Absolute charge-state-correlated cross sections for projectile electron loss, electron capture, and target multiple ionization in collisions between C 3+ ions and noble gases have been measured for energies between 1.3 and 3.5 MeV. The data have been compared with other similar absolute cross sections existent in the literature for several projectiles. Calculations for the single-loss−multiple-ionization channel have been performed for the screening mode, using both an extended version of the classical-impulse free-collision model and the plane-wave Born approximation (PWBA), and for the antiscreening mode within the PWBA. The energy dependence of the average number of target active electrons which contribute to the antiscreening has been described by means of a simple function, which is "universal" for noble gases but, in principle, projectile dependent. A method has been developed to obtain the number of active target electrons for each subshell in the high-velocity regime, which presented physically reasonable results. Analyses of the dependences of the single-capture and transfer-ionization (SC and TI, respectively) processes on the projectile charge states showed that, for He, equally charged bare and dressed projectiles have very similar cross sections; the latter thus acting as structureless point charges. A behavior similar to that in the SC has been observed for the pure single ionization of He by projectiles with different charge states and of the other noble gases by singly charged projectiles. It has been shown that the q 2 dependence of the pure-single and total-ionization cross sections, predicted by first-order models, is only valid for high-collision velocities. For slower collisions, the electron capture process becomes more relevant and competes with the ionization channel, a feature which grows in importance as the projectile charge state increases.

Absolute multiple-ionization cross sections, qϩ , of He (qϭ1,2), Ne (qϭ1,2,and 3͒, Ar (qϭ1,2,and 3͒, Kr (qϭ1,2,and 3͒, and Xe (qϭ1,2,3,and 4͒ atoms have been determined for interactions with He ϩ ions in the 1.0-3.5-MeV impact energy range. Special care was taken to obtain the slow recoil-ion detection efficiencies, by measuring the recoil ions in coincidence with the C 3ϩ capture channel and comparing these results with absolute single measurements. Comparison is made with the data available in the literature. The present results are in good agreement with the previously published data in the case of the helium target, but some nonsystematic discrepancies appear for heavier targets.

We have realized a mixed atomic and molecular trap, constituted by a Cs vapor-cell magneto-optical trap and a quadrupolar magnetic C s(2) trap, using the same magnetic field gradient. We observed the trapping of 2x 10(5) molecules, formed and accumulated in the metastable a (3)Sigma(+ )(u) state at a temperature of 30+/-10 microK through a approximately 150 ms photoassociation process. The lifetime of the trapped molecular cloud limited by the Cs background gas pressure is on the order of 1 s.

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The determination of the right balance between the strong-field interaction of the screened target nucleus and the two-center electron-electron interaction has been controversial since the early attempts to describe the stripping of light, swift ions, by heavy targets. In this work, we find a region of influence for the electron-electron contribution which clearly indicates that this interaction is an essential contribution to the stripping process for both light and heavy targets.

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