Correlated multi-electron dynamics in ultrafast laser pulse - atom   interactions
  We present the results of the detailed experimental study of multiple ionization of Ne and Ar by 25 and 7 fs laser pulses. For Ne the highly correlated "instantaneous" emission of up to four electrons is triggered by a recollisional electron impact, whereas in multiple ionization of Ar different mechanisms, involving field ionization steps and recollision-induced excitations, play a major role. Using few-cycle pulses we are able to suppress those processes that occur on time scales longer than one laser cycle. 
A. Rudenko, K. Zrost, B. Feuerstein, V.L.B. de Jesus, C.D. Schr\"oter,   R. Moshammer, J. Ullrich