Beryllium Dimer—Caught in the Act of Bonding

Abstract

2 Be or Not 2 Be? The beryllium dimer is a rather simple-looking compound, bridging two atoms of the fourth-lightest element. Yet it has long posed a frustrating challenge to theorists, because, to a first approximation, chemical bonding models suggest that it should not exist. In recent decades, calculations of ever-increasing sophistication have offered rationales for the two atoms' puzzling mutual attraction. Now Merritt et al. (p. 1548 , published online 21 May; see the Perspective by Bernath ) have used high-resolution spectroscopy to assemble, at last, a full experimental potential energy function describing the ground electronic state of Be 2 . The curve is unusually shallow at long bond lengths, deviating from the contour of more traditional molecular Morse potentials, and provides a detailed basis of comparison for future theoretical bonding frameworks.