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  2. Population inversion - Wikipedia

    en.wikipedia.org/wiki/Population_inversion

    In physics, specifically statistical mechanics, a population inversion occurs when a system (such as a group of atoms or molecules) exists in a state in which more members of the system are in higher, excited states than in lower, unexcited energy states. It is called an "inversion" because in many familiar and commonly encountered physical ...

  3. Ring flip - Wikipedia

    en.wikipedia.org/wiki/Ring_flip

    In organic chemistry, a ring flip (also known as a ring inversion or ring reversal) is the interconversion of cyclic conformers that have equivalent ring shapes (e.g., from a chair conformer to another chair conformer) that results in the exchange of nonequivalent substituent positions. [1]

  4. Chiral inversion - Wikipedia

    en.wikipedia.org/wiki/Chiral_inversion

    Chiral inversion is the process of conversion of one enantiomer of a chiral molecule to its mirror-image version with no other change in the molecule. [1] [2] [3] [4]Chiral inversion happens depending on various factors (viz. biological-, solvent-, light-, temperature- induced, etc.) and the energy barrier energy barrier associated with the stereogenic element present in the chiral molecule. 2 ...

  5. Molecular symmetry - Wikipedia

    en.wikipedia.org/wiki/Molecular_symmetry

    An inversion center is a special case of having a rotation-reflection axis about an angle of 180° through the center. Examples are xenon tetrafluoride (a square planar molecule), where the inversion center is at the Xe atom, and benzene (C 6 H 6) where the inversion center is at the center of the ring.

  6. Inversion - Wikipedia

    en.wikipedia.org/wiki/Inversion

    Nitrogen inversion, a chemical process in which a trigonal nitrogen-containing structure turns inside-out; Population inversion, in statistical mechanics, when a system exists in state with more members in an excited state than in lower-energy states; Pyramidal inversion, a chemical process in which a trigonal structure turns inside-out

  7. Pyramidal inversion - Wikipedia

    en.wikipedia.org/wiki/Pyramidal_inversion

    Pyramidal inversion in nitrogen and amines is known as nitrogen inversion. [8] It is a rapid oscillation of the nitrogen atom and substituents, the nitrogen "moving" through the plane formed by the substituents (although the substituents also move - in the other direction); [ 9 ] the molecule passing through a planar transition state . [ 10 ]

  8. Degenerate energy levels - Wikipedia

    en.wikipedia.org/wiki/Degenerate_energy_levels

    In quantum mechanics, an energy level is degenerate if it corresponds to two or more different measurable states of a quantum system.Conversely, two or more different states of a quantum mechanical system are said to be degenerate if they give the same value of energy upon measurement.

  9. Concerted reaction - Wikipedia

    en.wikipedia.org/wiki/Concerted_reaction

    S N 2 reaction of a bromide ion with chloroethane showing the concerted nature of the reaction, the transition state and the predictable stereochemistry through Walden inversion. In chemistry, a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step.