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  Home > JCE Print > Journal of Chemical Education > Issues > 2007  > May  >
Research: Science and Education
The Weakest Link: Bonding between Helium Atoms
Lawrence L. Lohr and S. M. Blinder
Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055
Cover
May 2007
Vol. 84 No. 5
p. 860
Abstract
Van der Waals attraction between helium atoms can lead to the formation of weakly-bound He2 diatomic molecules stable at temperatures in the millikelvin range. Helium dimers were first detected experimentally in 1993 and 1994. Sophisticated quantum-mechanical computations confirm that the He–He bond is the weakest known, with a binding energy corresponding to 1.176 mK, about 10-4 eV. The average internuclear distance is computed to be in excess of 50 Å, which makes He2 the largest known diatomic molecule as well. The authors have introduced an idealized deltafunction model for the helium dimer that succinctly represents its remarkable properties. Despite the weakness of each individual He–He bond, an intriguing mechanism exists for helium to form trimers and larger clusters with much greater binding energies.
Supplement
The deltafunction calulations for the helium dimer and variational computation on the helium trimer are available.
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Contents
  JCE2007p0860W.pdf
 
More Information
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Citation
Lohr, Lawrence L.; Blinder, S. M. J. Chem. Educ. 2007, 84, 860.
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Keywords
Atomic Properties / Structure; Computational Chemistry; Covalent Bonding; Graduate Education / Research; Helium; MO Theory; Molecular Properties / Structure; Noncovalent Interactions; Physical Chemistry; Quantum Chemistry; Textbooks / Reference Books; Theoretical Chemistry; Upper-Division Undergraduate
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History
Created:
Last Updated:
3/22/2007
3/27/2007
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