Taking Aim at Electrons: An Atomic-Scale Shooting Gallery
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From left: Uppsala University’s Melanie Mucke, Uppsala Professor Raimund Feifel and John Eland, a professor in the Physical and Theoretical Chemistry Laboratory at Oxford University and a guest… (Photo by Matt Beardsley) view »
In experiments resembling an atomic-scale shooting gallery, researchers are pioneering a new method for chemical analysis by zapping the innermost electrons out of atoms with powerful X-ray laser pulses from SLAC’s Linac Coherent Light Source (LCLS).
The technique, developed by an international research team and reported in the April edition of Physical Review Letters, allows chemical analysis with atomic resolution, taking spectroscopy - used to study the interaction of light and matter - to a new extreme.
“This is a powerful method to investigate complex molecules with which one aims at determining the arrangement of electrons and the geometrical structure of many systems, including biomolecules,” said Peter Salén, a Stockholm University physicist who participated in the research.
For example, it could be used to study the fundamental properties of molecules that encode the information in DNA and RNA, Salén said - which are of scientific interest when present in a DNA sequence and as individual molecules.
Much as planets orbit the sun, electrons orbit the nucleus of an atom at different distances, called shells.
When light from a high-energy X-ray laser hits an atom, it disrupts this arrangement, ejecting electrons from an inner shell. This creates “core holes,” vacant spaces that other orbiting electrons drop in to fill, usually within millionths of a billionth of a second. If the laser pulse is intense enough, it can eject other electrons, eventually depleting all of the inner shell electrons and creating a so-called “hollow” state.