Lining up for Photos

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Science  19 Jun 2009:
Vol. 324, Issue 5934, pp. 1493
DOI: 10.1126/science.324_1493d

Transient diffraction techniques can be used in the gas phase to probe molecules in the midst of transformation, but structural information is limited by the random orientation of the sample. In contrast, static diffraction techniques applied to crystals that keep the constituent molecules well aligned can provide exquisite three-dimensional structures. Reckenthaeler et al. show that ultrafast optical methods can begin to bridge these two limiting cases. The authors use femtosecond laser pulses to dissociate gas phase diiodotetrafluoroethane molecules, creating a C2F4I ensemble briefly aligned on account of the laser polarization. Before the alignment is lost, a short pulse of electrons is fired through the sample, allowing the determination of transient molecular structure. Because the alignment persists for several picoseconds, the method may offer the opportunity to study a range of more complex molecular structures and dynamics.

Phys. Rev. Lett. 102, 213001 (2009).

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