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Full-Text Articles in Physical Sciences and Mathematics
Interference Effects For Intermediate Energy Electron-Impact Ionization Of H₂ And N₂ Molecules, Zehra Nur Ozer, Hari Chaluvadi, Don H. Madison, Mevlut Dogan
Interference Effects For Intermediate Energy Electron-Impact Ionization Of H₂ And N₂ Molecules, Zehra Nur Ozer, Hari Chaluvadi, Don H. Madison, Mevlut Dogan
Physics Faculty Research & Creative Works
We have studied electron impact ionization of H2 and N2 molecules at intermediate energies to look for possible two center interference effects experimentally and theoretically. Here we report a study of the interference factor I for 250 eV electron-impact ionization. The experimental measurements are performed using a crossed-beam-type electron-electron coincidence spectrometer and theoretical calculations are obtained using the Molecular Three Body Distorted Wave Approximation (M3DW). We found that the I-factor demonstrated strong evidence for two-center interference effects for both H2 and N2. We also found that the I-factor is more sensitive to projectile angular scans …
Complete Momentum Balance In Ionization Of H₂ By 75-Kev-Proton Impact For Varying Projectile Coherence, Sachin D. Sharma, T. P. Arthanayaka, Ahmad Hasan, B. R. Lamichhane, J. Remolina, Adolph P. Smith, Michael Schulz
Complete Momentum Balance In Ionization Of H₂ By 75-Kev-Proton Impact For Varying Projectile Coherence, Sachin D. Sharma, T. P. Arthanayaka, Ahmad Hasan, B. R. Lamichhane, J. Remolina, Adolph P. Smith, Michael Schulz
Physics Faculty Research & Creative Works
We report on a kinematically complete experiment on ionization of H2 by proton impact. While a significant impact of the projectile coherence properties on the scattering-angle dependence of double-differential cross sections (DDCSs), reported earlier, is confirmed by the present data, only weak coherence effects are found in the electron and recoil-ion momentum dependence of the DDCSs. This suggests that the phase angle in the interference term is determined primarily by the projectile momentum transfer rather than by the recoil-ion momentum. We therefore cannot rule out the possibility that the interference observed in our data is not primarily due to …
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
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
Physics Faculty Research & Creative Works
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 calculations. …
Comment On "Singly Ionizing 100-Mev/Amu C⁶⁺+He Collisions With Small Momentum Transfer", Michael Schulz, Robert Moshammer, Daniel Fischer, Joachim Hermann Ullrich
Comment On "Singly Ionizing 100-Mev/Amu C⁶⁺+He Collisions With Small Momentum Transfer", Michael Schulz, Robert Moshammer, Daniel Fischer, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
In a recent article, Kouzakov suggested that experimental resolution effects can be responsible for discrepancies between measured and calculated fully differential cross sections for the ionization of helium by fast C6+ impact. They further asserted that projectile-coherence effects have no influence on the measured cross sections. In this Comment, we reiterate that the experimental resolution can only explain part of the discrepancies. Furthermore, we note that the conclusion regarding the role of projectile coherence neglects potential interference between first- and higher-order transition amplitudes.
Picturing Electron Capture To The Continuum In The Transfer Ionization Of Intermediate-Energy He²⁺ Collisions With Argon, Ruitian Zhang, Xinwen Ma, Shaofeng Zhang, Xiaolong Zhu, Susmitha Akula, Don H. Madison, Bingsheng Li, Dongbin Qian, Wentian Feng, Dalong Guo, Huiping Liu, Shuncheng Yan, Pengju Zhang, Shenyue Xu, Ximeng Chen
Picturing Electron Capture To The Continuum In The Transfer Ionization Of Intermediate-Energy He²⁺ Collisions With Argon, Ruitian Zhang, Xinwen Ma, Shaofeng Zhang, Xiaolong Zhu, Susmitha Akula, Don H. Madison, Bingsheng Li, Dongbin Qian, Wentian Feng, Dalong Guo, Huiping Liu, Shuncheng Yan, Pengju Zhang, Shenyue Xu, Ximeng Chen
Physics Faculty Research & Creative Works
Electron emission occurring in transfer ionization for He2+ collisions with argon has been investigated using cold target recoil ion momentum spectroscopy. The double differential cross sections for electron capture to the continuum of the projectile (cusp-shaped electrons) are presented for collision energies from 17.5 to 75 keV/u. For an energy of 30 keV/u, we find a maximum in the experimental ratio of the cusp-shaped electron yield to the total electron yield. This result is explained in terms of the velocity matching between the projectile ion and the electron initially bound to the target. One of the important issues for …
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
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
Physics Faculty Research & Creative Works
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.
Effect Of Projectile Coherence On Atomic Fragmentation Processes, Michael Schulz, Kisra N. Egodapitiya, Sachin D. Sharma, Aaron C. Laforge, Robert Moshammer, A. A. Hasan, Don H. Madison
Effect Of Projectile Coherence On Atomic Fragmentation Processes, Michael Schulz, Kisra N. Egodapitiya, Sachin D. Sharma, Aaron C. Laforge, Robert Moshammer, A. A. Hasan, Don H. Madison
Physics Faculty Research & Creative Works
We demonstrate that the projectile coherence can have a major impact on atomic fragmentation processes. This has been overlooked for decades in formal scattering theory and may explain puzzling discrepancies between theoretical and experimental fully differential cross sections for single ionization.
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
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
Physics Faculty Research & Creative Works
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++He …
Young-Type Interference In Projectile-Electron Loss In Energetic Ion-Molecule Collisions, Alexander B. Voitkiv, B. Najjari, Daniel Fischer, Anton N. Artemyev, Andrey S. Surzhykov
Young-Type Interference In Projectile-Electron Loss In Energetic Ion-Molecule Collisions, Alexander B. Voitkiv, B. Najjari, Daniel Fischer, Anton N. Artemyev, Andrey S. Surzhykov
Physics Faculty Research & Creative Works
Under certain conditions an electron bound in a fast projectile ion, colliding with a molecule, interacts mainly with the nuclei and inner shell electrons of atoms forming the molecule. Because of their compact localization in space and distinct separation from each other, these molecular centers play in such collisions a role similar to that of optical slits in light scattering leading to pronounced interference in the spectra of the electron emitted from the projectile.
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
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
Physics Faculty Research & Creative Works
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.
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
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
Physics Faculty Research & Creative Works
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.
Four-Body Model For Transfer Excitation, Allison L. Harris, Jerry Peacher, Don H. Madison, James Colgan
Four-Body Model For Transfer Excitation, Allison L. Harris, Jerry Peacher, Don H. Madison, James Colgan
Physics Faculty Research & Creative Works
We present here a four-body model for transfer-excitation collisions, which we call the four-body transfer-excitation (4BTE) model. Each two-body interaction is explicitly included in the 4BTE model, allowing us to study the effects of individual two-body interactions. We apply our model to fully differential cross sections for proton+helium collisions, and study the effect of the incident projectile-atom interaction, the scattered projectile-ion interaction, the projectile-nuclear interaction, and electron correlation within the target atom.
Light-Particle Single Ionization Of Argon: Influence Of The Projectile Charge Sign, Sebastian Otranto, Ronald E. Olson
Light-Particle Single Ionization Of Argon: Influence Of The Projectile Charge Sign, Sebastian Otranto, Ronald E. Olson
Physics Faculty Research & Creative Works
The ionization of the 3p orbital of argon by incident electrons and positrons is studied by means of the post version of the continuum distorted wave-eikonal initial-state model. Results are presented at both 200 and 500 eV impact energies for conditions amenable to present experiments. Differences in the fully differential cross sections (FDCSs) are analyzed and the influence of the projectile charge sign on the emission dynamics is discussed. The FDCSs are found to display the classic binary plus recoil peak structure at 500 eV, but transition to a more complicated four-lobed structure at the lower impact energy.
Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Ahmad Hasan, Michael Schulz, Aaron C. Laforge, Jason S. Alexander, M. F. Ciappina, M. A. Khakoo, Kisra Nayomal Egodapitiya
Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Ahmad Hasan, Michael Schulz, Aaron C. Laforge, Jason S. Alexander, M. F. Ciappina, M. A. Khakoo, Kisra Nayomal Egodapitiya
Physics Faculty Research & Creative Works
Doubly differential cross sections for single ionization of atomic hydrogen by 75 keV proton impact have been measured and calculated as a function of the projectile scattering angle and energy loss. This pure three-body collision system represents a fundamental test case for the study of the reaction dynamics in few-body systems. A comparison between theory and experiment reveals that three-body dynamics is important at all scattering angles and that an accurate description of the role of the projectile-target-nucleus interaction remains a major challenge to theory.
Triple-Differential Cross Sections For Target Ionization With Simultaneous Projectile Detachment In 200-Kev H⁻ + He Collisions, T. Ferger, Michael Schulz, Daniel Fischer, B. Najjari, R. Moshammer, J. D. Ullrich
Triple-Differential Cross Sections For Target Ionization With Simultaneous Projectile Detachment In 200-Kev H⁻ + He Collisions, T. Ferger, Michael Schulz, Daniel Fischer, B. Najjari, R. Moshammer, J. D. Ullrich
Physics Faculty Research & Creative Works
We have performed a kinematically complete experiment for target ionization with simultaneous projectile detachment (TIPD) in 200-keV H− + He collisions. From the data we extracted triple-differential cross sections (TDCSs) for each electron separately. These TDCSs closely resemble corresponding data for single ionization by charged-particle impact. Surprisingly, the contributions from higher-order processes to TIPD, proceeding through two independent interactions of each electron with the core of the respective other collision partner, are found to be somewhat larger than the first-order process proceeding through the electron-electron interaction.
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
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
Physics Faculty Research & Creative Works
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.