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Full-Text Articles in Physics

Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz Jul 2019

Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz

Michael Schulz

We have measured fully differential cross sections (FDCS) for ionization in 75-keVp+H2 collisions for ejected electron speeds close to the projectile speed. The data were analyzed in dependence on both the electron emission angle and the projectile scattering angle. Pronounced postcollisional effects between the projectile and the ejected electrons were observed. Significant differences between experiment and theory and between two conceptually very similar theoretical models were found. This shows that in the region of electron-projectile velocity-matching the FDCS is very sensitive to the details of the underlying few-body dynamics.


Two-Center Interferences In Dielectronic Transitions In H2++ He Collisions, Shaofeng Zhang, Daniel Fischer, Michael Schulz, Alexander B. Voitkiv, Arne Senftleben, Alexander Dorn, Joachim Hermann Ullrich, Xinwen Ma, Robert Moshammer Feb 2018

Two-Center Interferences In Dielectronic Transitions In H2++ He Collisions, Shaofeng Zhang, Daniel Fischer, Michael Schulz, Alexander B. Voitkiv, Arne Senftleben, Alexander Dorn, Joachim Hermann Ullrich, Xinwen Ma, Robert Moshammer

Michael Schulz

Molecular two-center interferences in a collision induced excitation of H2+ projectile ions, with simultaneous ionization of helium target atoms, are investigated in a kinematically complete experiment. In the process under investigation, the helium atom is singly ionized and simultaneously the molecular hydrogen ion is dissociated. Different collision mechanisms are identified and interference fringes emerging from a correlated first-order mechanism and from an independent second-order process are observed.


X-Ray Emission From Slow Highly Charged Ar Ions Interacting With A Ge Surface, Michael Schulz, C. Lewis Cocke, Siegbert Hagmann, Martin P. Stockli, Horst Schmidt-Bocking Feb 2018

X-Ray Emission From Slow Highly Charged Ar Ions Interacting With A Ge Surface, Michael Schulz, C. Lewis Cocke, Siegbert Hagmann, Martin P. Stockli, Horst Schmidt-Bocking

Michael Schulz

We have measured K x-ray spectra and yields from Ar17+ ions slowly approaching a single-crystal Ge surface. The yields were measured as a function of the projectile velocity component perpendicular to the surface. From the data a characteristic time of approximately 1 psec was extracted for the in-flight filling above the surface of the Ar K vacancy.


Three-Body Coulomb Problem Probed By Mapping The Bethe Surface In Ionizing Ion-Atom Collisions, Robert Moshammer, Appathurai N. Perumal, Michael Schulz, V. D. Rodriguez, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich Feb 2018

Three-Body Coulomb Problem Probed By Mapping The Bethe Surface In Ionizing Ion-Atom Collisions, Robert Moshammer, Appathurai N. Perumal, Michael Schulz, V. D. Rodriguez, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich

Michael Schulz

The three-body Coulomb problem has been explored in kinematically complete experiments on single ionization of helium by 100 MeV / u C 6 + and 3.6 MeV / u u 5 3 + impact. Low-energy electron emission (E e < 150 eV ) as a function of the projectile deflection ϑ p (momentum transfer), i.e., the Bethe surface [[15]], has been mapped with Δ ϑ p ± 25 nanoradian resolution at extremely large perturbations (3.6 MeV / uAu53+ ) where single ionization occurs at impact parameters of typically 10 times the He K -shell radius. The experimental data are not in agreement with state-of-the-art continuum distorted wave-eikonal initial state theory.


Strongly Enhanced Backward Emission Of Electrons In Transfer And Ionization, Michael Schulz, Xincheng Wang, M. Gundmundsson, Katharina R. Schneider, Aditya H. Kelkar, Alexander B. Voitkiv, B. Najjari, Markus S. Schoffler, Lothar Ph H H Schmidt, Reinhard Dorner, Joachim Hermann Ullrich, Robert Moshammer, Daniel Fischer Feb 2018

Strongly Enhanced Backward Emission Of Electrons In Transfer And Ionization, Michael Schulz, Xincheng Wang, M. Gundmundsson, Katharina R. Schneider, Aditya H. Kelkar, Alexander B. Voitkiv, B. Najjari, Markus S. Schoffler, Lothar Ph H H Schmidt, Reinhard Dorner, Joachim Hermann Ullrich, Robert Moshammer, Daniel Fischer

Michael Schulz

We studied three-dimensional angular distributions and longitudinal momentum spectra of electrons ejected in transfer plus ionization (TI), i.e., the ejection of one and the capture of a second target electron, for ion-helium collisions. We observe a pronounced structure strongly focused opposite to the projectile beam direction, which we associate with a new correlated TI mechanism proposed recently. This process contributes significantly to the total cross sections over a broad range of perturbations η, even at η as large as 0.5, where uncorrelated TI mechanisms were thought to be dominant.


State-Selective Capture In Collisions Of Protons With Noble Gases, Michael Schulz, D. M. Blankenship, S. W. Bross, A. D. Gaus, Timothy Gay, W. T. Htwe, John T. Park, Jerry Peacher Feb 2018

State-Selective Capture In Collisions Of Protons With Noble Gases, Michael Schulz, D. M. Blankenship, S. W. Bross, A. D. Gaus, Timothy Gay, W. T. Htwe, John T. Park, Jerry Peacher

Michael Schulz

We have measured coincidences between neutral H atoms and Lyman-α photons for collisions between 50-keV protons and noble gases as a function of the projectile scattering angle. The coincidences are dominated by capture to the 2p state of the projectile. While the total cross sections depend strongly on the target, the shape of the angular distribution of the differential cross sections was found to depend only weakly on that parameter. The data indicate that electrons are captured predominantly from the outermost shell of the target atom for the collision systems studied here.


Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Aaron Laforge, Kisra Egodapitiya, Sachin Sharma, Michael Schulz Feb 2018

Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Aaron Laforge, Kisra Egodapitiya, Sachin Sharma, Michael Schulz

Michael Schulz

We have measured and calculated doubly differential cross sections for ionization of atomic hydrogen using 75-keV proton impact for fixed projectile energy losses as a function of scattering angle.


Target Electron Ionization In Li2+-L-Li Collisions: A Multi-Electron Perspective, Maciej Dominik Piewanowski, Laszlo Gulyas, Marko W. Horbatsch, Johannes Goullon, Natalia Ferreira, Renate Hubele, Vitor L B D De Jesus, H. Lindenblatt, Katharina R. Schneider, Michael Schulz, Michael Schuricke, Z. Song, Shaofeng Zhang, Daniel Fischer, Tom Kirchner Feb 2018

Target Electron Ionization In Li2+-L-Li Collisions: A Multi-Electron Perspective, Maciej Dominik Piewanowski, Laszlo Gulyas, Marko W. Horbatsch, Johannes Goullon, Natalia Ferreira, Renate Hubele, Vitor L B D De Jesus, H. Lindenblatt, Katharina R. Schneider, Michael Schulz, Michael Schuricke, Z. Song, Shaofeng Zhang, Daniel Fischer, Tom Kirchner

Michael Schulz

Target electron removal in Li2+-Li collisions at 2290 keV/amu is studied experimentally and theoretically for ground and excited lithium target configurations. It is shown that in outer-shell ionization a single-electron process plays the dominant part. However, the K-shell ionization results are more difficult to interpret. According to our calculations, the process is shown to be strongly single-particle like. On one hand, a high resemblance between theoretical single-particle ionization and exclusive inner-shell ionization is demonstrated, and contributions from multi-electron processes are found to be weak. On the other hand, it is indicated by the discrepancy between experimental and ...


State Selective Scattering Angle Dependent Capture Cross Sections Measured By Cold Target Recoil Ion Momentum Spectroscopy, Volker Mergel, Reinhard Dorner, Joachim Hermann Ullrich, Ottmar Jagutzki, Sergio Lencinas, S. Nuttgens, Lutz Spielberger, Marc Unverzagt, C. Lewis Cocke, Ronald E. Olson, Michael Schulz, Udo Buck, E. Zanger, W. Theisinger, M. Isser, S. Geis, Horst Schmidt-Bocking Feb 2018

State Selective Scattering Angle Dependent Capture Cross Sections Measured By Cold Target Recoil Ion Momentum Spectroscopy, Volker Mergel, Reinhard Dorner, Joachim Hermann Ullrich, Ottmar Jagutzki, Sergio Lencinas, S. Nuttgens, Lutz Spielberger, Marc Unverzagt, C. Lewis Cocke, Ronald E. Olson, Michael Schulz, Udo Buck, E. Zanger, W. Theisinger, M. Isser, S. Geis, Horst Schmidt-Bocking

Michael Schulz

We have developed a new kind of recoil ion momentum spectroscopy technique, using a precooled supersonic gas jet target, to determine state selective, scattering angle dependent cross sections for swift ion-atom collisions ( 0. 25 , ..., , 1 MeV He2+ on He), by measuring the transverse and longitudinal momentum of the recoil ion. A longitudinal momentum resolution of ± 0.13 a. u. was achieved, about a factor of 30 better than ever obtained before, which enables a clear separation of K and L shell capture. In the transverse direction a resolution corresponding to a projectile scattering angle uncertainty of Δ ϑ P ...


Systematic Analysis Of Double-Ionization Dynamics Based On Four-Body Dalitz Plots, Daniel Fischer, Michael Schulz, Katharina R. Schneider, Marcelo F. Ciappina, Tom Kirchner, Aditya H. Kelkar, S. Hagman, Manfred Grieser, Kai Uwe Kuhnel, Robert Moshammer, Joachim Hermann Ullrich Feb 2018

Systematic Analysis Of Double-Ionization Dynamics Based On Four-Body Dalitz Plots, Daniel Fischer, Michael Schulz, Katharina R. Schneider, Marcelo F. Ciappina, Tom Kirchner, Aditya H. Kelkar, S. Hagman, Manfred Grieser, Kai Uwe Kuhnel, Robert Moshammer, Joachim Hermann Ullrich

Michael Schulz

We report on an experimental and theoretical systematic study of double ionization of helium by ion impact in terms of four-particle Dalitz plots. Several collision systems covering abroad range of perturbation parameters η (projectile charge to speed ratio) were investigated. With increasing η we observe a systematic trend from features, characteristic to correlated double-ionization mechanisms, to signatures of higher-order processes not requiring electron-electron correlations [the mechanism called "two-step-two projectile-electron interaction" (TS-2)]. The data for the largest η can qualitatively be amazingly well described by a simple model only including the TS-2 mechanism.


Resonant Transfer And Excitation In Li-Like F Colliding With H2, Michael Schulz, Reinhold S. Schuch, Sheldon Datz, Edson L B Justiniano, Philip D. Miller, Harald Schone Feb 2018

Resonant Transfer And Excitation In Li-Like F Colliding With H2, Michael Schulz, Reinhold S. Schuch, Sheldon Datz, Edson L B Justiniano, Philip D. Miller, Harald Schone

Michael Schulz

We have measured coincidences between x rays and projectiles that have captured one electron in F6+ + H2 collisions at projectile energies between 15 and 33 MeV. The cross sections for capture and simultaneous x-ray emission as a function of projectile energy show clear structures. Indications of an unexpectedly high population of high-n states predominantly formed by resonant transfer and excitation (RTE) were found. Above the Kln (n>1) RTE resonance energies another maximum was observed.


Single Transfer-Excitation Resonance Observed Via The Two-Photon Decay In He-Like Ge30+, Paul H. Mokler, S. Reusch, A. Warczak, Zbigniew Stachura, T. Kambara, Alfred K. Muller, Reinhold S. Schuch, Michael Schulz Feb 2018

Single Transfer-Excitation Resonance Observed Via The Two-Photon Decay In He-Like Ge30+, Paul H. Mokler, S. Reusch, A. Warczak, Zbigniew Stachura, T. Kambara, Alfred K. Muller, Reinhold S. Schuch, Michael Schulz

Michael Schulz

We measured the 2E1 decay of the 1s2s 1S0 →1s2 1S0 transition in He-like germanium for 12- to 19-MeV/u Ge31+ +H2 collisions. The resonant population of the 2s2p 1P1 state by transfer excitation was isolated due to its cascading to the 1s2s 1S0 state. The experimental cross sections compare well with calculations using dielectronic recombination rates. The method gives the unique possibility to populate selectively the 1S0 state in heavy He-like ions.


Scattering-Angle Dependence Of Doubly Differential Cross Sections For Fragmentation Of H2 By Proton Impact, Kisra N. Egodapitiya, Sachin D. Sharma, Aaron C. Laforge, Michael Schulz Feb 2018

Scattering-Angle Dependence Of Doubly Differential Cross Sections For Fragmentation Of H2 By Proton Impact, Kisra N. Egodapitiya, Sachin D. Sharma, Aaron C. Laforge, Michael Schulz

Michael Schulz

We have measured double differential cross sections (DDCS) for proton fragment formation for fixed projectile energy losses as a function of projectile scattering angle in 75 keV p + H2 collisions. An oscillating pattern was observed in the angular dependence of the DDCS with a frequency about twice as large as what we found earlier for nondissociative ionization. Possible origins for this frequency doubling are discussed.


Role Of Projectile Coherence In Close Heavy Ion-Atom Collisions, Katharina R. Schneider, Michael Schulz, Xincheng Wang, Aditya H. Kelkar, Manfred Grieser, Claude Krantz, Joachim Hermann Ullrich, Robert Moshammer, Daniel Fischer Feb 2018

Role Of Projectile Coherence In Close Heavy Ion-Atom Collisions, Katharina R. Schneider, Michael Schulz, Xincheng Wang, Aditya H. Kelkar, Manfred Grieser, Claude Krantz, Joachim Hermann Ullrich, Robert Moshammer, Daniel Fischer

Michael Schulz

We have measured fully differential cross sections for single ionization and transfer ionization (TI) in 16 MeV O7++He collisions. The impact parameters mostly contributing to single ionization are about an order of magnitude larger than for TI. Therefore, the projectile beam was much more coherent for the latter compared to the former process. The measured data suggest that, as a result, TI is significantly affected by interference effects which are not present in single ionization.


Separated Resonances In Simultaneous Capture And Excitation Of S15+ In H2 Observed By K-X-Ray K-X-Ray Coincidences, Michael Schulz, Edson L B Justiniano, Reinhold S. Schuch, Paul H. Mokler, S. Reusch Feb 2018

Separated Resonances In Simultaneous Capture And Excitation Of S15+ In H2 Observed By K-X-Ray K-X-Ray Coincidences, Michael Schulz, Edson L B Justiniano, Reinhold S. Schuch, Paul H. Mokler, S. Reusch

Michael Schulz

We have measured cross sections for the correlated emission of two K x rays following the collision of hydrogenlike sulfur ions with H2 in the energy range between 70 and 160 MeV. The observation of the two correlated x rays is interpreted as a resonant capture of a target electron accompanied by simultaneous excitation of the projectile in the collision (RTE). By our distinguishing between Kα and Kβ lines, contributions from KLL and KLn (n≥M) resonances could be determined independently.


Simultaneous Projectile-Target Ionization: A Novel Approach To (E, 2e) Experiments On Ions, Holger Kollmus, Robert Moshammer, Ronald E. Olson, Siegbert Hagmann, Michael Schulz, Joachim Hermann Ullrich Feb 2018

Simultaneous Projectile-Target Ionization: A Novel Approach To (E, 2e) Experiments On Ions, Holger Kollmus, Robert Moshammer, Ronald E. Olson, Siegbert Hagmann, Michael Schulz, Joachim Hermann Ullrich

Michael Schulz

A kinematically complete experiment for simultaneous ionization of a projectile and target has been performed for 3.6 MeV/u C2+ on He collisions measuring the final vector momenta of the He1+ recoil ion and of two electrons (projectile, target) in coincidence with the emerging C3+ projectile. The feasibility of an event-by-event separation of the various reaction channels, among them the ionization of C2+ by the interaction with a quasifree target electron, is demonstrated in agreement with six-body classical trajectory Monte Carlo calculations, paving the way to kinematically complete electron-ion scattering experiments.


Projectile Coherence Effects In Electron Capture By Protons Colliding With H2 And He, Sachin D. Sharma, Ahmad Hasan, Kisra N. Egodapitiya, T. P. Arthanayaka, G. Sakhelashvili, Michael Schulz Feb 2018

Projectile Coherence Effects In Electron Capture By Protons Colliding With H2 And He, Sachin D. Sharma, Ahmad Hasan, Kisra N. Egodapitiya, T. P. Arthanayaka, G. Sakhelashvili, Michael Schulz

Michael Schulz

We have measured differential cross sections for single and dissociative capture for 25 and 75 keV protons colliding with H2 and He. Significant differences were found depending on whether the projectile beam was coherent or incoherent. For 75 keV p+H2 these differences can be mostly associated with molecular two-center interference and possibly some contributions from path interference. For 25 keV (both targets) they are mostly due to path interference between different impact parameters leading to the same scattering angles and, for the H2 target, possibly some contributions from molecular two-center interference.


Probing Scattering Wave Functions Close To The Nucleus, Don H. Madison, Daniel Fischer, Matthew S. Foster, Michael Schulz, Robert Moshammer, Stephenie J. Jones, Joachim Hermann Ullrich Feb 2018

Probing Scattering Wave Functions Close To The Nucleus, Don H. Madison, Daniel Fischer, Matthew S. Foster, Michael Schulz, Robert Moshammer, Stephenie J. Jones, Joachim Hermann Ullrich

Michael Schulz

Recently, three-dimensional imaging of the ejected electrons following 100  MeV/amu C6+ single ionization of helium led to the observation of a new structure not predicted by theory [M. Schulz et al., Nature (London) 422, 48 (2003)]. Instead of the usual “recoil lobe” centered on the momentum-transfer axis, a ring-shaped structure centered on the beam axis was observed. New measurements at 2  MeV/amu exhibit a similar structure, which is now predicted by theory. We argue that the same theory failed at 100  MeV/amu because the faster projectiles probe distances much closer to the nucleus, where our multiple-scattering ...


Postcollision Effects In Target Ionization By Ion Impact At Large Momentum Transfer, Michael Schulz, B. Najjari, Alexander B. Voitkiv, Katharina R. Schneider, Xincheng Wang, Aaron C. Laforge, Renate Hubele, Johannes Goullon, Natalia Ferreira, Aditya H. Kelkar, Manfred Grieser, Robert Moshammer, Joachim Hermann Ullrich, Daniel Fischer Feb 2018

Postcollision Effects In Target Ionization By Ion Impact At Large Momentum Transfer, Michael Schulz, B. Najjari, Alexander B. Voitkiv, Katharina R. Schneider, Xincheng Wang, Aaron C. Laforge, Renate Hubele, Johannes Goullon, Natalia Ferreira, Aditya H. Kelkar, Manfred Grieser, Robert Moshammer, Joachim Hermann Ullrich, Daniel Fischer

Michael Schulz

We have measured and calculated fully differential cross sections for target ionization in 16-MeV O7++He and 24-MeV O8++Li collisions. As in previous studies, in the case of the He target we observe a pronounced forward shift in the angular distribution of the electrons relative to the direction of the momentum transfer q at small q (q < 1 a.u.). An unexpected result is that we also find a strong forward shift at large q (q > 2 a.u.), while at intermediate q this shift becomes very weak or even turns into a backward shift. For the Li target, in contrast, the forward shift monotonically increases with increasing q. These observations are qualitatively reproduced by our ...


Resonant Dielectronic And Direct Excitation In Crystal Channels, Sheldon Datz, Charles Randy Vane, Peter F. Dittner, J. P. Giese, J. C. Gomez Del Campo, N. L. Jones, Herbert F. Krause, Philip D. Miller, Michael Schulz, Harald Schone, Thomas M. Rosseel Feb 2018

Resonant Dielectronic And Direct Excitation In Crystal Channels, Sheldon Datz, Charles Randy Vane, Peter F. Dittner, J. P. Giese, J. C. Gomez Del Campo, N. L. Jones, Herbert F. Krause, Philip D. Miller, Michael Schulz, Harald Schone, Thomas M. Rosseel

Michael Schulz

We have observed dielectronic and direct excitation of H-like S15+ and Ca19+ and He-like Ti20+ ions in silicon channels caused by collision with weakly bound target electrons which behave as a free-electron gas. As in vacuo, relaxation of the doubly excited states can occur radiatively leading to ions of decreased charge, but in a crystal channel collisional effects can cause double ionization. The effects are seen in both the x-ray yields and charge-state fractions, and, in the case of Ti20+, in charge-state x-ray coincidences.


Projectile Energy Loss In Multiply Ionizing Ion-Atom Collisions, Harald Schone, Reinhold S. Schuch, Sheldon Datz, Michael Schulz, Peter F. Dittner, J. P. Giese, Quentin C. Kessel, Herbert F. Krause, Philip D. Miller, Charles Randy Vane Feb 2018

Projectile Energy Loss In Multiply Ionizing Ion-Atom Collisions, Harald Schone, Reinhold S. Schuch, Sheldon Datz, Michael Schulz, Peter F. Dittner, J. P. Giese, Quentin C. Kessel, Herbert F. Krause, Philip D. Miller, Charles Randy Vane

Michael Schulz

The projectile energy loss for 7.5--25-MeV C6+,5+ and F6+ ions was measured for single collisions with He, Ne, Ar, and Kr as a function of the recoil-ion charge state and the projectile scattering. This energy loss was measured for collisions in which the projectile captured an electron and for those involving just direct ionization. We investigated and found a large average energy transfer (100--250 eV/electron) to the continuum electrons. A strong increase of the scattering angle with recoil-ion charge state was observed for both capture and direct ionization. The results imply that, for smaller impact ...


Polarization And Interference Effects In Ionization Of Li By Ion Impact, Renate Hubele, Aaron C. Laforge, Michael Schulz, Johannes Goullon, Xincheng Wang, B. Najjari, Natalia Ferreira, Manfred Grieser, Vitor L B D De Jesus, Robert Moshammer, Katharina R. Schneider, Alexander B. Voitkiv, Daniel Fischer Feb 2018

Polarization And Interference Effects In Ionization Of Li By Ion Impact, Renate Hubele, Aaron C. Laforge, Michael Schulz, Johannes Goullon, Xincheng Wang, B. Najjari, Natalia Ferreira, Manfred Grieser, Vitor L B D De Jesus, Robert Moshammer, Katharina R. Schneider, Alexander B. Voitkiv, Daniel Fischer

Michael Schulz

We present initial-state selective fully differential cross sections for ionization of lithium by 24 MeV O8+ impact. The data for ionization from the 2s and 2p states look qualitatively different from each other and from 1s ionization of He. For ionization from the 2p state, to which in our study the mL=-1 substate predominantly contributes, we observe orientational dichroism and for 2s ionization pronounced interference which we trace back to the nodal structure of the initial-state wave function.


Reaction Dynamics In Double Ionization Of Helium By Electron Impact, Marcelo F. Ciappina, Michael Schulz, Tom Kirchner Feb 2018

Reaction Dynamics In Double Ionization Of Helium By Electron Impact, Marcelo F. Ciappina, Michael Schulz, Tom Kirchner

Michael Schulz

We present theoretical fully differential cross sections (FDCS) for double ionization of helium by 500 eV and 2 keV electron impact. Contributions from various reaction mechanisms to the FDCS were calculated separately and compared to experimental data. Our theoretical methods are based on the first Born approximation. Higher-order effects are incorporated using the Monte Carlo event generator technique. Earlier, we successfully applied this approach to double ionization by ion impact, and in the work reported here it is extended to electron impact. We demonstrate that at 500 eV impact energy, double ionization is dominated by higher-order mechanisms. Even at 2 ...


Population Of Highly Excited Intermediate Resonance States By Electron Transfer And Excitation, Reinhold S. Schuch, Edson L B Justiniano, Michael Schulz, Sheldon Datz, Peter F. Dittner, J. P. Giese, Herbert F. Krause, Harald Schone, Charles Randy Vane, Stephen M. Shafroth Feb 2018

Population Of Highly Excited Intermediate Resonance States By Electron Transfer And Excitation, Reinhold S. Schuch, Edson L B Justiniano, Michael Schulz, Sheldon Datz, Peter F. Dittner, J. P. Giese, Herbert F. Krause, Harald Schone, Charles Randy Vane, Stephen M. Shafroth

Michael Schulz

Coincidences between two sulfur K x rays were detected from collisions of hydrogenlike S ions with H2 gas in the projectile energy range between 150 and 225 MeV. These K x rays are emitted in the decay of doubly excited states formed in the collisions via transfer and excitation. The excitation function for two coincident Kβ transitions peaks at about 175 MeV, slightly above the expected KMM resonance energy for resonant transfer and excitation (RTE). This demonstrates the occurrence of ΔN≥2 transitions (i.e., KMM and higher resonances) in the RTE process. The cross sections for the population ...


Ion-Lithium Collision Dynamics Studied With A Laser-Cooled In-Ring Target, Daniel Fischer, Dominik Globig, Johannes Goullon, Manfred Grieser, Renate Hubele, Vitor L B D De Jesus, Aditya H. Kelkar, Aaron C. Laforge, H. Lindenblatt, Deepankar S. Misra, B. Najjari, Katharina R. Schneider, Michael Schulz, Martin Sell, Xincheng Wang Feb 2018

Ion-Lithium Collision Dynamics Studied With A Laser-Cooled In-Ring Target, Daniel Fischer, Dominik Globig, Johannes Goullon, Manfred Grieser, Renate Hubele, Vitor L B D De Jesus, Aditya H. Kelkar, Aaron C. Laforge, H. Lindenblatt, Deepankar S. Misra, B. Najjari, Katharina R. Schneider, Michael Schulz, Martin Sell, Xincheng Wang

Michael Schulz

We present a novel experimental tool allowing for kinematically complete studies of break-up processes of laser-cooled atoms. This apparatus, the 'MOTReMi,' is a combination of a magneto-optical trap (MOT) and a reaction microscope (ReMi). Operated in an ion-storage ring, the new setup enables us to study the dynamics in swift ion-atom collisions on an unprecedented level of precision and detail. In the inaugural experiment on collisions with 1.5MeV/amu O8 +-Li the pure ionization of the valence electron as well as the ionization-excitation of the lithium target was investigated.


Mutual Projectile And Target Ionization In 1-Mev/Amu N4+ And N5++ He Collisions, Xincheng Wang, Katharina R. Schneider, Aditya H. Kelkar, Gunterschul Brenner, Michael Schulz, B. Najjari, Alexander B. Voitkiv, M. Gundmundsson, Manfred Grieser, Claude Krantz, Michael Lestinsky, Andreas R. Wolf, Siegbert Hagmann, Robert Moshammer, Joachim Hermann Ullrich, Daniel Fischer Feb 2018

Mutual Projectile And Target Ionization In 1-Mev/Amu N4+ And N5++ He Collisions, Xincheng Wang, Katharina R. Schneider, Aditya H. Kelkar, Gunterschul Brenner, Michael Schulz, B. Najjari, Alexander B. Voitkiv, M. Gundmundsson, Manfred Grieser, Claude Krantz, Michael Lestinsky, Andreas R. Wolf, Siegbert Hagmann, Robert Moshammer, Joachim Hermann Ullrich, Daniel Fischer

Michael Schulz

We have studied mutual projectile and target ionization in 1-MeV/amu N4+ and N5++He collisions in kinematically complete experiments by measuring the momenta of the recoil ion and both ejected electrons in coincidence with the charge-changed projectiles. By means of four-particle Dalitz plots, in which multiple differential cross sections are presented as a function of the momenta of all four particles, experimental spectra are compared with theoretical results from various models. The experimental data are qualitatively reproduced by higher-order calculations, where good agreement is achieved for N5++He collisions, while some discrepancies persist for N4 ...


Investigating Two-Photon Double Ionization Of D2 By Xuv-Pump-Xuv-Probe Experiments, Yuhai Jiang, Artem Rudenko, Jhon Fredy Perez-Torres, Oliver Herrwerth, Lutz M. Foucar, Moritz Kurka, Kai Uwe Kuhnel, M. Toppin, Etienne Plesiat, Felipe Morales, Fernando Javier Martin, Matthias Lezius, Matthias F. Kling, Till Jahnke, Reinhard Dorner, Jose Luis Sanz-Vicario, Jeroen Van Tilborg, Ali Belkacem, Michael Schulz, Kiyoshi Ueda, Stefan Dusterer, Rolf Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich Feb 2018

Investigating Two-Photon Double Ionization Of D2 By Xuv-Pump-Xuv-Probe Experiments, Yuhai Jiang, Artem Rudenko, Jhon Fredy Perez-Torres, Oliver Herrwerth, Lutz M. Foucar, Moritz Kurka, Kai Uwe Kuhnel, M. Toppin, Etienne Plesiat, Felipe Morales, Fernando Javier Martin, Matthias Lezius, Matthias F. Kling, Till Jahnke, Reinhard Dorner, Jose Luis Sanz-Vicario, Jeroen Van Tilborg, Ali Belkacem, Michael Schulz, Kiyoshi Ueda, Stefan Dusterer, Rolf Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich

Michael Schulz

We used a split-mirror setup attached to a reaction microscope at the free-electron laser in Hamburg (FLASH) to perform an XUV-pump-XUV-probe experiment by tracing the ultrafast nuclear wave-packet motion in the D2 +(1sσg) with <10 fs time resolution. Comparison with time-dependent calculations shows excellent agreement with the measured vibrational period of 22±4 fs in D2+, points to the importance of accurately knowing the internuclear distance-dependent ionization probability, and paves the way to control sequential and nonsequential two-photon double-ionization contributions.


Observation Of Postcollision Effects In The Scattered Projectile Spectra For Ionizing Proton-Helium Collisions, Tibor Vajnai, A. D. Gaus, Joachim A. Brand, W. T. Htwe, Don H. Madison, Ronald E. Olson, Jerry Peacher, Michael Schulz Feb 2018

Observation Of Postcollision Effects In The Scattered Projectile Spectra For Ionizing Proton-Helium Collisions, Tibor Vajnai, A. D. Gaus, Joachim A. Brand, W. T. Htwe, Don H. Madison, Ronald E. Olson, Jerry Peacher, Michael Schulz

Michael Schulz

We have measured and calculated doubly differential single ionization cross sections as a function of the scattering angle and the projectile energy loss for 50 to 150 keV proton-helium collisions. These cross sections show unexpected structures as a function of both the energy loss and the scattering angle, which are interpreted as due to the postcollision interaction. Although the effects of postcollision interactions have previously been observed in electron spectra, this is the first observation of such effects for the scattered protons.


Manipulating Atomic Fragmentation Processes By Controlling The Projectile Coherence, Kisra N. Egodapitiya, Sachin D. Sharma, Ahmad Hasan, Aaron C. Laforge, Don H. Madison, Robert Moshammer, Michael Schulz Feb 2018

Manipulating Atomic Fragmentation Processes By Controlling The Projectile Coherence, Kisra N. Egodapitiya, Sachin D. Sharma, Ahmad Hasan, Aaron C. Laforge, Don H. Madison, Robert Moshammer, Michael Schulz

Michael Schulz

We have measured the scattering angle dependence of cross sections for ionization in p+H2 collisions for a fixed projectile energy loss. Depending on the projectile coherence, interference due to indistinguishable diffraction of the projectile from the two atomic centers was either present or absent in the data. This shows that, due to the fundamentals of quantum mechanics, the preparation of the beam must be included in theoretical calculations. The results have far-reaching implications on formal atomic scattering theory because this critical aspect has been overlooked for several decades.


Fully Differential Cusp Electron Production Cross Sections For 75-Kev H2+ + He Collisions, L. An, Kh Khayvat, Michael Schulz Feb 2018

Fully Differential Cusp Electron Production Cross Sections For 75-Kev H2+ + He Collisions, L. An, Kh Khayvat, Michael Schulz

Michael Schulz

A kinematically complete experiment on single ionization for 75-keV H2+ + H e collisions was performed by measuring the fully momentum analyzed projectiles and recoil ions in coincidence. The electron momentum was deduced from momentum conservation. Clear signatures of the postcollision interaction between the outgoing projectiles and the electrons were observed in the momentum spectra of all collision products simultaneously.