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 | Assistant Professor
513 McMillen Laboratories Department of Chemistry
Washington University in St. Louis
St. Louis, MO 63130-4899 Phone: 314 935 5928 |
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Postdoctoral Research Associate, University of Arizona (2002-5)
Ph.D. 1995 University of Nottingham, UK
B.Sc. 1990 University of Nottingham, UK
| Research Our research program is directed towards the elucidation of the molecular level dynamics occurring in reactive processes, specifically those occurring in anionic systems.
Our approach is to initiate a reaction in a precursor anionic species through laser excitation. The evolution of the electronic eigenvalues and eigenfunctions of the system is followed in real time using a probe laser pulse (arriving at a well defined delay susequent to the initiating pulse) via photodetachment imaging.
Photodetachment Imaging
Photodetachment imaging represents an extension of photoelectron spectroscopy. Electrons are removed from an anionic species via laser excitation, leaving the neutral species behind. A 2D projection (image) of the initial 3D distribution in momentum space is obtained using a position sensitive detector. The original 3D photoelectron velocity distribution can be mathematically extracted (reconstruction). We retrieve the photoelectron spectrum (which allows determination of the electronic eigenvalues of the system) and the angular distribution of the electrons (which is related to the electron wavefunction prior to detachment).
Time Resolved Photodissociation
An ultrafast laser pulse (the pump) is used to excite an anionic species to a dissociative electronic state. A second ultrafast laser pulse (delayed by 10's - 100's of fs with respect to the pump pulse) is used to photodetach the excess electron. Such experiments reveal the dynamics of a reaction in great detail. Features of the excited anionic and terminal neutral potential surfaces are revealed through examination of the photoelectron spectra. Furthermore, the changing angular distributions track the evolution of the electronic wavefunctions from those of reactants into those of products.
Low Energy Electron Transfer Induced Reaction Dynamics
We are particularly interested in low energy electron transfer induced processes. These are important in many areas, including plasma remediation technologies, the chemistry of the ionosphere and biological tissue damage due to ionizing radiation.
A cluster containing an anionic moiety (such as Cl-) and neutral species of interest (e.g. uracil) is prepared. The anionic moiety has two functions in these experiments. It allows the selection (by mass) of particular clusters and hence particular neutral assemblies of molecules (we can selectively add molecules to the cluster). Secondly, it acts as an in situ electron source. The pump laser pulse is used to transfer the electron from the anionic moiety to the neutral part of the cluster at a well defined instant in time and with good control over the energetics of the electron-neutral collision. The progress of the reaction can be followed via photodetachment imaging, using the probe pulse to detach the electron from the transient (and product) anionic species produced as a function of time.
| Selected Publications
- R.Mabbs, K. Pichugin, A. Sanov, 'Dynamic Molecular Interferometer: Probe of Inversion Symmetry in I2- Photodissociation,’ J. Chem. Phys. 123, 054329 (2005).
- R. Mabbs, K. Pichugin and A. Sanov, 'Time-resolved imaging of the reaction coordinate,' J. Chem. Phys. 122, 174305 (2005). [Reprinted as selected article in Virtual Journal of Ultrafast Science, Vol. 4(6), 2005]
- R. Mabbs, E. Surber and A. Sanov, 'Solvation Effects on Photoelectron Anisotropy and Photodetachment Cross Section,'
J. Chem. Phys. 122, 054308, (2005).
- R. Mabbs, K. Pichugin, E. Surber and A. Sanov, 'Time Resolved electron detachment imaging of the I- channel in I2Br- photodissociation,'
J. Chem. Phys. 121, 265-272, (2004).
[Reprinted as selected article in Virtual Journal of Ultrafast Science, Vol. 3(7), 2004]
- R. Mabbs, E. Surber, L. Velarde and A. Sanov, 'Effects of solvation and core switching on the photoelectron angular distributions from (CO2)n- and (CO2)n-·H2O,'
J. Chem. Phys. 120, 5148-5154, (2004).
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Page Last Updated: October 12th, 2005
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