EGAS41 - Swansea University

41 st EGAS PR 6 Gdańsk 2009
Chemical applications of laser- and sympathetically cooled ions
in ion traps
Stefan Willitsch
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
E-mail: stefan.willitsch@unibas.ch
The recent progress in the generation of translationally ”cold” atoms and molecules has
enabled to study physical and chemical processes in a new regime. A particular intriguing
perspective is the investigation of reactive molecular scattering processes at ultralow collision
energies to characterise quantum-mechanical effects which dominate the chemical
reactivity at very low temperatures. However, such studies have thus far been prevented
by the difficulties to detect and analyse the small number of scattering events per experimental
cycle limited by the low number densities of cold molecules that can be produced
with present-day sources.
We have recently developed a novel experimental setup to study reactive collisions
between translationally cold ions and neutral molecules which overcomes these difficulties
[1,2]. Our new experiment consists of a linear Paul trap for the laser- and sympathetic
cooling of atomic and molecular ions combined with a quadrupole-guide velocity selector
for the generation of translationally cold neutrals [3]. The high detection sensitivity which
can be achieved using Coulomb-crystallised ions allows us to study cold ion-molecule
reactive collisions on the single-particle level. In the presentation we review recent results
on selected cold ion-molecule reactions, discuss the experimental parameters influencing
the collision energy and chemical reactivity and explore further developments towards
fully quantum-state selected experiments at even lower energies.
References
[1] S. Willitsch, M. Bell, A. Gingell, S.R. Procter, T.P. Softley, Phys. Rev. Lett. 100,
043203 (2008)
[2] S. Willitsch, M. Bell, A. Gingell, T.P. Softley, Phys. Chem. Chem. Phys., 10, 7200
(2008)
[3] S.A. Rangwala, T. Junglen, T. Rieger, P.W.H. Pinkse, G. Rempe, Phys. Rev. A 67,
043406 (2003)
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