Düsseldorf 2007 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 27: Kalte Moleküle II (gemeinsam mit MO)
Q 27.1: Hauptvortrag
Dienstag, 20. März 2007, 14:00–14:30, 6B
Manipulating large molecules: selecting isomers, orienting, and slowing polar molecules with strong electric fields — •Jochen Küpper — Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin
Polar molecules can be manipulated using strong electric fields. Small molecules, for example OH or NH3, have been focused and state selected by electrostatic multipole guides, they have been slowed in Stark decelerators and stored in rings or traps. Practically all these experiments have been performed on molecules in low-field-seeking quantum states. For larger molecules, however, all states are high-field seeking at the relevant electric field strengths.
To manipulate the motion of large molecules one has to use Alternate Gradient (dynamic) focusing. In prototype experiments small molecules in high-field seeking states have been decelerated [1]. We are extending these methods to the focusing and deceleration of large molecules. For large (bio-)molecules typically a number of different conformers (structural isomers) are present in a supersonic jet. Using switched electric fields in a “quadrupole” guide such conformers can spatially be separated due to their different mass-to-dipole (m/µ) ratios, similar to a quadrupole mass-to-charge (m/q) filter for ions. Moreover, the molecular packets transmitted through the guide are very well suited for brute-force orientation.
We have also set up a modular Alternate Gradient deceleration experiment, which allows us to slow polar molecules in low- and high-field seeking states. We have successfully decelerated several molecules, for example benzonitrile (C7H5N), in different quantum states.
I will discuss the prospects for novel studies on such molecular systems that these experiments on the structural and spatial separation and the deceleration of large molecules offer. For example, oriented samples of individual conformers of large molecules will greatly benefit scattering experiments for direct structure determination.
[1] H. L. Bethlem, M. Tarbutt, J. Küpper, D. Carty, K. Wohlfart, E. Hinds, and G. Meijer, J. Phys. B 39, R263 (2006)
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