Related Experiment Video
Updated: Nov 24, 2025
08:04
Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
8.8K
Disintegration of excitons in π-conjugated molecules
1State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China. shengw@fudan.edu.cn.
Physical Chemistry Chemical Physics : PCCP
|December 23, 2020
Summary
Excitons do not form in π-conjugated molecules under the Rytova-Keldysh potential. The Pariser-Parr-Pople model shows excitons may survive with weak screening, but the optical gap remains insensitive to the dielectric environment.
Area of Science:
- Quantum chemistry
- Materials science
- Condensed matter physics
Background:
- Exciton formation in π-conjugated systems is crucial for understanding their optical properties.
- The influence of electron-electron interactions and dielectric environment on excitons is a key research area.
Purpose of the Study:
- To investigate exciton formation in anthracene, phenanthrene, and pyrene using different theoretical models.
- To determine the impact of electron-electron interaction potentials and dielectric screening on molecular optical gaps.
Main Methods:
- Exact diagonalization (ED) method to study electron-electron interactions.
- Pariser-Parr-Pople (PPP) model to simulate exciton behavior under varying screening conditions.
Main Results:
- Excitons were found to be unable to form in anthracene, phenanthrene, and pyrene when using the Rytova-Keldysh (RK) potential.
- Within the Pariser-Parr-Pople (PPP) model, excitons could persist only under weak screening.
- The optical gap demonstrated insensitivity to the dielectric environment due to opposing contributions from excitonic effects and quasiparticle corrections.
Conclusions:
- The formation and stability of excitons in π-conjugated molecules are highly dependent on the chosen theoretical model for electron-electron interactions.
- The optical gap's insensitivity to the dielectric environment suggests a complex interplay between electronic correlation and screening effects in these systems.
More Related Videos
Related Concept Videos
01:25Deactivation Processes: Jablonski Diagram
1.3K
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...
1.3K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
2.0K
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
Selection Rules: Photochemical Activation
2.0K
01:32UV–Vis Spectroscopy of Conjugated Systems
7.9K
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in...
One of the factors influencing λmax is the extent of conjugation in...
7.9K
01:24π Molecular Orbitals of 1,3-Butadiene
10.7K
Conjugated dienes have lower heats of hydrogenation than cumulated and isolated dienes, making them more stable. The enhanced stabilization of conjugated systems can be understood from their π molecular orbitals.
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
10.7K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.7K
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.
2.7K
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
2.3K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
2.3K