Electronic Transitions
Electronic Transitions - Related Videos
01:16
UV–Vis Spectroscopy: Molecular Electronic Transitions
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2024
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 process,...
02:58
Properties of Transition Metals
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2020
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals. Figure 1: Periodic Table. The transition metals are located in groups 3–11 of the periodic table. The inner transition metals are in the two rows...
02:31
Phase Transitions
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2020
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to occupy...
01:58
Cooperative Allosteric Transitions
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2020
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
08:19
Patterning via Optical Saturable Transitions - Fabrication and Characterization
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Cited by 1 •
2014
We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.
FAQs
The decisive condition is energy matching: an absorbed photon can promote an electron only when its energy corresponds to the gap between a lower-energy level and an available higher level. Because those levels are quantized, different substances support different transition energies. This matching principle explains why absorption patterns can serve as signatures of electronic structure.
Orbital identity influences the transition and the resulting spectrum. Molecular orbitals may be bonding, nonbonding, or antibonding, so moving an electron between different orbital types produces characteristic absorption or emission patterns. Examining those patterns helps chemists relate observed spectral behavior to how electrons are arranged within a molecule, rather than treating all transitions as equivalent.
Relaxation determines how absorbed energy appears after excitation. An excited electron may return toward a lower-energy arrangement while releasing energy as light or heat. Light-producing relaxation contributes to emission observations, whereas heat-producing relaxation does not create the same optical signal. This distinction helps explain why a substance can absorb energy yet show different emission behavior.
Chemists investigate them by examining absorption and emission patterns with UV-visible and fluorescence spectroscopy. The measured patterns provide evidence about electronic structure and can reveal how a substance responds after absorbing energy. Comparing these characteristic signals supports identification and analysis, while repeated measurements can also help follow changes in a chemical system.
These measurements can help identify substances and analyze their electronic structure through characteristic spectral patterns. They also show how absorbed energy is associated with subsequent light emission or other relaxation behavior. In chemistry, that information connects an observed spectrum with molecular electron arrangements, helping explain properties such as molecular color and photochemical behavior.
A reaction can be monitored by tracking changes in its characteristic absorption or emission patterns over time. Because these patterns reflect electronic structure, changes in the signals can indicate that the substances or their electron arrangements are changing. This application extends spectroscopy beyond identification, allowing chemists to analyze reaction progress through measurable electronic behavior.