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An international team of physicists led by Ursula Keller at the Institute for Quantum Electronics of the ETH Zurich has now added a new dimension to the experimental investigation of this important effect. Using attosecond laser pulses they were able to measure a tiny time difference in the ejection of the electron from a molecule depending on the position of the electron inside the molecule.
"For quite some time, people have studied the time evolution of the photoelectric effect in atoms," says PhD student Jannie Vos, "but very little has so far been published on molecules."
Fact - Molecules - Atoms - Atom - Outermost
That is mainly due to the fact that molecules are considerably more complex than single atoms. In an atom, the outermost electron moving around the atomic nucleus is essentially catapulted out of its orbit. In a molecule, by contrast, two or more nuclei share the same electron. Where it is located depends on the interplay between the different attractive potentials. Exactly how the photoelectric effect happens under such conditions could only now be studied in detail.
To do so, Keller and her co-workers used carbon monoxide molecules, which consist of two atoms -- one carbon and one oxygen atom. Those molecules were exposed to an extreme ultraviolet laser pulse that only lasted for a few attoseconds. (An attosecond is the billionth part of a billionth of a second). The energy of the ultraviolet photons ripped an electron out of the molecules, which subsequently broke up into their constituent atoms. One of those atoms turned into a positively charged ion in the process.
Instrument - Researchers - Directions - Electrons - Ions
Using a special instrument, the researchers then measured the directions in which the electrons and ions flew away. A second laser pulse,...
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