Ground State of Atoms and Molecules in a Superstrong Magnetic Field

In superstrong magnetic fields, of the order of magnitude supposed to exist in neutron stars, atoms are characterized by enormous binding energies, small dimensions, and a very elongated distribution of charge having approximately the shape of a concave-ended cylinder. Their ionization energies have a monotonic dependence on the atomic number, and tend to level off at high $Z$; the very peculiar distribution of charge favors the formation of negative ions. When the magnetic field increases, nuclei tend to align and share their electrons, forming linear molecules. These features are very different from those of ordinary matter, and may have important astrophysical consequences, e.g., on the emission of charged particles from the surface of a magnetic neutron star, or the structure of its crust.