ELECTRON-CAPTURE IN COLLISIONS BETWEEN MEDIUM VELOCITY MULTIPLY CHARGED IONS AND H AND H-2

Experimental cross sections for single-electron capture by Dy-66(4+) (q = 4-20), Ta-73(q+) (q = 4-21), Re-75(q+) (q = 6-20), Au-79(q+) (q = 3-24) and U-92(q+) (q = 4-25) ions incident on H and H-2 targets have been measured at an energy of 100 keV/amu. The scaling of the capture cross sections with respect to the projectile charge is investigated for charge states q between 4 and 25. The general behavior of the cross sections is found to follow the prediction based on the Bohr-Lindhard theory. The measured cross sections at this energy are found to be roughly proportional to q2. The ratios of the cross sections measured on H-2 and H targets are found to lie between 1 and 2, and again this ratio is well described by the Bohr-Lindhard theory. For some of these ions, particularly Ta and Au, an oscillatory structure is superimposed on the secular q dependence. This structure, which has been observed earlier by Meyer et al. (Phys. Rev. A19, 515 (1979)), is suggested to be attributed to a core-dependent transfer-excitation (TE) mechanism.