New technique enables specific orientation of molecules
The development of new x-ray free-electron lasers opens the perspective for following changes in molecular structures during a (bio) chemical reaction through x-ray diffraction. A requirement however is that all molecules have to face the same way at the start of the experiment.
With a new technique with which molecules are oriented using a combination of laser and continuous electrical fields, this is now possible. The article with the findings of the AMOLF researchers from the XUV Physics research group were published online on the 22nd of March in the prestigious journal Nature Physics. It will appear in print within several weeks.
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FOM press release (Dutch)
Reference:
Impulsive orientation and alignment of quantum-state-selected NO molecules
Omair Ghafur, Arnaud Rouzée, Arjan Gijsbertsen,Wing Kiu Siu, Steven Stolte and Marc J.J. Vrakking.
For more information:
Prof. Dr. Marc Vrakking
Figure 1. From isotrope molecules to oriented molecules. In a gas of molecules a preferred direction generally doesn’t exist for the orientation of the molecules. With laser techniques it is possible to create aligned molecules, which means that for all molecules, the internuclear axis is preferably aligned along a certain axis. It is even better to orient molecules, which means that the molecules also all point in the same direction.
Figure 2. The orientation experiment. In the AMOLF experiment NO-molecules first move through a hexapole structure, that enables the focusing of different rotational states at different distances. A specially designed laser pulse, existing of a long pulse with a low intensity followed by a short pulse with a higher intensity, in combination with a strong continuous electrical field, enables the orientation of the molecules. The orientation is measured through ionisation and dissociation of the molecules with a UV (ultraviolet) laser, and detection of charged fragments on an 'imaging detector'.