1998 Fiscal Year Final Research Report Summary
Atomic layer structrure analysis by super-sonic molecular beam techniques.
| Project/Area Number |
07405002
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
表面界面物性
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| Research Institution | Institute of Applied Physics, The University of Tsukuba |
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Principal Investigator |
YAMAMOTO Shigehiko The University of Tsukuba Institute of Applied Phsycs Professor, 物理工学系, 教授 (60251039)
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| Project Period (FY) |
1995 – 1998
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| Keywords | Molecular Beam / Dissociation / Adsorption / Pt (111) / LiF (100) / Hard Cube Model / Washboard Model / Ultra high vacuum |
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| Research Abstract |
In this project we have built a new super-sonic molecular beam machine which is capable of studying the dynamics of chemical reactions as well as analyzing the structure of various surfaces. The energy dispersion of 6% and the angular resolution of less than 0.50 of our machine enable us to determine the energy - momentum dispersion relation of the surface phonon generated at the LiF(100) surface.
Helium Atom Scattering (HAS) technique is used in studying dissociative adsorption of methane and ethane molecules at a Pt(111) surface. It has been revealed that such alkane molecules as methane and ethane with high enough energy dissociatively adsorb on the Pt(111) surface via intermediates which decompose into carbon and hydrogen at the surface temperature above 600K.The intermediate is found to be ethyldine moiety via methyl moiety.
Molecules with such high kinetic energy that Eley-Redeal reaction process is dominant directly are known to decompose into fragments when they collide with metal surfaces. During such collisions, impinging molecules dissipate their kinetic energy by creating phonon s in the solid (direct inelastic collision channel) as well as by exciting internal modes of their own molecules (internal mode excitation channel). In the case of methane molecules with kinetic energy ranging from 300 to 700 meV, our time of flight (TOP) measurements of reflected molecules from a Pt(111) surface have shown no sign of internal mode excitation.
Based on TOF and angular intensity distribution measurements of reflected methane molecules from such a flat surface as Pt(111), it is found that direct inelastic collision can be qualitatively explained by the classical Hard Cube Model. It is also found that Washboard model is more appropriate to explain the collision at rough a rough surface such as LiF(100).
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