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 Impact Ionization (14)
 Ionization (9)
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 Electron ImpactIonization (5)
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Articles 1  30 of 44
FullText Articles in Physical Sciences and Mathematics
Quantum Critical Behavior Of The SuperfluidMott Glass Transition, Thomas Vojta, Jack Crewse, Martin Puschmann, Daniel Arovas, Yury Kiselev
Quantum Critical Behavior Of The SuperfluidMott Glass Transition, Thomas Vojta, Jack Crewse, Martin Puschmann, Daniel Arovas, Yury Kiselev
Physics Faculty Research & Creative Works
We investigate the zerotemperature superfluid to insulator transitions in a diluted twodimensional quantum rotor model with particlehole symmetry. We map the Hamiltonian onto a classical (2+1)dimensional XY model with columnar disorder which we analyze by means of largescale Monte Carlo simulations. For dilutions below the lattice percolation threshold, the system undergoes a generic superfluidMott glass transition. In contrast to other quantum phase transitions in disordered systems, its critical behavior is of conventional powerlaw type with universal (dilutionindependent) critical exponents z=1.52(3), ν =1.16(5), ß/ν =0.48(2), γ/ν=2.52(4), and ...
Comparison Of Experimental And Theoretical Fully Differential Cross Sections For Single Ionization Of The 2s And 2p States Of Li By O⁸⁺ Ions, Ebrahim GhanbariAdivi, Daniel Fischer, Natalia Ferreira, Johannes Goullon, Renate Hubele, Aaron Laforge, Michael Schulz, Don H. Madison
Comparison Of Experimental And Theoretical Fully Differential Cross Sections For Single Ionization Of The 2s And 2p States Of Li By O⁸⁺ Ions, Ebrahim GhanbariAdivi, Daniel Fischer, Natalia Ferreira, Johannes Goullon, Renate Hubele, Aaron Laforge, Michael Schulz, Don H. Madison
Physics Faculty Research & Creative Works
This paper presents a full threedimensional (3D) comparison between experiment and theory for 24 MeV O^{8+} single ionization of the 2s ground state of lithium and the 2p excited state. Two theoretical approximations are examined: the threebody continuum distortedwave (3DW) and threebody continuum distortedwaveeikonal initial state (3DWEIS). Normally, there is a significant difference between these two approaches and the 3DWEIS is in much better agreement with experiment. In this case, there is very little difference between the two approaches and both are in very good agreement with experiment. For the excited 2p state, the 3D cross sections would exhibit ...
Contact Process With Temporal Disorder, Hatem Barghathi, Thomas Vojta, José A. Hoyos
Contact Process With Temporal Disorder, Hatem Barghathi, Thomas Vojta, José A. Hoyos
Physics Faculty Research & Creative Works
We investigate the influence of timevarying environmental noise, i.e., temporal disorder, on the nonequilibrium phase transition of the contact process. Combining a realtime renormalization group, scaling theory, and large scale MonteCarlo simulations in one and two dimensions, we show that the temporal disorder gives rise to an exotic critical point. At criticality, the effective noise amplitude diverges with increasing time scale, and the probability distribution of the density becomes infinitely broad, even on a logarithmic scale. Moreover, the average density and survival probability decay only logarithmically with time. This infinitenoise critical behavior can be understood as the temporal counterpart ...
Multiple Fermi Surfaces In Superconducting NbDoped Bi₂Se₃, B. J. Lawson, Paul Corbae, Gang Li, Fan Yu, Tomoya Asaba, Colin Tinsman, Y. Qiu, Julia E. Medvedeva, Yew San Hor, L. Li
Multiple Fermi Surfaces In Superconducting NbDoped Bi₂Se₃, B. J. Lawson, Paul Corbae, Gang Li, Fan Yu, Tomoya Asaba, Colin Tinsman, Y. Qiu, Julia E. Medvedeva, Yew San Hor, L. Li
Physics Faculty Research & Creative Works
Topological insulator Bi_{2}Se_{3} has shown a number of interesting physical properties. Doping Bi_{2}Se_{3} with copper or strontium has been demonstrated to make the material superconducting and potentially even a topological superconductor. The recent discovery of superconducting niobiumdoped Bi_{2}Se_{3} reveals an exciting new physical phenomenon, the coexistence of superconductivity and magnetic ordering, as well as signatures of an oddparity pwave superconducting order. To understand this new phenomenon, a detailed knowledge of the electronic structure is needed. We present an observation of quantum oscillations in the magnetization (the de Haasvan Alphen effect) of ...
Kinematically Complete Study Of LowEnergy ElectronImpact Ionization Of Argon: Internormalized Cross Sections In ThreeDimensional Kinematics, Xueguang Ren, Sadek Amami, Oleg Zatsarinny, Thomas Pflüger, Marvin Weyland, Alexander Dorn, Don H. Madison, Klaus Bartschat
Kinematically Complete Study Of LowEnergy ElectronImpact Ionization Of Argon: Internormalized Cross Sections In ThreeDimensional Kinematics, Xueguang Ren, Sadek Amami, Oleg Zatsarinny, Thomas Pflüger, Marvin Weyland, Alexander Dorn, Don H. Madison, Klaus Bartschat
Physics Faculty Research & Creative Works
As a further test of advanced theoretical methods to describe electronimpact singleionization processes in complex atomic targets, we extended our recent work on Ne(2p) ionization [X. Ren, S. Amami, O. Zatsarinny, T. Pflüger, M. Weyland, W. Y. Baek, H. Rabus, K. Bartschat, D. Madison, and A. Dorn, Phys. Rev. A 91, 032707 (2015)PLRAAN1050294710.1103/PhysRevA.91.032707] to Ar(3p) ionization at the relatively low incident energy of E_{0} = 66 eV. The experimental data were obtained with a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission. We present experimental ...
Comparison Of Experimental And Theoretical Triple Differential Cross Sections For The Single Ionization Of Co₂ (1Πg) By Electron Impact, Zehra N. Ozer, Esam Ali, Mevlut Dogan, Murat Yavuz, Osman Alwan, Adnan Naja, Ochbadrakh Chuluunbaatar, Boghos B. Joulakian, ChuanGang Ning, James Colgan, Don H. Madison
Comparison Of Experimental And Theoretical Triple Differential Cross Sections For The Single Ionization Of Co₂ (1Πg) By Electron Impact, Zehra N. Ozer, Esam Ali, Mevlut Dogan, Murat Yavuz, Osman Alwan, Adnan Naja, Ochbadrakh Chuluunbaatar, Boghos B. Joulakian, ChuanGang Ning, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
Experimental and theoretical triple differential cross sections for intermediateenergy (250 eV) electronimpact single ionization of the CO_{2} are presented for three fixed projectile scattering angles. Results are presented for ionization of the outermost 1πg molecular orbital of CO_{2} in a coplanar asymmetric geometry. The experimental data are compared to predictions from the threecenter Coulomb continuum approximation for triatomic targets, and the molecular threebody distorted wave (M3DW) model. It is observed that while both theories are in reasonable qualitative agreement with experiment, the M3DW is in the best overall agreement with experiment.
Experimental And Theoretical TripleDifferential Cross Sections For Tetrahydrofuran Ionized By LowEnergy 26EvElectron Impact, Esam Ali, Xueguang Ren, Alexander Dorn, Chuangang Ning, James Colgan, Don H. Madison
Experimental And Theoretical TripleDifferential Cross Sections For Tetrahydrofuran Ionized By LowEnergy 26EvElectron Impact, Esam Ali, Xueguang Ren, Alexander Dorn, Chuangang Ning, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
We report an experimental and theoretical study of lowenergy electronimpact ionization of tetrahydrofuran, which is a molecule of biological interest. The experiments were performed using an advanced reaction microscope specially built for electronimpact ionization studies. The theoretical calculations were performed within the molecular threebody distortedwave model. Reasonably good agreement is found between experiment and theory.
Reply To "Comment On 'Classical Description Of H(1s) And H* (N=2) For CrossSection Calculations Relevant To ChargeExchange Diagnostics'", N. D. Cariatore, Sebastian Otranto, Ronald E. Olson
Reply To "Comment On 'Classical Description Of H(1s) And H* (N=2) For CrossSection Calculations Relevant To ChargeExchange Diagnostics'", N. D. Cariatore, Sebastian Otranto, Ronald E. Olson
Physics Faculty Research & Creative Works
In reply to the Comment of Jorge et al. [Phys. Rev. A 93, 066701 (2016)], we agree and reconfirm that the alternative classical trajectory Monte Carlo method (called hydrogenicZCTMC) radial distributions for H*(n = 2) we recently published are not stable in time. However, we show that such lack of stability which is more noticeable for H(2s) than for H(2p) is due to the initialization procedure employed and not to the hydrogenicZCTMC method itself. A new set of completely stable hydrogenicZCTMC calculations for H*(n = 2) is introduced and found in very good agreement with standard microcanonical results ...
SpatioTemporal Generalization Of The Harris Criterion And Its Application To Diffusive Disorder, Thomas Vojta, Ronald Dickman
SpatioTemporal Generalization Of The Harris Criterion And Its Application To Diffusive Disorder, Thomas Vojta, Ronald Dickman
Physics Faculty Research & Creative Works
We investigate how a clean continuous phase transition is affected by spatiotemporal disorder, i.e., by an external perturbation that fluctuates in both space and time. We derive a generalization of the Harris criterion for the stability of the clean critical behavior in terms of the spacetime correlation function of the external perturbation. As an application, we consider diffusive disorder, i.e., an external perturbation governed by diffusive dynamics, and its effects on a variety of equilibrium and nonequilibrium critical points. We also discuss the relation between diffusive disorder and diffusive dynamical degrees of freedom in the example of model ...
Random Field Disorder At An Absorbing State Transition In One And Two Dimensions, Hatem Barghathi, Thomas Vojta
Random Field Disorder At An Absorbing State Transition In One And Two Dimensions, Hatem Barghathi, Thomas Vojta
Physics Faculty Research & Creative Works
We investigate the behavior of nonequilibrium phase transitions under the influence of disorder that locally breaks the symmetry between two symmetrical macroscopic absorbing states. In equilibrium systems such "randomfield" disorder destroys the phase transition in low dimensions by preventing spontaneous symmetry breaking. In contrast, we show here that randomfield disorder fails to destroy the nonequilibrium phase transition of the one and twodimensional generalized contact process. Instead, it modifies the dynamics in the symmetrybroken phase. Specifically, the dynamics in the onedimensional case is described by a Sinai walk of the domain walls between two different absorbing states. In the twodimensional case ...
Role Of Composition And Structure On The Properties Of Metal/Multifunctional Ceramic Interfaces, Fang Yin Lin, Aleksandr V. Chernatynskiy, Juan Claudio Nino, Jacob L. Jones, Richard G. Hennig, Susan Sinnott
Role Of Composition And Structure On The Properties Of Metal/Multifunctional Ceramic Interfaces, Fang Yin Lin, Aleksandr V. Chernatynskiy, Juan Claudio Nino, Jacob L. Jones, Richard G. Hennig, Susan Sinnott
Physics Faculty Research & Creative Works
The formation of intermetallic secondary phases, such as Pt_{3}Pb, has been observed experimentally at PbTiO_{3}/Pt and Pb(Zr,Ti)O_{3}/Pt, or PZT/Pt, interfaces. Density functional theory calculations are used here to calculate the work of adhesion of these interfacial systems with and without the secondary intermetallic phase. The charge density maps of the interfaces reveal the electronic interactions at the interface and the impact of the secondary phase. In addition, Bader charge analysis provides a quantitative assessment of electron transfer from the perovskites to the Pt. Analysis of the band diagrams indicates an ...
Electron Impact Ionization Dynamics Of ParaBenzoquinone, D. B. Jones, E. Ali, C. G. Ning, J. Colgan, O. Ingólfsson, Don H. Madison, M. J. Brunger
Electron Impact Ionization Dynamics Of ParaBenzoquinone, D. B. Jones, E. Ali, C. G. Ning, J. Colgan, O. Ingólfsson, Don H. Madison, M. J. Brunger
Physics Faculty Research & Creative Works
Triple differential cross sections (TDCSs) for the electron impact ionization of the unresolved combination of the 4 highest occupied molecular orbitals (4b_{3g}, 5b_{2u}, 1b_{1g}, and 2b_{3u}) of parabenzoquinone are reported. These were obtained in an asymmetric coplanar geometry with the scattered electron being observed at the angles −7.5°, −10.0°, −12.5° and −15.0°. The experimental cross sections are compared to theoretical calculations performed at the molecular 3body distorted wave level, with a marginal level of agreement between them being found. The character of the ionized orbitals, through calculated momentum profiles, provides some qualitative ...
InfiniteNoise Criticality: Nonequilibrium Phase Transitions In Fluctuating Environments, Thomas Vojta, José A. Hoyos
InfiniteNoise Criticality: Nonequilibrium Phase Transitions In Fluctuating Environments, Thomas Vojta, José A. Hoyos
Physics Faculty Research & Creative Works
We study the effects of timevarying environmental noise on nonequilibrium phase transitions in spreading and growth processes. Using the examples of the logistic evolution equation as well as the contact process, we show that such temporal disorder gives rise to a distinct type of critical points at which the effective noise amplitude diverges on long time scales. This leads to enormous density fluctuations characterized by an infinitely broad probability distribution at criticality. We develop a realtime renormalizationgroup theory that provides a general framework for the effects of temporal disorder on nonequilibrium processes. We also discuss how general this exotic critical ...
Comparison Of Experimental And Theoretical ElectronImpactIonization TripleDifferential Cross Sections For Ethane, Esam Ali, Kate Nixon, Andrw Murray, Chuangang Ning, James Colgan, Don H. Madison
Comparison Of Experimental And Theoretical ElectronImpactIonization TripleDifferential Cross Sections For Ethane, Esam Ali, Kate Nixon, Andrw Murray, Chuangang Ning, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
We have recently examined electronimpact ionization of molecules that have one large atom at the center, surrounded by H nuclei (H_{2}O, NH_{3}, CH_{4}). All of these molecules have ten electrons; however, they vary in their molecular symmetry. We found that the tripledifferential cross sections (TDCSs) for the highest occupied molecular orbitals (HOMOs) were similar, as was the character of the HOMO orbitals which had a ptype "peanut" shape. In this work, we examine ethane (C_{2}H_{6}) which is a molecule that has two large atoms surrounded by H nuclei, so that its HOMO has ...
Evidence For UnnaturalParity Contributions To ElectronImpact Ionization Of LaserAligned Atoms, G. S. J. Armstrong, J. Colgan, M. S. Pindzola, S. Amami, Don H. Madison, J. Pursehouse, K. L. Nixon, A. J. Murray
Evidence For UnnaturalParity Contributions To ElectronImpact Ionization Of LaserAligned Atoms, G. S. J. Armstrong, J. Colgan, M. S. Pindzola, S. Amami, Don H. Madison, J. Pursehouse, K. L. Nixon, A. J. Murray
Physics Faculty Research & Creative Works
Recent measurements have examined the electronimpact ionization of excitedstate laseraligned Mg atoms. In this work we show that the ionization cross section arising from the geometry where the aligned atom is perpendicular to the scattering plane directly probes the unnatural parity contributions to the ionization amplitude. The contributions from natural parity partial waves cancel exactly in this geometry. Our calculations resolve the discrepancy between the nonzero measured cross sections in this plane and the zero cross section predicted by distortedwave approaches. We demonstrate that this is a general feature of ionization from pstate targets by additional studies of ionization from ...
Anharmonic Properties In Mg₂X (X= C, Si, Ge, Sn, Pb) From FirstPrinciples Calculations, Aleksandr V. Chernatynskiy, Simon R. Phillpot
Anharmonic Properties In Mg₂X (X= C, Si, Ge, Sn, Pb) From FirstPrinciples Calculations, Aleksandr V. Chernatynskiy, Simon R. Phillpot
Physics Faculty Research & Creative Works
Thermal conductivity reduction is one of the potential routes to improve the performance of thermoelectric materials. However, detailed understanding of the thermal transport of many promising materials is still missing. In this paper, we employ electronicstructure calculations at the level of density functional theory to elucidate thermal transport properties of the Mg_{2}X (X=C, Si, Ge, Sn, and Pb) family of compounds, which includes Mg_{2}Si, a material already identified as a potential thermoelectric. All these materials crystallize into the same antifluorite structure. Systematic trends in the anharmonic properties of these materials are presented and examined. Our ...
Interference Effects For Intermediate Energy ElectronImpact Ionization Of H₂ And N₂ Molecules, Zehra Nur Ozer, Hari Chaluvadi, Don H. Madison, Mevlut Dogan
Interference Effects For Intermediate Energy ElectronImpact 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 H_{2} and N_{2} 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 electronimpact ionization. The experimental measurements are performed using a crossedbeamtype electronelectron coincidence spectrometer and theoretical calculations are obtained using the Molecular Three Body Distorted Wave Approximation (M3DW). We found that the Ifactor demonstrated strong evidence for twocenter interference effects for both H_{2} and N_{2}. We also found that the Ifactor is more sensitive to projectile angular scans than ...
Emerging Criticality In The Disordered ThreeColor AshkinTeller Model, Qiong Zhu, Xin Wan, Rajesh Narayanan, José A. Hoyos, Thomas Vojta
Emerging Criticality In The Disordered ThreeColor AshkinTeller Model, Qiong Zhu, Xin Wan, Rajesh Narayanan, José A. Hoyos, Thomas Vojta
Physics Faculty Research & Creative Works
We study the effects of quenched disorder on the firstorder phase transition in the twodimensional threecolor AshkinTeller model by means of largescale Monte Carlo simulations. We demonstrate that the firstorder phase transition is rounded by the disorder and turns into a continuous one. Using a careful finitesizescaling analysis, we provide strong evidence for the emerging critical behavior of the disordered AshkinTeller model to be in the clean twodimensional Ising universality class, accompanied by universal logarithmic corrections. This agrees with perturbative renormalizationgroup predictions by Cardy. As a byproduct, we also provide support for the stronguniversality scenario for the critical behavior of ...
Erratum: Theoretical And Experimental (E,2e) Study Of ElectronImpact Ionization Of LaserAligned Mg Atoms [Physical Review A 90, 062707 (2014)], Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison
Erratum: Theoretical And Experimental (E,2e) Study Of ElectronImpact Ionization Of LaserAligned Mg Atoms [Physical Review A 90, 062707 (2014)], Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
We have recently reported a theoretical and experimental study of electronimpact ionization of laseraligned magnesium. Results were presented for both ionization of the ground state, as well as for laseraligned atoms in the 3p state. For ionization from the 3p state, theoretical results were presented using the distorted wave Born (DWBA) and threebody distorted wave (3DW) approximations. Unfortunately, after publication we learned that the theoretical results were incorrect due to one of the arrays in the computer code dimensioned too small. The figures affected by this error are Figs. 3–5 in the original paper. The present Figs ...
Classical Description Of H(1s) And H* (N=2) For CrossSection Calculations Relevant To ChargeExchange Diagnostics, N. D. Cariatore, Sebastian Otranto, Ronald E. Olson
Classical Description Of H(1s) And H* (N=2) For CrossSection Calculations Relevant To ChargeExchange Diagnostics, N. D. Cariatore, Sebastian Otranto, Ronald E. Olson
Physics Faculty Research & Creative Works
In this work, we introduce a classical trajectory Monte Carlo (CTMC) methodology, specially conceived to provide a more accurate representation of chargeexchange processes between highly charged ions and H(1s) and H* (n=2). These processes are of particular relevance in power fusion reactor programs, for which chargeexchange spectroscopy has become a useful plasma diagnostics tool. To test the methodology, electroncapture reactions from these targets by C^{6+},N^{7+}, and O^{8+} are studied at impact energies in the 10150keV/amu range. Stateselective cross sections are contrasted with those predicted by the standard microcanonical formulation of the CTMC method ...
Kinematically Complete Study Of LowEnergy ElectronImpact Ionization Of Neon: Internormalized Cross Sections In ThreeDimensional Kinematics, Xueguang Ren, Sadek Amami, Oleg Zatsarinny, Thomas Pflüger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn
Kinematically Complete Study Of LowEnergy ElectronImpact Ionization Of Neon: Internormalized Cross Sections In ThreeDimensional Kinematics, Xueguang Ren, Sadek Amami, Oleg Zatsarinny, Thomas Pflüger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Klaus Bartschat, Don H. Madison, Alexander Dorn
Physics Faculty Research & Creative Works
Lowenergy (E_{0} 0=65eV) electronimpact single ionization of Ne (2p) has been investigated to thoroughly test stateoftheart theoretical approaches. The experimental data were measured using a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission energies ranging from 2 to 8 eV, and projectile scattering angles ranging from 8.5⁰ to 20.0⁰. The experimental tripledifferential cross sections are internormalized across all measured scattering angles and ejected energies. The experimental data are compared to predictions from a hybrid secondorder distortedwave Born plus Rmatrix approach, the distortedwave Born approximation with the inclusion of ...
Electron And PhotonImpact Ionization Of Furfural, D. B. Jones, E. Ali, K. L. Nixon, P. LimãoVieira, M.J. HubinFranskin, J. Delwiche, C. G. Ning, J. Colgan, Andrew J. Murray, Don H. Madison, M .J. Brunger
Electron And PhotonImpact Ionization Of Furfural, D. B. Jones, E. Ali, K. L. Nixon, P. LimãoVieira, M.J. HubinFranskin, J. Delwiche, C. G. Ning, J. Colgan, Andrew J. Murray, Don H. Madison, M .J. Brunger
Physics Faculty Research & Creative Works
The He(i) photoelectron spectrum of furfural has been investigated, with its vibrational structure assigned for the first time. The ground and excited ionized states are assigned through ab initio calculations performed at the outervalence Green's function level. Triple differential cross sections (TDCSs) for electronimpact ionization of the unresolved combination of the 4a" + 21a' highest and nexthighest occupied molecular orbitals have also been obtained. Experimental TDCSs are recorded in a combination of asymmetric coplanar and doubly symmetric coplanar kinematics. The experimental TDCSs are compared to theoretical calculations, obtained within a molecular 3body distorted wave framework that employed either an ...
Computational Discovery Of Lanthanide Doped And CoDoped Y₃Al₅O₁₂ For Optoelectronic Applications, Kamal Kumar Choudhary, Aleksandr V. Chernatynskiy, Kiran Mathew, Eric W. Bucholz, Simon R. Phillpot, Susan Sinnott, Richard G. Hennig
Computational Discovery Of Lanthanide Doped And CoDoped Y₃Al₅O₁₂ For Optoelectronic Applications, Kamal Kumar Choudhary, Aleksandr V. Chernatynskiy, Kiran Mathew, Eric W. Bucholz, Simon R. Phillpot, Susan Sinnott, Richard G. Hennig
Physics Faculty Research & Creative Works
We systematically elucidate the optoelectronic properties of rareearth doped and Ce codoped yttrium aluminum garnet (YAG) using hybrid exchangecorrelation functional based density functional theory. The predicted optical transitions agree with the experimental observations for single doped Ce:YAG, Pr:YAG, and codoped Er,Ce:YAG. We find that codoping of Cedoped YAG with any lanthanide except Eu and Lu lowers the transition energies; we attribute this behavior to the lanthanideinduced change in bonding environment of the dopant atoms. Furthermore, we find infrared transitions only in case of the Er, Tb, and Tm codoped Ce:YAG and suggest Tm,Ce:YAG ...
CompositionDependent Structural And Transport Properties Of Amorphous Transparent Conducting Oxides, Rabi Khanal, D. Bruce Buchholz, Robert P. Chang, Julia E. Medvedeva
CompositionDependent Structural And Transport Properties Of Amorphous Transparent Conducting Oxides, Rabi Khanal, D. Bruce Buchholz, Robert P. Chang, Julia E. Medvedeva
Physics Faculty Research & Creative Works
Structural properties of amorphous Inbased oxides, InXO with X=Zn, Ga, Sn, or Ge, are investigated using ab initio molecular dynamics liquidquench simulations. The results reveal that indium retains its average coordination of 5.0 upon 20% X fractional substitution for In, whereas X cations satisfy their natural coordination with oxygen atoms. This finding suggests that the carrier generation is primarily governed by In atoms, in accord with the observed carrier concentration in amorphous InO and InXO. At the same time, the presence of X affects the number of sixcoordinated In atoms as well as the oxygen sharing between the ...
XRay Emission Produced In ChargeExchange Collisions Between Highly Charged Ions And Argon: Role Of The Multiple Electron Capture, Sebastian Otranto, N. D. Cariatore, Ronald E. Olson
XRay Emission Produced In ChargeExchange Collisions Between Highly Charged Ions And Argon: Role Of The Multiple Electron Capture, Sebastian Otranto, N. D. Cariatore, Ronald E. Olson
Physics Faculty Research & Creative Works
In this work we use the classical trajectory Monte Carlo method within an eightelectron scheme to theoretically study photonic spectra that follow chargeexchange processes between highly charged ions of charge states 10+, 17+, 18+, and 36+ with neutral argon. The energy range considered is 18 eV/amu to 4 keV/amu, covering typical electron beam ion traps and solar wind energies. The role played by multiple electron capture processes for the different collision systems under consideration is explicitly analyzed and its contribution separated as arising from radiative decay and autoionizing multiple capture. For the present collision systems we find that ...
Theoretical And Experimental (E, 2e) Study Of ElectronImpact Ionization Of LaserAligned Mg Atoms, Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison
Theoretical And Experimental (E, 2e) Study Of ElectronImpact Ionization Of LaserAligned Mg Atoms, Sadek Amami, Andrew J. Murray, Al Stauffer, Kate Nixon, Gregory Armstrong, James Colgan, Don H. Madison
Physics Faculty Research & Creative Works
We have performed calculations of the fully differential cross sections for electronimpact ionization of magnesium atoms. Three theoretical approximations, the timedependent close coupling, the threebody distorted wave, and the distorted wave Born approximation, are compared with experiment in this article. Results will be shown for ionization of the 3s ground state of Mg for both asymmetric and symmetric coplanar geometries. Results will also be shown for ionization of the 3p state which has been excited by a linearly polarized laser which produces a charge cloud aligned perpendicular to the laser beam direction and parallel to the linear polarization. Theoretical and ...
Enhanced RareRegion Effects In The Contact Process With LongRange Correlated Disorder, Ahmed K. Ibrahim, Hatem Barghathi, Thomas Vojta
Enhanced RareRegion Effects In The Contact Process With LongRange Correlated Disorder, Ahmed K. Ibrahim, Hatem Barghathi, Thomas Vojta
Physics Faculty Research & Creative Works
We investigate the nonequilibrium phase transition in the disordered contact process in the presence of longrange spatial disorder correlations. These correlations greatly increase the probability for finding rare regions that are locally in the active phase while the bulk system is still in the inactive phase. Specifically, if the correlations decay as a power of the distance, the rareregion probability is a stretched exponential of the rareregion size rather than a simple exponential as is the case for uncorrelated disorder. As a result, the Griffiths singularities are enhanced and take a nonpowerlaw form. The critical point itself is of infiniterandomness ...
Phase Transitions On Random Lattices: How Random Is Topological Disorder?, Hatem Barghathi, Thomas Vojta
Phase Transitions On Random Lattices: How Random Is Topological Disorder?, Hatem Barghathi, Thomas Vojta
Physics Faculty Research & Creative Works
We study the effects of topological (connectivity) disorder on phase transitions. We identify a broad class of random lattices whose disorder fluctuations decay much faster with increasing length scale than those of generic random systems, yielding a wandering exponent of ω = (d−1)/(2d) in d dimensions. The stability of clean critical points is thus governed by the criterion (d+1)ν > 2 rather than the usual Harris criterion dν > 2, making topological disorder less relevant than generic randomness. The ImryMa criterion is also modified, allowing firstorder transitions to survive in all dimensions d > 1. These results explain a host ...
StrongDisorder Magnetic Quantum Phase Transitions: Status And New Developments, Thomas Vojta
StrongDisorder Magnetic Quantum Phase Transitions: Status And New Developments, Thomas Vojta
Physics Faculty Research & Creative Works
This article reviews the unconventional effects of random disorder on magnetic quantum phase transitions, focusing on a number of new experimental and theoretical developments during the last three years. On the theory side, we address smeared quantum phase transitions tuned by changing the chemical composition, for example in alloys of the type A_{1x}B_{x}. We also discuss how the interplay of order parameter conservation and overdamped dynamics leads to enhanced quantum Griffiths singularities in disordered metallic ferromagnets. Finally, we discuss a semiclassical theory of transport properties in quantum Griffiths phases. Experimental examples include the ruthenates Sr_{1x}Ca ...
Effect Of The CenterOfMass Approximation On The Scaling Of ElectronCapture Fully Differential Cross Sections, A. L. Harris, Don H. Madison
Effect Of The CenterOfMass Approximation On The Scaling Of ElectronCapture Fully Differential Cross Sections, A. L. Harris, Don H. Madison
Physics Faculty Research & Creative Works
We present results for p+He single electron capture and transfer with target excitation using the first Born approximation. The effect of approximating the center of mass of the helium atom and outgoing hydrogen atom at the respective nuclei is explored. Semianalytical results are compared for the calculations with and without the approximation, and it is shown that one must properly account for the center of mass of the atoms. It is also shown that this approximation is the result of the apparent v^{4} scaling that was previously observed with the fourbody transfer with target excitation model.