Electron loss from 0.74 and 1.4 MeV/u low-charge-state argon and xenon ions colliding with neon, nitrogen, and argon

Absolute total, single, and multiple electron loss cross sections are measured for Ar"+-, Ar"2"+-, and Xe"3"+- Ne, N_2, Ar collisions at 0.74 and 1.4 MeV/u. In addition, a many-body Classical Trajectory Monte Carlo model was used to calculate total and multiple electron loss cross sections for Ar"+ impact. For N_2 and Ar targets, excellent agreement between the measured and calculated cross sections is found; for the Ne target the experimental data are approximately 40% smaller than the theoretical predictions. The experimental data are also used to examine cross section scaling characteristics for electron loss from fast, low-charge-state, heavy ions. It is shown that multiple electron loss increased the mean charge states of the outgoing argon and xenon ions by two and three respectively. The cross sections decreased with increasing number of electrons lost and scaled roughly as the inverse of the sum of the ionization potentials required to sequentially remove the most weakly bound, next most weakly bound, etc., electrons. This scaling was found to be independent of projectile, incoming charge state, and target. In addition, the experimental total loss cross sections are found to be nearly constant as a function of initial projectile charge state. As a function of impact energy, the theoretical predictions yield an E"-"1"/"3 behavior between 0.5 and 30 MeV/u for the total loss cross sections. Within error bars the data are consistent with this energy dependence but are also consistent with an E"-"1"/"2 energy dependence. (orig.)Available from TIB Hannover: RO 801(03-24) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Electron correlations observed through intensity interferometry

Intensity interferometry was applied to study electron correlations in doubly ionizing ion-atom collisions. In this method, the probability to find two electrons emitted in the same double ionization event with a certain momentum difference is compared to the corresponding probability for two uncorrelated electrons from two independent events. The ratio of both probabilities, the so-called correlation function, is found to sensitively reveal electron correlation effects, but it is rather insensitive to the collision dynamics. (orig.)12 refs.SIGLEAvailable from TIB Hannover: RO 801(99-28) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Momentum spectra for single and double electron ionization of He in relativistic collisions

The complete momentum spectra for single and double ionization of He by 1GeV/u (#beta#=0.88) U"9"2"+ have been investigated using a classical trajectory Monte Carlo method corrected for the relativistic projectile. The 1/r_1_2 electron-electron interaction has been included in the post-collision region for double ionization to incorporate the effects of both the nuclear-electron and electron-electron ionizing interactions, and to access the effects of electron correlation in the electron spectra. Experimental measurements were able to determine the longitudinal momentum spectra for single ionization; these observations are in accordance with the theoretical predictions for the three-body momentum balance between projectile, recoil ion, and ionized electron. In particular, the Lorentz contraction of the Coulomb interaction of the projectile manifests itself in the decrease of the post-collision interaction of the projectile with the electron and recoil ion, causing them to recoil back-to-back as in the case for a short electromagnetic pulse. This feature is clearly displayed in both the theoretical and experimental longitudinal momentum spectra, and by comparing to calculations that are performed at the same collision speed but do not include the relativistic potentials. Moreover, collision plane spectra of the three particles demonstrate that the momenta of the recoil ion and ionized electron are preferentially equal, and opposite, to each other. The electron spectra for double ionization show that the inclusion of the electron-electron interaction in the post-collision regime partitions the combined ionization momentum of the electrons so that the electrons are preferentially emitted in opposite azimuthal angles to one another. This is in contrast to calculations made assuming independent electrons. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Electron stripping cross sections for fast, low charge state uranium ions

Cross sections for projectile electron loss for U"1"0"+ and U"2"8"+ colliding with H_2, N_2 and Ar were calculated using the n-body classical trajectory Monte Carlo method. The calculations include electrons on both nuclear centers and all electron-electron and electron-nuclear interactions between centers. Multiple ionization is inherently included in these many electron calculations. Overall, except for the H_2 target where the projectile stripping is overestimated by a factor of two, the calculated cross sections are in reasonable accord with available data and the recent beam lifetime measurements from GSI-Darmstadt. For energies less than 100 MeV/u, the N_2 and Ar cross sections do not scale as E"-"1"."0 as predicted by one-electron theories. (orig.)Available from TIB Hannover: RO 801(04-17) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Complete single ionization momentum spectra for strong perturbation collisions

The combination of recoil ion and ionized electron momentum spectroscopy provides an unparalleled method to investigate the details of ion-atom collision dynamics in kinematically complete experiments. To predict singleionization scattering behavior at the level now realized by experiment, the classical trajectory three-body Monte Carlo method has been used to obtain complete momenta information for the ionized electron, recoil ion, and projectile in the collision plane defined by the incident projectile and outgoing recoil ion. Strongly coupled systems were considered where the charge state of the projectile divided by the speed of the collision q/v is greater than unity. Illustrated are 3.6 MeV/u Se"2"8"+ and 9.5 MeV/u Ni"2"6"+ collisions on He where experimental data are available. The theoretical results are in good agreement with these data and calculations have been performed for 165 keV/u and 506 keV/u C"6"++He to compare results for the same q/v perturbation strengths. (orig.)Available from TIB Hannover: RO 801(97-47) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Initial state dependence of low-energy electron emission in fast ion atom collisions

Single and multiple ionization of Neon and Argon atoms by 3.6 MeV/u Au"5"3"+ impact has been explored in kinematically complete experiments. Doubly differential cross sections for low-energy electron emission have been obtained for defined charge state of the recoiling target ion and the receding projectile. Observed target specific structures in the electron continuum are attributable to the nodal structure of the initial bound state momentum distribution. The experimental data are in excellent accord with CDW-EIS single ionization calculations if multiple ionization is considered appropriately. (orig.)21 refs.SIGLEAvailable from TIB Hannover: RO 801(99-20) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The dynamics of target single and double ionization induced by the virtual photon field of fast heavy ions

The collision dynamics of helium single and double ionization after impact of 3.6 MeV/u Se"2"8"+ projectiles has been explored using the high resolution electron - recoil-ion momentum spectrometer at GSI. The complete three particle final state in momentum space was determined with a resolution of #DELTA#p#approx##+-#0.1 a.u. in the case of single ionization by measuring the three momentum components of both, the emitted electron and the recoiling target-ion in coincidence. For double ionization the longitudinal momenta of both individual electrons were determined in coincidence with the recoil-ion. The electrons final momenta reflect the correlated motion in the ground state of helium (neon) during a time interval (collision time) which is short compared to the average revolution frequency. The ionization of the target atom shows correspondence to photodisintegration by the equivalent photon field of the passing fast highly charged projectile. (orig.)23 refs.Available from TIB Hannover: RO 801(96-48) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Detailed investigations of two-center collision dynamics

The combination of recoil ion and ionized electron momentum spectroscopy provides an unparalleled method to investigate the details of ion-atom collision dynamics. In order to predict scattering behavior and collaborate with experimental projects, the classical trajectory 3- and n-body Monte Carlo method has been modified to yield complete momenta information for ionized electron spectra in the collision plane defined by the incident projectile and outgoing projectile or recoil ion. To illuminate the richness of these spectra, calculations of 300 and 500 keV p and p- single ionization collisions with He are presented for low q/v perturbation strengths. For strong q/v collisions, the 100, 300 and 500 keV/u Ne"1"0"+ on He systems are illustrated. Strong asymmetry of the slow and saddle point electrons are predicted for antiproton and highly-charged Ne"1"0"+ projectiles. Furthermore, The electron capture to the continuum spectra for Ne"1"0"+ are observed to have not only the expected asymmetry in the longitudinal direction, but also a strong asymmetry in the collision plane. (orig.)Available from TIB Hannover: RO 801(96-39) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Complete momentum balance for single ionization of helium by fast ion impact: I. Experiment

The collision dynamics of He single ionization by 3.6 MeV/u Se"2"8"+ impact was explored using the GSI-reaction microscope, a high resolution integrated multi electron - recoil-ion momentum spectrometer. The complete three particle final state momentum distribution (9 cartesian components p_i) was imaged with a resolution of #DELTA#p_i #approx# #+-#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 #DELTA#E_p/E_p #approx# 10"-"7 and projectile scattering angles as small as #DELTA##theta# #approx# 10"-"7rad became accessible. The experimental data which are compared with results of classical trajectory Monte-Carlo (CTMC) 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. (orig.)Available from TIB Hannover: RO 801(97-12) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Full scale relativistic ab initio time dependent caculations for the the L-K vacancy transfer in 208 MeV Ni"2"3"+ on Ge solid target

We present full scale ab initio relativistic calculations for the L-K vacancy transfer in collisions of 208 MeV Ni"2"3"+ on Ge-solid target. Our time dependent Dirac-Fock-Slater method allows to achieve a very accurate quantitative explanation for the experimental impact parameter-dependent Ni-K and Ge-K vacancy probabilities recently measured at GSI. Darmstadt in terms of dynamic creation and annihilation of Ni n=2 shell vacancies in the collision. Our calculations reveal that both the radial and rotational coupling between the molecular levels contribute to the L-K vacancy transfer. (orig.)17 refs.Available from TIB Hannover: RO 801(95-82) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman