Related Experiment Video
Updated: Sep 26, 2026

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Photostimulated desorption and ortho-para conversion of H2 on Ag surfaces
K Fukutani1, K Yoshida, M Wilde
1Institute of Industrial Science, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Abstract:
Photostimulated desorption and change of the ortho-para ratio of H2 physisorbed on Ag at 7 K are reported. After pump laser excitation at 193 nm neutral H2 desorbing in a nonthermal process is state selectively detected by resonance-enhanced multiphoton ionization. At weak pump laser fluence the natural ortho-para conversion of H2 on Ag was monitored to proceed with a conversion time of approximately 780 s, which is in good agreement with predictions based on an electron-exchange-hyperfine-contact model. With increasing pump laser fluence, the ortho-para ratio decreases faster, suggesting photoassisted ortho-para H2 conversion.
Related Concept Videos
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Cycloaddition Reactions: MO Requirements for Photochemical Activation
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Thermal and Photochemical Electrocyclic Reactions: Overview

