| Project/Area Number |
16340116
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
原子・分子・量子エレクトロニクス・プラズマ
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| Research Institution | University of Electro-Communications |
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Principal Investigator |
SHIMIZU Kazuko University of Electro-Communications, Dep.of Applied Physics and Chemistry, Professor (30017446)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEDA Mitsuo Univ. of Electro-Communications, Dep.of Information and Communication Engineering, Professor (00114926)
MORINAGA Makoto Univ. of Electro-Communications, Institute for Laser Science, Assistant Professor (60230140)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥10,900,000 (Direct Cost: ¥10,900,000)
Fiscal Year 2006: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2005: ¥5,400,000 (Direct Cost: ¥5,400,000)
Fiscal Year 2004: ¥3,700,000 (Direct Cost: ¥3,700,000)
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| Keywords | quantum reflection / metastable rare gas atoms / laser cooling / magneto-optical trap / Fresnel diffraction / van der Waals potential / 準安定状態ヘリウム / 磁気反射 / 原子光学 / 固体表面ポテンシャル / 低速原子ビーム |
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| Research Abstract |
We studied the quantum reflection of the metastable helium atoms on a flat polished silicon surface. We measured the reflectivity as a function of the normal incident velocity component between 3 and 30 cm/s, and confirm that on a flat surface the reflection of atoms is caused by the attractive van der Waals potential. In our case the atoms are mainly reflected in a region where the retardation effect leads to a potential of the approximate form, U(z)=-C_4/z^4 where z is the distance from the surface. We also studied the reflection and diffraction on surface structures consisting of parallel narrow ridges. The structure consists of wall-like ridges at a distance of L=5μm and with a width at the top of l=100nm. We observed on this structure an increase of the reflectivity by two orders of magnitude, exceeding 10% for normal incident velocities below about 25cm/s. At grazing incidence even fast atoms of 100m/s can be reflected very efficiently at such a surface structure.
In order to quantitatively describe our data, we have developed a theoretical description of the reflection and scattering of atomic waves from our surface structures. As a first approximation we can assume that the van der Waals constant is reduced by a factor l/L, where l is the size at the top of the ridges and L the distance between the ridges. The reflectivity on the ridges structures then follows immediately from the scaling law of the quantum reflection. Deviations appear when the ratio l/L is very small. In the limiting case of l/L→0, i.e. of idealized thin ridges, a new interesting effect can be observed: The atomic wave is reflected due to the Fresnel diffraction at the array of ridges.
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