Excitation (physical)
In Physical, one calls excitation any phenomenon which leaves a system its at-rest state to bring it in a state of higher energy. The system is then in a excited state . This concept is particularly used in Quantum physics, for which the atoms have quantum states associated with energy levels: a system is in an excited level when its energy is higher than that of the fundamental state.
Excited electron
General information
A excited electron is a electron which has a potential energy higher than bare essential.The electrons in the Atome S are so small that in fact the rules of the quantum Mécanique count for them. One of the most important consequences in is that they cannot have any energy, but that according to the position of the atom and other atoms of the Orbite S are formed for the electrons, with each one a discrete potential energy. Each orbit can contain two electrons precisely. Under normal conditions, the electrons always will seek the orbit which with the potential energy lowest.
When an electron gains energy , for example while absorbing the energy of a Photon, it can jump of its orbit to an orbit having a higher potential energy. An electron in this state is called excited electron . This state of excitation is not a stable condition for an electron and cannot thus last a long time: since a lower orbit is available, the electron - at a given moment - will turn over itself to the orbit having a smaller potential energy. It then will return to the environment the energy which it had gained, in the form of a photon, of heat,…
Generally, the passage to an orbit of lower energy is done at a speed flash. But sometimes, this passage is - according to quantum mechanics - prohibited ; in this case, the return of the electron to the lower orbit can last very a long time, surely several seconds but even several minutes in certain cases. This effect is called Phosphorescence and is e.a. used to manufacture toys glow in the dark (which emit light in the black during a certain time).
The differences in energy between the orbits furthest away from the core of the atom are about some eV (electronvolt S). The photons which correspond to it can have a wavelength of light visible. This effect is used EP in the lamps LED S and the Laser S.
The differences in energy between the orbits closest to the core in the heavier atoms (EP of metals like the Iron, the Copper and the Molybdenum) are thousands of times more important (sometimes until tens of thousands of electronvolts). The photons which correspond to it have a wavelength of the field of x-rays.
Excited level
The excited level is the level where a electron is after the absorption of a Photon. While emitting the absorptive photon, the electron can return from the excited level on its starting level.First of all let us present the context in which we will base ourselves, that is to say the Atome of Hydrogène.
The model of the hydrogen atom is a electron orbits about it around a core, made up of a Proton. It is the simplest atom which exists. The electrons are with precise distances from the core. At rest, when n=1, the orbit of the electron has a ray of 10-11 meter (called traditional ray of Bohr). The electron can also be on larger orbits, associated with integers N = 2,3,4,…, ∞ (= infinite)
The core with a ray of 10-15 meter. The atom at rest is 10.000 times larger than the core. If the core had the size of a ball, the atom would have the size of the Place of the Harmony.
Thus, the atom can pass from the fundamental state (n=1 where N is the number of electrons) in an excited state by absorbing a Photon Lumière. It can also return to its fundamental state by emitting Lumière whose Couleur (Wavelength) will depend on the energy levels of the atom.
The passage of the level on the level corresponds to a emission/absorption of Wavelength lambda, such as , with .
If the atom receives sufficient energy, the electron passes from the level N = 1 on the level = infinite. The atom loses its single electron then and becomes a Cation is a positive Ion. The wavelength corresponding is 0,91.10-6 m is Ultraviolet.
In the atmosphere of a star, the hydrogen atoms, lit by star, only the colors absorb which make them pass from a level to another.
See too
Related articles
- Bohr atom
- Spectrum of excitation
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