Reactive Scattering of Rydberg Atoms (funded by EPSRC)
The reactive scattering of a Rydberg atom, A*, with a molecule
(A* + BC ® AB + C*) is a new and interesting
variation of a bimolecular reaction. By choosing the Rydberg state of the colliding
atom one can change the character of the
scattering between the usually studied 'extremes' of a neutral reaction with
the collision partners in their ground electronic states (A + BC) and its ionic
counterparts (e.g. A+ + BC). A highly excited Rydberg electron orbits around
the ion core at great distance and slowly compared to the motion of the colliding
nuclei. Thus, the Rydberg electron can be viewed as a spectator while the ionic
reaction takes place.
The aim of this project is to study this kind of reactions as a function of
Rydberg state, i.e. to control the size of the orbit of the Rydberg electron
and therefore the (otherwise infinite) range of the Coulomb force of the ion.
Open and very interesting questions are: How does the reaction depend on the
Rydberg state of the atom? Does the Rydberg state change during the reaction?
This is an entirely new field of scattering dynamics with the potential of many
See E. Wrede et al., Phys. Chem. Chem. Phys. 7 (2005), 1577
and its experimental walk through.
We are currently setting-up the new experiment. The vacuum chamber incorporates
two supersonic molecular beams sources, a special time-of-flight mass spectrometer
for ion imaging and a 2-dimensional detector with CCD camera. Central for all
the experiments is the laser system consisting of three Nd:YAG pumped dye lasers that is
used to prepare and detect the different species using various laser spectroscopic
techniques, e.g. multi photon ionisation and Rydberg atom tagging.
The experimental set-up consists of a vacuum chamber (above) and three pulsed dye laser systems.
Recent general references on Rydberg atoms/molecules and ion imaging as detection technique
T.P. Softley, Applications of molecular Rydberg states in chemical dynamics and spectroscopy.
International Reviews in Physical Chemistry 23(1): 178 APR 2004.
C. Vallance, 'Molecular photography': velocity-map imaging of chemical events.
Philosophical Transactions of the Royal Society A 362(1825): 25912609 DEC 2004.
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