Hydrogen anion

The hydrogen anion is a negative hydrogen ion, H⁻. It is an important constituent of the atmosphere of stars, such as the Sun, where it is the dominant absorber of photons with energies in the range 0.75-0.4 eV, ranging from the infrared into the visible spectrum (Rau 1999). It also occurs in the Earth's ionosphere (Rau 1999).

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Its existence was first proven theoretically by Hans Bethe in 1929 (Bethe 1929). H⁻ is unusual because it has no bound excited states, as was finally proven in 1977 (Hill 1977). It has been studied experimentally using particle accelerators (Bryant 1977).

Chemical compounds that formally contain a hydrogen anion are called hydrides.

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