Cross sections for the single ionization of ${\mathrm{H}}_2$ forming ${\mathrm{H}}_2$${\mathrm{}}^{+}$(1s${\mathrm{\sigma }}_{\mathrm{g}}$) have been measured using ${\mathrm{H}}^{+}$ (${\mathrm{D}}^{+}$) and ${\mathrm{He}}^{+}$ projectiles. The energies of the ${\mathrm{H}}^{+}$ (${\mathrm{D}}^{+}$) projectiles ranged from 80 to 3500 keV/amu. The energies of the ${\mathrm{He}}^{+}$ projectiles ranged from 25 to 750 keV/amu. The results are compared with published data on the single ionization of helium by the same projectiles. For projectile energies above 200 keV/amu, the cross sections for the two targets differ by a factor of 2. Previously published measurements of the double-ionization cross sections of ${\mathrm{H}}_2$ and helium are also compared. The ${\mathrm{H}}_2$ cross section is smaller and falls off more rapidly with projectile velocity.

• Received 22 May 1986

DOI:https://doi.org/10.1103/PhysRevA.34.4411