
Angleresolved photoemission spectroscopy (ARPES), is a direct experimental technique to observe the distribution of the electrons (more precisely, the density of singleparticle electronic excitations) in the reciprocal space of solids. The technique is a refinement of ordinary photoemission spectroscopy, studying photoemission of electrons from a sample achieved usually by illumination with soft Xrays. ARPES is one of the most direct methods of studying the electronic structure of the surface of solids. 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. The technique is also known as ARUPS (angleresolved ultraviolet photoemission spectroscopy) when using ultraviolet light (as opposed to Xrays) to generate photoemission. ==Theory== From conservation of energy, we have :$E\; =\; \backslash hbar\; \backslash omega\; \; E\_\; \; \backslash phi.$ where E is the binding energy of the electron. Photon momentum is often neglected because of its relatively small contribution compared with electron momentum. 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: :$\backslash hbar\; k\_=\backslash hbar\; k\_=\backslash sqrt\backslash sin\backslash theta$ where *$E\_\; =$ kinetic energy of the outgoing electron — measured. *$\backslash hbar\; \backslash omega\; =$ incoming photon energy — measured. *$\backslash phi\; =$ electron work function (energy required to remove electron from sample to vacuum) *$\backslash hbar\; k\_f=$ momentum of the outgoing electron, measured by angle *$\backslash hbar\; k\_i=$ initial momentum of the electron However, the normal component of electron momentum $k\_$ might not be conserved. The typical way of dealing with this is to assume that the final incrystal states are freeelectronlike, in which case one has :$k\_=\backslash frac\backslash sqrt$ in which $V\_0$ denotes the band depth from vacuum, including electron work function $\backslash phi$; $V\_0$ can be determined by examining only the electrons emitted perpendicular to the surface, measuring their kinetic energy as a function of incident photon energy. The equations for energy and momentum can be solved to determine the dispersion relation between the binding energy, $E$, and the wave vector, $\backslash mathbf\_i=\backslash mathbf\_+\backslash mathbf\_$, of the electron. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Angleresolved photoemission spectroscopy」の詳細全文を読む スポンサード リンク
