HOMO and LUMO are acronyms for highest occupied molecular orbital and lowest unoccupied molecular orbital, respectively. Acronyms, initialisms, and alphabetisms are Abbreviations that are formed using the initial components in a phrase or name In Chemistry, a molecular orbital (or MO) is a region in which an Electron may be found in a Molecule. In Chemistry, a molecular orbital (or MO) is a region in which an Electron may be found in a Molecule. The difference of the energies of the HOMO and LUMO, termed the band gap, can sometimes serve as a measure of the excitability of the molecule: the smaller the energy, the more easily it will be excited. Excitation is an elevation in energy level above an arbitrary baseline energy state In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός
The HOMO level is to organic semiconductors and quantum dots what the valence band is to inorganic semiconductors. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that A quantum dot is a Semiconductor whose Excitons are confined in all three Spatial dimensions. In Solids the valence band is the highest range of Electron energies where electrons are normally present at Absolute zero. The same analogy exists between the LUMO level and the conduction band. In the Physics field of Semiconductors and insulators the conduction band is the range of Electron Energy, higher than that of the The energy difference between the HOMO and LUMO level is regarded as band gap energy. In Solid state physics and related applied fields a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states
When the molecule forms a dimer or an aggregate, the proximity of the orbitals of the different molecules induce a splitting of the HOMO and LUMO energy levels. A dimer is a Chemical or Biological entity consisting of two subunits called Monomers which are held together by either Intramolecular forces This splitting produces vibrational sublevels which each have their own energy, slightly different from one another. There are as many vibrational sublevels as there are molecules that interact together. When there are enough molecules influencing each other (e. g. in an aggregate), there are so many sublevels that we no longer perceive their discrete nature: they form a continuum. We no longer consider energy levels, but energy bands.
See also
- Diels-Alder reaction
- Electron configuration
- Koopmans' theorem
- Ligand
- Molecular orbital
- Organic semiconductor
Bibliography
- Martin Pope et Charles E. The Diels-Alder reaction is an Organic chemical reaction (specifically a Cycloaddition) between a conjugated Diene and a substituted Alkene, In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other Koopmans' theorem is an approximation in Molecular orbital theory, such as Density functional theory, or Hartree-Fock theory in which the first Ionization In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally In Chemistry, a molecular orbital (or MO) is a region in which an Electron may be found in a Molecule. An organic semiconductor is any Organic material that has Semiconductor properties Martin Pope (b August 22, 1918) is a physical chemist and Professor emeritus at New York University. Swenberg, Electronic Processes in Organic Crystals and Polymers, 2nd ed. , Oxford Science Publications, Oxford University Press, New York, 1999
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