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Related Concept Videos

Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement01:21

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement

The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Thermal Sigmatropic Reactions: Overview01:16

Thermal Sigmatropic Reactions: Overview

Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in 1,5-hexadiene, referred to as...
Photoelectric Effect02:26

Photoelectric Effect

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Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...

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Related Experiment Video

Updated: Jun 15, 2026

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
06:53

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−

Published on: July 27, 2018

Rearrangement effects in photoionization.

M Y Amusia

    Applied Optics
    |March 18, 2010
    PubMed
    Summary

    This study explores the random phase approximation with exchange (RPAE) method, discussing its limitations and proposing a more general theory. It examines electron shell rearrangements and vacancy decay effects in atomic ionization.

    Area of Science:

    • Atomic Physics
    • Quantum Mechanics
    • Theoretical Chemistry

    Background:

    • The random phase approximation with exchange (RPAE) is a theoretical method used in atomic physics.
    • Understanding electron behavior in atoms is crucial for various scientific fields.
    • Previous models have limitations in accurately describing complex atomic processes.

    Purpose of the Study:

    • To discuss recent developments and physical backgrounds of the RPAE method.
    • To identify the limitations of the RPAE method.
    • To propose a more general theory overcoming RPAE difficulties.

    Main Methods:

    • Discussion of RPAE method's theoretical underpinnings.
    • Analysis of RPAE limitations.
    • Consideration of generalized theories incorporating electron shell rearrangement and vacancy decay.

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    Last Updated: Jun 15, 2026

    Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
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    Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−

    Published on: July 27, 2018

    Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
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    Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch

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    08:51

    Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

    Published on: August 18, 2017

  • Examination of two-electron-two-hole virtual excitations.

    • Main Results:

    • Identified limitations of the RPAE method.
    • Proposed generalizations to RPAE to account for ionization dynamics.
    • Highlighted the significance of electron shell rearrangement and vacancy decay.
    • Investigated the role of two-electron-two-hole virtual excitations.

    Conclusions:

    • The RPAE method has inherent limitations that necessitate more advanced theoretical approaches.
    • Generalized theories can better describe atomic ionization by including electron shell dynamics and decay processes.
    • Further research into electron density oscillations in atoms is warranted.