Capturing roaming molecular fragments in real time

Since the discovery of roaming as an alternative molecular dissociation pathway in formaldehyde (H CO), it has been indirectly observed in numerous molecules. The phenomenon describes a frustrated dissociation with fragments roaming at relatively large interatomic distances rather than following con...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2020-11, Vol.370 (6520), p.1072-1077
Main Authors: Endo, Tomoyuki, Neville, Simon P, Wanie, Vincent, Beaulieu, Samuel, Qu, Chen, Deschamps, Jude, Lassonde, Philippe, Schmidt, Bruno E, Fujise, Hikaru, Fushitani, Mizuho, Hishikawa, Akiyoshi, Houston, Paul L, Bowman, Joel M, Schuurman, Michael S, Légaré, François, Ibrahim, Heide
Format: Article
Language:English
Subjects:
Deuteration
First principles
Formaldehyde
Fragments
Radicals
Real time
Stochasticity
Time
Trajectory analysis
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Summary:Since the discovery of roaming as an alternative molecular dissociation pathway in formaldehyde (H CO), it has been indirectly observed in numerous molecules. The phenomenon describes a frustrated dissociation with fragments roaming at relatively large interatomic distances rather than following conventional transition-state dissociation; incipient radicals from the parent molecule self-react to form molecular products. Roaming has been identified spectroscopically through static product channel-resolved measurements, but not in real-time observations of the roaming fragment itself. Using time-resolved Coulomb explosion imaging (CEI), we directly imaged individual "roamers" on ultrafast time scales in the prototypical formaldehyde dissociation reaction. Using high-level first-principles simulations of all critical experimental steps, distinctive roaming signatures were identified. These were rendered observable by extracting rare stochastic events out of an overwhelming background using the highly sensitive CEI method.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.abc2960