Elementary Particles Star in New 'Dance Movie'

[n2doc]

ScienceDaily (Aug. 16, 2010) — Scientists of the Max-Born-Institute in Berlin (Germany) have directly measured the spatial positions of electrons and protons during a chemical reaction using ultrashort X-ray flashes.

A chemical reaction generates new compounds out of one or more initial species. On a molecular level, the spatial arrangement of electrons and nuclei changes. While the structure of the initial and the product molecules can be measured routinely, the transient structures and molecular motions during a reaction have remained unknown in most cases. This knowledge, however, is a key element for the exact understanding of the reaction.


Crystal structure of ammonium sulfate (yellow: sulphur, red: oxygen, blue: nitrogen and grey: hydrogen). The protons along the dotted line leave their ammonium ions and merge with an electron stemming from sulfur atoms to a new hydrogen atom which subsequently jumps back and forth between two spatial positions. This dance takes place in a plane shown on the right hand side. This plane goes through the dotted line and stands perpendicular to the paper in the subfigure on the left hand side. (Credit: Image courtesy of Forschungsverbund Berlin e.V. (FVB))


The ultimate dream is a "reaction microscope" which allows for an in situ imaging of the molecules during a reaction. The technological challenges of such an ultrafast "cinema" were mastered only recently. Using ultrashort X-ray pulses, researchers at the Max-Born-Institute in Berlin, Germany, have now made a "molecular movie" of a chemical reaction with a resolution on atomic length (10‑10 meters) and time scales (10‑13 seconds).


Michael Woerner, Flavio Zamponi, Zunaira Ansari, Jens Dreyer, Benjamin Freyer, Mirabelle Premont-Schwarz und Thomas Elsaesser report on a direct time-resolved observation of a chemical reaction in ammonium sulfate crystals <(NH4)2SO4> in the most recent issue of The Journal of Chemical Physics.

more

http://www.sciencedaily.com/releases/2010/08/100817143814.htm