Ionization of molecular hydrogen by proton impact. II. Two-electron processes

Cross sections for double ionization and ionization plus excitation of ${\mathrm{H}}_2$ by high-energy protons are calculated as a function of the orientation of the ${\mathrm{H}}_2$ internuclear axis. Only the contributions of the double-collision process have been included. The ground state of ${\mathrm{H}}_2$ is described by Heitler-London-type wave functions, and the molecular orbitals for the excited states of ${\mathrm{H}}_2^{+}$ are constructed from atomic functions. The results have been compared with the data of Edwards et al. [Phys. Rev. A 42, 1367 (1990); 44, 797 (1991); Nucl. Instrum. Methods Phys. Res. B 53, 472 (1991)] and Ezell et al. [Nucl. Instrum. Methods Phys. Res. B 56/57, 292 (1991)]. The theoretical and measured cross sections have the same magnitude for double ionization. For the excitation of the 2p${\mathrm{\sigma }}_{\mathit{u}}$, 2p${\mathrm{\pi }}_{\mathit{u}}$, and 2s${\mathrm{\sigma }}_{\mathit{g}}$ states, the calculated cross sections are much lower than the measured ones.