PerspectiveChemistry

Molecule Formation in Ultrahigh Magnetic Fields

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Science  20 Jul 2012:
Vol. 337, Issue 6092, pp. 302-303
DOI: 10.1126/science.1224869

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Summary

Strong electric and magnetic fields tend to have opposite effects on the formation and structure of molecules. Strong electric fields always tend to separate the oppositely charged particles (electrons and nuclei), which causes molecules to ionize and dissociate. However, for strong homogeneous and static magnetic fields, binding can be strengthened. For hydrogen, the simplest atom, a certain class of its quantum states, including the ground state, becomes increasingly bound with increasing magnetic field strength (13). The electronic cloud shrinks transverse to the magnetic field, and because of the immediate proximity of the attractive nucleus, the overall energy decreases. This feature transfers to diatomic and linear-chain molecules, where the chemical binding energy increases and the corresponding bond distances decrease. The field strengths needed are far beyond the strongest available in the laboratory (30 to 40 T) but can be encountered in the atmospheres of magnetic white dwarfs (102 to 105 T) and neutron stars (>107 T). On page 327 of this issue, Lange et al. (4) show that, in addition to this diamagnetic enhanced binding, there exists an elementary paramagnetic bonding mechanism that occurs for the perpendicular orientation of a diatomic molecule with respect to the external magnetic field.