Electron capture and ionization processes were investigated for ${\mathrm{I}}^{\mathit{q}+}$-He and ${\mathrm{U}}^{\mathit{q}+}$-He collisions at incident energies 0.1–1.0 MeV/nucleon and for incident charge states q=5–44. Cross sections for single-electron capture, transfer ionization, single ionization, and double ionization were obtained using a projectile-ion recoil-ion coincidence technique. A pronounced interplay among the different electronic processes was observed. Cross sections for single ionization show a rather weak charge-state dependence, in disagreement with recent calculations of McKenzie and Olson [Phys. Rev. A 35, 2863 (1987)]. In a second experiment, photon recoil-ion coincidences were measured to obtain partial cross sections for capture into certain projectile n states. These measurements provide strong evidence that transfer ionization populates lower projectile n states than does single-electron capture. Zero-degree electron spectroscopy, coincident with charge capture for 0.5 MeV/nucleon ${\mathrm{U}}^{30+}$ projectiles revealed that the free electron in transfer ionization is released from the projectile to its continuum and from high-lying Rydberg states of the projectile.

L- and M-shell x-ray production cross sections have been measured for thin solid targets of neodymium, gadolinium, holmium, ytterbium, gold, and lead by 25-MeV ${}_{{\mathrm{}}^1{\mathrm{}}_6^2}{}^{}{}_{}{}^{}\mathrm{C}_{}^{\mathrm{q}+}{}_{}{}^{}$ (q=4,5,6) and by 32-MeV ${}_{{\mathrm{}}^1{\mathrm{}}_8^6}{}^{}{}_{}{}^{}\mathrm{O}_{}^{\mathrm{q}+}{}_{}{}^{}$ (q=5,7,8). The cross sections were determined from measurements made with thin targets (less than 2.25 μg/${\mathrm{cm}}^2$). For projectiles with one or two K-shell vacancies, the target x-ray production cross sections were found to be enhanced over those for projectiles without a K-shell vacancy. The sum of direct ionization to the continuum (DI) plus electron capture (EC) to the L,M,N,. . . shells and EC to the K shell of the projectile have been extracted from the data. The results are compared to the predictions of first Born theories, i.e., plane-wave Born approximation for DI and Oppenheimer-Brinkman-Kramers formula of Nikolaev for EC, and to the ECPSSR that accounts for energy loss and Coulomb deflection of the projectile as well as for relativistic and perturbed stationary states of inner-shell electrons.

We have observed dielectronic and direct excitation of H-like ${\mathrm{S}}^{15+}$ and ${\mathrm{Ca}}^{19+}$ and He-like ${\mathrm{Ti}}^{20+}$ ions in silicon channels caused by collision with weakly bound target electrons which behave as a free-electron gas. As in vacuo, relaxation of the doubly excited states can occur radiatively leading to ions of decreased charge, but in a crystal channel collisional effects can cause double ionization. The effects are seen in both the x-ray yields and charge-state fractions, and, in the case of ${\mathrm{Ti}}^{20+}$, in charge-state x-ray coincidences.

(1991). Resonant coherent excitation of Mg11+: Electronic collisions of state specified short-lived excited states in a crystal channel. Radiation Effects and Defects in Solids: Vol. 117, No. 1-3, pp. 73-77.

X rays produced in the collisions of 94–222-MeV ${\mathrm{O}}^{8+}$ ions with ${\mathrm{H}}_2$ and He targets have been measured. Resulting spectra have been analyzed to determine absolute yields, profile widths, and energies for x rays emitted in the process of radiative electron capture (REC). These measurements are compared with predictions based on impulse-approximation calculations, using differential cross sections for radiative recombination (RR) folded with target Compton profiles. Measured absolute peak energy positions and profiles are found to be in good agreement with these simple theoretical estimates. Cross sections derived from REC yields are compared with other measurements and with theoretical RR values. A small systematic discrepancy between experimental and theoretical cross sections is noted.