Phase Space Structures Explain Hydrogen Atom Roaming in Formaldehyde Decomposition

Frederic A L Mauguiere, Peter R C Collins, Zeb C. Kramer, Barry K. Carpenter, Gregory S. Ezra, Stavros Farantos, Stephen R Wiggins

Research output: Contribution to journalArticle (Academic Journal)peer-review

33 Citations (Scopus)
357 Downloads (Pure)


We re-examine the prototypical roaming reaction—hydrogen atom roaming in formaldehyde decomposition—from a phase space perspective. Specifically, we address the question “why do trajectories roam, rather than dissociate through the radical channel?” We describe and compute the phase space structures that define and control all possible reactive events for this reaction, as well as provide a dynamically exact description of the roaming region in phase space. Using these phase space constructs, we show that in the roaming region, there is an unstable periodic orbit whose stable and unstable manifolds define a conduit that both encompasses all roaming trajectories exiting the formaldehyde well and shepherds them toward the H2···CO well.
Original languageEnglish
Pages (from-to)4123−4128
Number of pages6
JournalJournal of Physical Chemistry Letters
Issue number20
Early online date1 Oct 2015
Publication statusPublished - 15 Oct 2015


  • formaldehyde
  • roaming reactions
  • transition state theory
  • NHIM
  • periodic orbits
  • phase space


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