Observations of Diatomic and Triatomic Hydrogen Negative Ions

Mass-spectrometric observations have been made of H${\mathrm{D}}^{-}$, ${\mathrm{D}}_2^{-}$, ${\mathrm{H}}_3^{-}$, ${\mathrm{H}}_2$ ${\mathrm{D}}^{-}$, H${\mathrm{D}}_2^{-}$, and ${\mathrm{D}}_3^{-}$, using a hollow-cathode duoplasmatron negative-ion source operating between 0.1 and 2 Torr. Both the diatomic and triatomic hydrogen negative ions appear stable, with half-lives greater than ${10}^{-5\mathrm{}}$ sec. Attenuation-cross-section measurements of ${\mathrm{D}}_2^{-}$ and ${\mathrm{D}}_3^{-}$ with helium between 3 and 5 keV yield average values of (5.5 and 7.0) × ${10}^{-15\mathrm{}}$ ${\mathrm{cm}}^2$, respectively.