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  • Capturing roaming molecular...
    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

    Science (American Association for the Advancement of Science), 11/2020, Letnik: 370, Številka: 6520
    Journal Article

    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.