WebAn electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode-ray tubes (CRTs), used in nearly all television sets, computer displays and oscilloscopes that are not flat-panel displays.

WebIn physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they came.It is usually a diffuse reflection due to scattering, as opposed to specular reflection as from a mirror, although specular backscattering can occur at normal incidence with a surface.Backscattering has important applications in …

WebA dynamical system may be defined formally as a measure-preserving transformation of a measure space, the triplet (T, (X, Σ, μ), Φ).Here, T is a monoid (usually the non-negative integers), X is a set, and (X, Σ, μ) is a probability space, meaning that Σ is a sigma-algebra on X and μ is a finite measure on (X, Σ).A map Φ: X → X is said to be Σ-measurable if …

WebThe Greek letter π in their name refers to p orbitals, since the orbital symmetry of the pi bond is the same as that of the p orbital when seen down the bond axis. One common form of this sort of bonding involves p orbitals themselves, though d orbitals also engage in pi bonding. This latter mode forms part of the basis for metal-metal multiple bonding.

WebCompton scattering, discovered by Arthur Holly Compton, is the scattering of a high frequency photon after an interaction with a charged particle, usually an electron.If it results in a decrease in energy (increase in wavelength) of the photon (which may be an X-ray or gamma ray photon), it is called the Compton effect.Part of the energy of the photon is …

WebA quantum jump is the abrupt transition of a quantum system (atom, molecule, atomic nucleus) from one quantum state to another, from one energy level to another. When the system absorbs energy, there is a transition to a higher energy level (); when the system loses energy, there is a transition to a lower energy level.The concept was introduced by …

WebPlasma oscillations, also known as Langmuir waves (after Irving Langmuir), are rapid oscillations of the electron density in conducting media such as plasmas or metals in the ultraviolet region. The oscillations can be described as an instability in the dielectric function of a free electron gas.The frequency only depends weakly on the wavelength of the …

WebK-alpha emission lines result when an electron transitions to a vacancy in the innermost "K" shell (principal quantum number n = 1) from a p orbital of the second, "L" shell (n = 2), leaving a vacancy there.By posing that initially in the K shell there is a single vacancy (and, hence, a single electron is already there), as well as that the L shell is not entirely empty …

WebIn solid-state physics, the nearly free electron model (or NFE model) or quasi-free electron model is a quantum mechanical model of physical properties of electrons that can move almost freely through the crystal lattice of a solid. The model is closely related to the more conceptual empty lattice approximation.The model enables understanding and …

WebShot noise or Poisson noise is a type of noise which can be modeled by a Poisson process.. In electronics shot noise originates from the discrete nature of electric charge.Shot noise also occurs in photon counting in optical devices, where shot noise is associated with the particle nature of light.

WebUn microscopio electrónico de transmisión (TEM por su sigla en inglés, o MET en español) es un microscopio que utiliza un haz de electrones para visualizar un objeto, debido a que la potencia amplificadora de un microscopio óptico está limitada por la longitud de onda de la luz visible. Lo característico de este microscopio es el uso de una muestra ultrafina y que …

WebOptical transitions. Most molecules and ions absorb energy in the ultraviolet or visible range, i.e., they are chromophores. The absorbed photon excites an electron in the chromophore to higher energy molecular orbitals, giving rise to an excited state. For organic chromophores, four possible types of transitions are assumed: π–π*, n–π*, σ–σ*, and n–σ*.

WebIn physics and chemistry, ionization energy (IE) (American English spelling), ionisation energy (British English spelling) is the minimum energy required to remove the most loosely bound electron of an isolated gaseous atom, positive ion, or molecule. The first ionization energy is quantitatively expressed as X(g) + energy X + (g) + e −. where X is any atom or …

WebHigh-resolution transmission electron microscopy is an imaging mode of specialized transmission electron microscopes that allows for direct imaging of the atomic structure of samples. It is a powerful tool to study properties of materials on the atomic scale, such as semiconductors, metals, nanoparticles and sp 2-bonded carbon (e.g., graphene, C …