Atoms Can Transfer Their Internal "Stress" To Other Atoms

Atoms can transfer their internal "stress" to other atoms, new experiments have revealed. Compared to atoms that are all by themselves, atoms with a close neighbor have a very efficient and surprising way to get rid of excess internal energy. An excited atom can hand over its energy to a neighbor, a research team led by the University of Frankfurt has demonstrated experimentally in a measurement carried out at the Berlin synchrotron facility BESSY II (R. Doerner, doerner@hsb.uni-frankfurt.de).

Predicted in 1997 by a group at Heidelberg University (Cederbaum et al., Phys Rev. Lett, 15 Dec 1997), this decay mechanism occurs when atoms or molecules lump together. Once an excited particle is placed in an environment of other particles such as in clusters or fluids, the novel de-excitation mechanism, called "Interatomic Coulombic Decay," leads to the emission of very low-energy electrons from a particle that is neighboring the initially excited one (see figure at Physics News Graphics).

The researchers demonstrated the effect in a pair of weakly bound neon atoms. The two neon atoms were separated by 3.4 Angstroms (about 6 times the radius of the neon atom) and held together by a weak "van der Waals" bond. Removing a tightly bound electron from one of the neon atoms allowed one of the less tightly bound atoms to jump down to the tightly bound spot and in the process gained energy. The extra energy was not sufficient to liberate any of the remaining electrons in the same neon atom, but it was sufficient to release an electron in the neighboring atom.

This newly verified effect may have a wide-ranging impact in chemistry and biology since it is predicted to happen frequently in most hydrogen-bonded systems, most prominently liquid water. Furthermore, it may be an important, and so far unknown, source of low-energy electrons, which have recently been shown to cause damage to DNA (see Update 636). (Jahnke et al., Physical Review Letters, 15 October 2004; also see researchers' website at http://hsb.uni-frankfurt.de/photoncluster/ICD.html)