Activation of Unimolecular Reactions by Ambient Blackbody Radiation
R. C. Dunbar,
*
T. B. McMahon
*
The historical "radiation hypothesis" as a mechanism for
activating unimolecular thermal dissociation of gas-phase molecules, long discredited on the authority of Langmuir, has been revitalized by
the discovery and characterization of the process of thermal dissociation of trapped gas-phase ions by the ambient blackbody radiation field surrounding the ions. This development was made possible by improvements in Fourier transform ion cyclotron
instrumentation that allowed long-time trapping of weakly bound cluster
ions at extremely low pressures. Binding energies can be derived from measurements of these dissociation rate constants both by detailed kinetic modeling and by simpler Arrhenius temperature-dependence approaches, although the latter require special considerations for
small molecules. These approaches have been applied to thermal dissociations of molecules, including cluster ions and large
biomolecule ions.
R. C. Dunbar is in the Department of Chemistry, Case Western
Reserve University, Cleveland, OH 44106, USA. E-mail: rcd{at}po.cwru.edu.
T. B. McMahon is in the Department of Chemistry, University of
Waterloo, Waterloo, Ontario N2L 3G1, Canada. E-mail:
mcmahon{at}watsci.uwaterloo.ca
*
To whom correspondence should be addressed.
