Photoelectrochemical process
[1] These processes apply to photochemistry, optically pumped lasers, sensitized solar cells, luminescence, and photochromism.
Photoexcitation is exploited in dye-sensitized solar cells, photochemistry, luminescence, optically pumped lasers, and in some photochromic applications.
In chemistry, photoisomerization is molecular behavior in which structural change between isomers is caused by photoexcitation.
Photoisomerizable molecules are already put to practical use, for instance, in pigments for rewritable CDs, DVDs, and 3D optical data storage solutions.
Two major classes are trans-cis (or 'E-'Z) conversion, and open-closed ring transition.
Photoionization is the physical process in which an incident photon ejects one or more electrons from an atom, ion or molecule.
But with the development of pulsed lasers it has become possible to create extremely intense, coherent light where multi-photon ionization may occur.
This probability decreases rapidly with the number of photons required, but the development of very intense, pulsed lasers still makes it possible.
In the perturbative regime (below about 1014 W/cm2 at optical frequencies), the probability of absorbing N photons depends on the laser-light intensity I as IN .
The electrons released from the target will have approximately an integer number of photon-energies more kinetic energy.
The dipole forms owing to the difference of mobilities (or diffusion constants) for holes and electrons which combined with the break of symmetry provided by the surface lead to an effective charge separation in the direction perpendicular to the surface.
Therefore, this is a single unit of EM radiation that is equal to the Planck constant (h) times the frequency of light.
The photochemical equivalence law applies to the part of a light-induced reaction that is referred to as the primary process (i.e. absorption or fluorescence).
[13] In physics, absorption of electromagnetic radiation is the way by which the energy of a photon is taken up by matter, typically the electrons of an atom.
In particular this process is commonly employed where reactions require light sources of certain wavelengths that are not readily available.
[14] Cadmium; some of the noble gases, for example xenon; zinc; benzophenone; and a large number of organic dyes, are also used as sensitizers.
A good example is this: When an alkaline solution of sodium hypochlorite and a concentrated solution of hydrogen peroxide are mixed, a reaction occurs: O2*is excited oxygen – meaning, one or more electrons in the O2 molecule have been promoted to higher-energy molecular orbitals.
It can do that in more than one way: The intensity, duration and color of emitted light depend on quantum and kinetical factors.
However, excited molecules are frequently less capable of light emission in terms of brightness and duration when compared to sensitizers.
The energy is stored through means of quantum vibration, so sensitizers are usually compounds which either include systems of aromatic rings or many conjugated double and triple bonds in their structure.
