Atoms in extreme virtual photon fields of fast, highly charged ions

Highly-charged ions at velocities close to the speed of light generate strong (I = 10"1"7 - 10"2"0 W/cm"2), ultra-short (t = 10"-"1"9 - 10"-"1"7 s) electromagnetic pulses when passing target atoms or molecules. Single and multiple ionization occurs and can be interpreted in terms of photoionization: at small field strength ionization is due to the absorption or the scattering of a single virtual photon whereas the incoherent, ''simultaneous'' absorption of ''many'' field quanta gives rise to multiple ionization in strong fields. In this paper analogies to photoionization are investigated by comparison of kinematically complete experimental data with results of various theoretical calculations for collisions of 100 MeV/u C"6"+, 1000 MeV/u U"9"2"+ and 3.6 MeV/u Au"5"3"+ on He, Ne and Ar targets. Dynamical multiple ionization mechanisms are identified as a function of the momentum transfer. Two-electron final states are found to sensitively depend on the correlated initial state, and the many-particle Coulomb continuum is investigated for triple ionization of neon in super-strong fields. (orig.)29 refs.SIGLEAvailable from TIB Hannover: RO 801(99-29) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Ultra-low energy electrons from fast heavy-ion helium collisions: the 'target Cusp'

Doubly differential cross sections d"2#sigma#/dv _p_a_r_a_l_l_e_l dv _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o have been obtained by mapping the 3-dimensional velocity space of ultra-low and low-energy electrons (1.5 meV#<=# E_e#<=#100 eV) emitted in singly ionizing 3.6 MeV/u Au"5"3"+ on helium collisions. A sharp (#DELTA#E_e _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o "F"W"H"M #<=# 22 meV) asymmetric peak centered at vertical stroke anti #nu# vertical stroke =0 is observed to emerge at ultra-low energies from the strongly forward shifted low-energy electron velocity distribution. The shape of this ''target cusp'', which is very sensitive on the details of the two-center potential, is in excellent accord with theoretical CTMC and CDW-EIS predictions. (orig.)Available from TIB Hannover: RO 801(98-61) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman