Photons that excite electrons to a higher energy level in an atom
Photoexcitation in crystal
Photoexcitation is the production of an excited state of a quantum system by photon absorption. The excited state originates from the interaction between a photon and the quantum system. Photons carry energy that is determined by the wavelengths of the light that carries the photons.[1] Objects that emit light with longer wavelengths, emit photons carrying less energy. In contrast to that, light with shorter wavelengths emit photons with more energy. When the photon interacts with a quantum system, it is therefore important to know what wavelength one is dealing with. A shorter wavelength will transfer more energy to the quantum system than longer wavelengths.
On the atomic and molecular scale photoexcitation is the photoelectrochemical process of electron excitation by photon absorption, when the energy of the photon is too low to cause photoionization. The absorption of the photon takes place in accordance with Planck's quantum theory.
Photoexcitation plays a role in photoisomerization and is exploited in different techniques:
Dye-sensitized solar cells makes use of photoexcitation by exploiting it in cheaper inexpensive mass production solar cells.[2] The solar cells rely on a large surface area in order to catch and absorb as many high energy photons as possible. Shorter wavelengths are more efficient for the energy conversion compared to longer wavelengths, since shorter wavelengths carry photons that are more energy rich. Light containing shorter wavelengths therefore cause a longer and less efficient conversion of energy in dye-sensitized solar cells.
Photochemistry
Luminescence
Optically pumped lasers use photoexcitation in a way that the excited atoms in the lasers get an enormous direct-gap gain needed for the lasers.[3] The density that is needed for the population inversion in the compound Ge, a material often used in lasers, must become 1020 cm−3, and this is acquired via photoexcitation. The photoexcitation causes the electrons in atoms to go to an excited state. The moment the amount of atoms in the excited state is higher than the amount in the normal ground state, the population inversion occurs. The inversion, like the one caused with germanium, makes it possible for materials to act as lasers.
Photochromic applications. Photochromism causes a transformation of two forms of a molecule by absorbing a photon.[4] For example, the BIPS molecule(2H-l-benzopyran-2,2-indolines) can convert from trans to cis and back by absorbing a photon. The different forms are associated with different absorption bands. In a cis-form of BIPS, the transient absorption band has a value of 21050 cm−1, in contrast to the band from the trans-form, that has a value of 16950 cm−1. The results were optically visible, where the BIPS in gels turned from a colorless appearance to a brown or pink color after repeatedly being exposed to a high energy UV pump beam. High energy photons cause a transformation in the BIPS molecule making the molecule change its structure.
On the nuclear scale photoexcitation includes the production of nucleon and delta baryon resonances in nuclei.
^Pelc, J. S.; Ma, L.; Phillips, C. R.; Zhang, Q.; Langrock, C.; Slattery, O.; Tang, X.; Fejer, M. M. (2011-10-17). "Long-wavelength-pumped upconversion single-photon detector at 1550 nm: performance and noise analysis". Optics Express. 19 (22): 21445–56. Bibcode:2011OExpr..1921445P. doi:10.1364/oe.19.021445. ISSN 1094-4087. PMID 22108994. S2CID 33169614.
Photoexcitation is the production of an excited state of a quantum system by photon absorption. The excited state originates from the interaction between...
of many forms of luminescence (light emission) and is initiated by photoexcitation (i.e. photons that excite electrons to a higher energy level in an...
chemistry, photoisomerization is a form of isomerization induced by photoexcitation. Both reversible and irreversible photoisomerizations are known for...
of an electron to a higher energy state. This can either be done by photoexcitation (PE), where the original electron absorbs the photon and gains all...
phenomenon associated with electromagnetic radiation. It is produced by the photoexcitation of material, resulting in the production of thermal energy (heat)....
or do not exist in thermal equilibrium, but can be induced e.g. by photoexcitation. Chain-melted state: Metals, such as potassium, at high temperature...
are either injected from appropriate electrodes, upon doping or by photoexcitation. In molecular crystals the energetic separation between the top of...
such as ZnO, GaN and InN. Three-way coupling among piezoelectricity, photoexcitation and semiconductor is the basis of piezotronics (piezoelectricity-semiconductor...
oxidation or reduction, thereby initiating a redox pathway via tunable photoexcitation. Complexes containing high atomic number d6 metal centers, such as...
π-systems, which lowers the energy of HOMO and LUMO orbitals to promote photoexcitation. While many photosensitizers are organic or organometallic compounds...
9-kDa protein called PsaC that binds to the PsaA/PsaB core near FX. Photoexcitation of the pigment molecules in the antenna complex induces electron and...
electron to a more energetic, but still bound state. This can be done by photoexcitation (PE), where the electron absorbs a photon and gains all its energy...
elaborate one-step model treats the effect as a coherent process of photoexcitation into the final state of a finite crystal for which the wave function...
generated. Closely related to atomic recoil are electron recoil (see photoexcitation and photoionization) and nuclear recoil, in which momentum transfers...
this equation is the energy of the UV light quanta that are used for photoexcitation. Photoemission spectra are also measured using tunable synchrotron...
energy and converts it to chemical energy Beta-carotene Quench excess photoexcitation energy Heme B559 Bound to Cytochrome b559 (PsbE–PsbF) as a secondary/protective...
be destructive, as illustrated by the photodegradation of plastics. Photoexcitation is the first step in a photochemical process where the reactant is...
source other than force itself, ML is often manifested by external photoexcitation such as a UV lamp. The most common cause of ML is related to changes...
Radiative and Nonradiative Processes in Nanocrystalline ZnO Particles upon Photoexcitation". The Journal of Physical Chemistry B. 104 (8): 1715–1723. doi:10.1021/jp993327z...
Photochemical reduction involves chemical reduction (redox) generated from the photoexcitation of another molecule, called a photosensitizer. To harness the sun's...
Andreas W.; Ernst, Wolfgang E.; Koch, Markus (2018-10-01). "Femtosecond photoexcitation dynamics inside a quantum solvent". Nature Communications. 9 (1): 4006...
iodine atom at the shorter end of the triiodide anion dissociates upon photoexcitation showing two-body dissociation. In the solid state, the triiodide photochemistry...
(extinction coefficient of 40 M−1·cm−1) giving it a pale yellow color. Photoexcitation results in nearly quantitative formation of its triplet state through...
the introductory paragraph. A few further examples are given in ref. Photoexcitation has been shown to produce persistent states in vanadates and manganite...
as ZnO, GaN and InN. the three-way coupling among piezoelectricity, photoexcitation and semiconductor properties, which is the basis of piezotronics...
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