Stable spin‐polarized atomic hydrogen

The strong attraction between hydrogen atoms of opposite electron spin would seem to make it impossible to have stable monatomic hydrogen gas, except in interstellar space. But the force between hydrogen atoms of parallel spin is predominantly repulsive. Isaac Silvera and Jook Walraven of the University of Amsterdam have taken advantage of the absence of bound states for spin‐polarized hydrogen to produce a monatomic hydrogen gas that showed no sign of reverting to ordinary $H2$ after almost an hour in a high magnetic field at low temperature, despite its very considerable density—more than $1016 atoms/cm3.$