We present the results of the detailed experimental study of multiple ionization of Ne and Ar by 25 and 7 fs laser pulses. Whereas in multiple ionization of Ar different mechanisms, involving field ionization steps and recollision-induced excitations, play a role, for Ne only one channel, where the highly correlated instantaneous emission of up to four electrons is triggered by a recollisional electron impact, is found to be important. Using few-cycle pulses we are able to suppress those processes that occur on time scales longer than one laser cycle.

The collision dynamics of He single ionization by 3.6 MeV/u Se28+ impact was explored using the reaction microscope of the Gesellschaft für Schwerionenforschung, a high-resolution integrated multielectron recoil-ion momentum spectrometer. The complete three-particle final-state momentum distribution (nine Cartesian components pi) was imaged with a resolution of Δpi≈±0.1 a.u. by measuring the three momentum components of the emitted electron and the recoiling target ion in coincidence. The projectile energy loss has been determined on a level of ΔEp/Ep≈10-7 and projectile scattering angles as small as Δϑ≈10-7 rad became accessible. The experimental data which are compared with results of classical trajectory Monte Carlo calculations reveal an unprecedented insight into the details of the electron emission and the collision dynamics for ionization of helium by fast heavy-ion impact.