Defining Diberyllium

Eight decades after Chemistry Nobel Laureate Gerhard Herzberg first tried to synthesize Be₂, a research team led by Michael C. Heaven of Emory University has created and spectroscopically characterized the ground state of the elusive molecule (Science, DOI: 10.1126/science.1174326). Diberyllium has been the focus of countless theoretical studies over the years: Simple valence bond theory predicts a bond order of zero for Be₂ although a bonded molecule has been observed in the gas phase, and researchers have questioned whether Be₂ has a real chemical bond or merely a weak van der Waals interaction. Heaven and colleagues formed gaseous Be₂ by pulsed-laser vaporization of beryllium metal, then conducted laser excitation experiments to illuminate all of the bound vibrational levels of the ground state of the molecule. They found that Be₂ has a bond length of 2.45 Å, a dissociation energy of 2.6 kcal/mol, and a uniquely shaped potential energy curve. The experimental results should provide a benchmark by which to evaluate theoretical models and procedures, the researchers say, and could inspire efforts to prepare isolable Be–Be compounds.