Reactions with Rydberg Atoms

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 interesting discoveries.

See E. Wrede et al., Phys. Chem. Chem. Phys. 7 (2005), 1577 and its experimental walk through.

Equipment

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): 1–78 APR 2004.

C. Vallance, 'Molecular photography': velocity-map imaging of chemical events.
Philosophical Transactions of the Royal Society A 362(1825): 2591–2609 DEC 2004.

Links

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Bristol Laser Group Ion Imaging page.

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