Mid Term Review

Surprising Spectroscopic Signals of Isomerization

Date & time

Thu 1 Dec 2016, 2–3pm



RSPE Seminar Room


Members of RSPE welcome


Mr Benjamin Laws
Laser Physics Centre / RSPE

Vinylidene (CCH2), is an important reactive intermediate in a variety of chemical processes. It readily undergoes isomerization to form linear acetylene (HCCH), in a process which serves as a prototype for hydrogen shift reactions widely seen in organic chemistry. In this work, the isomerization barrier is studied using the technique of velocity-map imaging of photoelectrons detached from the vinylidene anion. Recent results have discovered not previously seen anomalous electron distributions, which surprisingly only occur for a few special transitions. I will discuss how these anomalous transitions may be the key to finally solving a 30 year old problem surrounding the mechanism of vinylidene isomerization.

Production of vinylidene ions is a difficult task, with various schemes and chemistries tested. One such scheme, involving N2O, also produced a large NO2 anion signal. Measurement of this ion signal revealed a lot of surprising additional electron structure, occurring at high kinetic energies. These additional fast electrons, turn out to be associated with the highly reactive NOO peroxy radical, an isomer of the common ONO radical, that has previously only been postulated to exist. This research provides the first experimental measurement of NOO, a discovery that has many potential implications for atmospheric chemical science.

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