Quantum computation solves a half-century-old enigma: Elusive vibrational states of magnesium dimer found.

Yuwono, Stephen H; Magoulas, Ilias; Piecuch, Piotr · Sci Adv · 2020

basic_science · Level V

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Abstract

The high-lying vibrational states of the magnesium dimer (Mg<sub>2</sub>), which has been recognized as an important system in studies of ultracold and collisional phenomena, have eluded experimental characterization for half a century. Until now, only the first 14 vibrational states of Mg<sub>2</sub> have been experimentally resolved, although it has been suggested that the ground-state potential may support five additional levels. Here, we present highly accurate ab initio potential energy curves based on state-of-the-art coupled-cluster and full configuration interaction computations for the ground and excited electronic states involved in the experimental investigations of Mg<sub>2</sub>. Our ground-state potential unambiguously confirms the existence of 19 vibrational levels, with ~1 cm<sup>-1</sup> root mean square deviation between the calculated rovibrational term values and the available experimental and experimentally derived data. Our computations reproduce the latest laser-induced fluorescence spectrum and provide guidance for the experimental detection of the previously unresolved vibrational levels.