Related Experiment Video
Updated: May 26, 2025

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Carotenoid radical formation after multi-photon excitation of 8'-apo-β-carotenal
Václav Šebelík1, Valentyna Kuznetsova1, Ivana Šímová1
1Department of Physics, Faculty of Science, University of South Bohemia, Czech Republic. tpolivka@prf.jcu.cz.
Abstract:
Carotenoids containing a conjugated CO group exhibit complex excited-state dynamics that are influenced by solvent polarity due to the involvement of an intramolecular charge transfer (ICT) state. Our study explores the excited-state behavior of 8'-apo-β-carotenal under multi-photon excitation conditions. Using near-infrared (1300 nm) multi-photon excitation, we observe the formation of a cation radical of 8'-apo-β-carotenal, a process distinct from those following one-photon visible or UV excitation. Our findings suggest that this radical formation results from multi-photon excitation involving a higher-lying dark state, supported by intensity-dependent experiments. This work demonstrates that radical generation is a characteristic of this higher excited state and is not produced during relaxation from the S1/ICT state. The results open new pathways for understanding carotenoid radical formation mechanisms under intense multi-photon excitation.
Related Concept Videos
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Radical Autoxidation
Radical Formation: Addition
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
Radical Formation: Elimination
Radical Reactivity: Overview
Radicals: Electronic Structure and Geometry
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...

