The researchers from the University of Stuttgart and the University of Oklahoma told the BBC the so-called Rydberg molecule was theorized to form when one of its two atoms has an electron orbiting at an extreme distance from the atom's nucleus.
First predicted by physicist Chris Greene of the University of Colorado, the existence of the Rydberg molecule is consistent with quantum theories proposed in 1934 by Nobel prize-winning physicist Enrico Fermi, the researchers said.
The scientists said they observed a Rydberg molecule by super-cooling rubidium molecules to a temperature near absolute zero -- minus 273 degrees Celsius.
"We use an ultracold cloud of rubidium -- as you cool it, the atoms in the gas move closer together," Professor Vera Bendkowsky, who led the study at the University of Stuttgart, told the BBC. "The nuclei of the atoms have to be at the correct distance from each other for the electron fields to find each other and interact."
The scientists said they expect their findings to lead to the development of other novel molecules.
The research was reported in the journal Nature.