Structure and Stability of the Negative Hydrogen Molecular Ion

We present the results of a Coulomb explosion experiment that allows for the imaging of the rovibrational wave function of the metastable H-2(-) ion. Our measurements confirm the predicted large internuclear separation of 6 a.u., and they show that the ion decays by autodetachment rather than by spontaneous dissociation. Imaging of the resulting H-2 products reveals a large angular momentum of J = 25 +/- 2, quantifying the rotation that leads to the metastability of this most fundamental molecular anion.