Magnetic-field imaging of weakly bound levels of the ground-state Na2 dimer -: art. no. 023412

We measured in a molecular-beam experiment the magnetic-field dependence of the last bound levels of the X (1)Sigma(g)(+) and a (3)Sigma(u)(+) potentials close to the 3s + 3s asymptote Na-2. The field behavior of these levels in an external magnetic field differs for even or odd nuclear mechanical angular momentum, Coupled-channel calculations using high-precision potentials for the X (1)Sigma(g)(+) and a (3)Sigma(u)(+) potentials give excellent quantitative agreement between experiment and theory. Our data lead to a precise and quantitative description of the magnetic decoupling of the singlet and triplet manifold and of Feshbach resonances in a cold atomic collision.