Swiss physicists managed to obtain a molecule “impossible” from the point of view of classical chemistry – a complex of an alkali metal atom and seven inert gas atoms, according to an article published in Physical Review Letters.
An unusual complex is formed upon laser excitation of cesium atoms introduced into a solid helium matrix at a temperature close to absolute zero and an increased pressure. Two new compounds – Cs * He2 and Cs * He7 – were identified by the fluorescence spectrum.
Calculations indicate a strange geometry of the complex – a flat seven-membered ring surrounds a metal atom. This symmetry has traditionally been considered an “exclusive” property of some organic molecules and is absent in crystalline substances. The researchers note that many doubted the possibility of synthesizing complexes with three or more helium atoms.
Excited complexes – exciplexes – violate the “usual” concepts of chemical bonding and require the use of serious quantum chemical methods to assess the properties. Peter Moroshkin, one of the authors of the article, claims that the discovered molecule is a convenient “testing ground” for testing a number of hypotheses in quantum chemistry and physics.
- Novel molecule makes its debut – PhysicsWeb, 18.02.2005
- Discovery of Dumbbell-Shaped Cs * HenExciplexes in Solid fourHe – Phys. Rev. Lett. 94, 063001 (2005), 18.02.2005
- Discovery of Dumbbell-Shaped Cs * HenExciplexes in Solid fourHe – Arxiv.org, 22.02.2005
- Exciplex Fluorescence Imaging Technique