Electron-impact dissociation of C H2+ ions: Measurement of C H+ and C+ fragment ions

Absolute cross sections for electron-impact dissociation of C H2+ producing C H+ and C+ fragment ions were measured in the 3-100 eV range using a crossed electron-ion beams technique with total uncertainties of about 11% near the cross section peak. The cross sections are nearly identical for energies above 15 eV, but they are dramatically different at lower energies. The C H+ channel exhibits a strong peak rising from an observed threshold of about 6 eV; the C+ channel is relatively flat down to the lowest measured energy. Ionization cross sections for the C H2+ ion are also presented.