Single and double electron capture from He targets by ${\mathrm{Ar}}^{16+}$ ions have been studied at projectile velocities from 0.3 to 1.5 a.u. Cold-target recoil-ion momentum spectroscopy was used to record the energy gain and scattering angle simultaneously. For single capture, the reaction window is found to spread in width approximately as the square root of the projectile velocity and to shift slightly toward smaller energy-gain values as the velocity increases. The angular distributions center at the half Coulomb angle over most of the velocity range covered, but differ in shape from multichannel Landau-Zener model results. For double capture, transfer ionization dominates and feeds primarily $n$-symmetric states, where n is the principal quantum number. True double capture feeds mainly $n$-asymmetric states. The angular distributions for double capture lie outside the half Coulomb angle, indicating the importance of two-step processes in populating doubly excited states.

In this work, we report experimental and theoretical ionization and electron-capture cross sections for single-, double- and triple-electron removal from ${\mathrm{H}}_2\mathrm{O}$ by ${\mathrm{Li}}^{3+}$ impact at energies ranging from 0.75 to 5.8 MeV. The experiment was carried out by selecting both the final charge state of the projectile and the ejected fragments in coincidence to obtain cross sections associated with ionization and electron-capture channels. The ionic fragments and the emitted electrons produced under single-collision conditions were collected by a time-of-flight spectrometer with single-hit (e.g., ${\mathrm{OH}}^{+}+{\mathrm{H}}^0)$ and double-hit events (e.g., ${\mathrm{OH}}^{+}+{\mathrm{H}}^{+})$ properly discriminated. For the one- and two-electron removal cases, the calculations based on the basis generator method for orbital propagation agree well with the experiment for most of the collision channels studied. Auger-electron emission after vacancy production in the inner $2a_1$ orbital of ${\mathrm{H}}_2\mathrm{O}$ is shown to have a substantial effect on the final charge-state distributions over the entire impact-energy interval.

Absolute total non-dissociative and partial dissociative cross sections of pyrimidine were measured for electron impact energies ranging from 70 to 400 eV and for proton impact energies from 125 up to 2500 keV. MOs ionization induced by coulomb interaction were studied by measuring both ionization and partial dissociative cross sections through time of flight mass spectrometry and by obtaining the branching ratios for fragment formation via a model calculation based on the Born approximation. The partial yields and the absolute cross sections measured as a function of the energy combined with the model calculation proved to be a useful tool to determine the vacancy population of the valence MOs from which several sets of fragment ions are produced. It was also a key point to distinguish the dissociation regimes induced by both particles. A comparison with previous experimental results is also presented.

Experimental cross sections for single and double ionization of ${\mathrm{H}}_2\mathrm{O}$ by swift ${\mathrm{H}}^{+}$ with energy ranging from 0.3 to 2.0 MeV are reported. In this energy range the ionization is the dominant collision process and charge transfer reactions can be disregarded. A multihit coincidence technique is used to measure the ${\text{H}}^{+}+{\text{OH}}^{+}$ and ${\text{H}}^{+}+{\text{O}}^{+}$ fragmentation channels. Single- and double-hit differential measurements together with a semiempirical calculation allow separating quantitatively the prompt and Auger-like decay contributions to fragmentation following a vacancy in the $2a_1$ molecular orbital. Concerning the double-ionization channel, it is found that for lower energies the mechanism of a sequential double-electron removal, known as TS2, dominates. For energies above above 750 keV/u ionization resulting from a single vacancy followed by an Auger like deexcitation takes over the TS2, becoming the main contribution to the double-ionization cross section. Our results are compared to the electron-impact data within the same velocity range and also with theoretical calculations available in the literature.

Cold-target recoil-ion-momentum spectroscopy (COLTRIMS) has been used to study single electron capture from He by ${\mathrm{Ar}}^{8+}$ ions at projectile velocities between 0.2 and 1.0 a.u. Populations of $3d$ through $7l$ states on the final ion are resolved, and angular distributions are presented for separated major final channels. As the projectile velocity is raised, the reaction window is observed to spread. Contrary to expectations based on a Landau-Zener picture of the process, higher $n$ and $l$ become favored with higher $v.\mathrm{}$ The results are in excellent agreement with coupled-channel calculations.

Cold target recoil ion momentum spectroscopy has been used to image the momentum distributions of continuum electrons liberated in the impact of slow ${\mathrm{He}}^{+}$ and ${\mathrm{He}}^{2+}$ ions on He. The distributions were measured for fully determined vector impact parameter. The spectra show that the electron momenta lie mainly in the collision plane and display a structure which strongly suggests that it is $\pi$ states which are dominantly promoted into the continuum in such collisions, but that interfering $\sigma$ and perhaps $\delta$ amplitudes are also important.