Separation of the screening and antiscreening effects in the electron loss ofHe+onH2and He

The screening and antiscreening contributions to electron loss are separated experimentally through the measurement of the recoil ions and the emergent charge states in the collisions ${\mathrm{He}}^{+}$+(${\mathrm{H}}_2$,He) →${\mathrm{He}}^{2+}$+(${\mathrm{H}}_2^{+}$,${\mathrm{He}}^{+}$). The experimental data are in excellent agreement with calculations which include second-order contributions for the simultaneous ionization of the projectile and the target.