data can be achieved with A = 1805 eV and b = 4.14 A-1.
Supervisor: Not available Sponsor: Jabatan Perkhidmatan Awam, Malaysia ; Universiti Teknologi Malaysia
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics