The negative ion of hydrogen

The negative ion of hydrogen continues to be important in atomic physics and astrophysics. Correlations between the two electrons are strong already in the ground state, the only bound state in this three-body system. This state attracted early interest, especially for the description of stellar atmospheres by Chandrasekhar and others. More recently, the rich spectrum of doubly-excited states, and the nature of the double escape above the break-up energy of 14.35 eV, have been central to our understanding of highly-correlated, non-separable problems in quantum physics. This article is a survey of the story of H- as it has developed over the last seventy years