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| | over the counter std test; [http://www.ubi-cation.com/ubication/node/6056 My Site], title of the writer is Numbers but it's not the most masucline title out there. For years I've been working as a payroll clerk. Her family members lives in Minnesota. Doing ceramics is what my family and I enjoy. |
| [[File:ARPESgeneral.png|thumb|An Experimental Setup of Angle-Resolved Photoemission Spectroscopy]]
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| '''Angle-resolved photoemission spectroscopy''' ('''ARPES'''), also known as '''ARUPS''' (angle-resolved [[ultraviolet]] [[photoemission spectroscopy]]), is a direct experimental technique to observe the distribution of the [[electrons]] (more precisely, the density of single-particle electronic excitations) in the [[reciprocal space]] of solids. ARPES is one of the most direct methods of studying the electronic structure of the surface of solids.
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| ARPES gives information on the direction, speed and scattering process of [[valence electrons]] in the sample being studied (usually a solid). This means that information can be gained on both the energy and momentum of an electron, resulting in detailed information on band dispersion and [[Fermi surface]]. This technique is a refinement of ordinary [[photoemission spectroscopy]].
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| From conservation of energy, we have
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| :<math> E = \hbar \omega - E_{k_f} - \phi. </math> | |
| where E is the binding energy of the electron. Photon momentum is often neglected because of its smallness compared with electron momentum.
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| In the typical case, where the surface of the sample is smooth, translational symmetry requires that the component of electron momentum in the plane of the sample be conserved:
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| :<math> \hbar k_{i\parallel}=\hbar k_{f\parallel}=\sqrt{2m E_f}\sin\theta</math>
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| where
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| *<math> E_{k_f} = </math> kinetic energy of the outgoing electron — measured.
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| *<math> \hbar \omega = </math> incoming photon energy — measured.
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| *<math> \phi = </math> electron [[work function]] (energy required to remove electron from sample to vacuum)
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| *<math>\hbar k_f=</math> momentum of the outgoing electron, measured by angle
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| *<math>\hbar k_i=</math> initial momentum of the electron
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| {{Condensed matter experiments}}
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| However, the normal component of electron momentum <math>k_{i\perp}</math> might not be conserved. The typical way of dealing with this is to assume that the final in-crystal states are free-electron-like, in which case one has
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| :<math>k_{i\perp}=\frac{1}{\hbar}\sqrt{2m(E_f \cos^2\theta+V_0)}</math>
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| in which <math>V_0</math> denotes the band depth from vacuum, including electron work function <math>\phi</math>; <math>V_0</math> can be determined by examining only the electrons emitted perpendicular to the surface, measuring their kinetic energy as a function of incident photon energy.
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| The equations for energy and momentum can be solved to determine the dispersion relation between the binding energy, <math> E </math>, and the wave vector, <math> \mathbf{k}_i=\mathbf{k}_{i\parallel}+\mathbf{k}_{i\perp} </math>, of the electron.
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| == See also ==
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| *[[Laser-based angle-resolved photoemission spectroscopy]]
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| == External links ==
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| * Andrea Damascelli, "Probing the Electronic Structure of Complex Systems by ARPES", ''Physica Scripta'' '''T109''', 61-74 (2004) [http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Reviews/ARPES_intro.pdf]
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| {{DEFAULTSORT:Arpes}}
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| [[Category:Condensed matter physics]]
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| [[Category:Condensed matter stubs]]
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| [[Category:Emission spectroscopy]]
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| {{Physics-stub}}
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| {{Condensedmatter-stub}}
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