The Weakness of HO₃

 The Earth's atmosphere as seen from the International Space Station. Credit: NASA/JPL/UCSD/JSC

OH radicals play a critical role in the chemistry of Earth's atmosphere. Understanding atmospheric reaction networks thus requires an accurate knowledge of OH sources and sinks. One vexing question has been whether or not a significant pool of OH binds temporarily with oxygen to form HO₃. A team from the IPR in collaboration with Professor Ian WM Smith from Cambridge have succeeded in measuring the equilibrium constant for this reaction using sensitive fluorescent tracking of OH in a low temperature supersonic flow (CRESU) apparatus. This measurement was then used to quantify the strength of the O₂–OH bond, which was found to be too weak for the complexation to play a major role in the atmosphere. The research was published as a report in the journal Science on June 4, 2010:

Science 4 June 2010: Vol. 328. no. 5983, pp. 1258 – 1262

DOI: 10.1126/science.1184459

The Thermodynamics of the Elusive HO₃ Radical

Sébastien D. Le Picard,^1,* Meryem Tizniti,¹ André Canosa,¹ Ian R. Sims,^1,* Ian W. M. Smith^2,*

1 Institut de Physique de Rennes, Equipe : "Astrochimie Expérimentale", UMR 6251 du CNRS, Bât. 11c – Université de Rennes 1, Campus de Beaulieu, 35042 RENNES Cedex, France.

2 The University Chemical Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K.

* To whom correspondence should be addressed. E-mail : sebastien.le-picard@univ-rennes1.fr; ian.sims@univ-rennes1.fr;  iwms2@cam.ac.uk