Multiple Ionization Dynamics in Extreme Fields:
From Atto- to Femtoseconds



Joachim Ullrich, Universität Freiburg

Highly-charged ions at velocities close to the speed of light generate extremely strong (I = 10¹⁸ - 10¹⁹ W/cm²), attosecond (t = 10^-19 - 10^-17 s) electromagnetic (half-) pulses when passing target atoms, molecules or clusters. Single and multiple ionization in such fields can be interpreted as an incoherent absorption of 'many' virtual photons (Weizsäcker-Williams method of equivalent photons). In kinematically complete experiments (GSI, Darmstadt), strong correlation between the emitted electrons in the continuum is found for double and triple ionization by means of intensity interferometry and using Dalitz-plots. Evidence is provided that the observed patterns are due to the ground state correlation. Recently, momentum distributions of Ne^1,2,3+ ions created in 30 fs laser pulses at a power density of 1 PW/cm² have been recorded at the Max-Born Institut, Berlin. Similarities and differences of multiple ionization dynamics in femtosecond laser fields or attosecond ion-induced half-pulses are illuminated. A possible future combination of both techniques is discussed.