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Articles 1  25 of 25
FullText Articles in Physical Sciences and Mathematics
Charge Transfer In Slow Collisions Of C⁴⁺ With H Below 1 Kev/Amu, ChenNan Liu, AnhThu Le, C. D. Lin
Charge Transfer In Slow Collisions Of C⁴⁺ With H Below 1 Kev/Amu, ChenNan Liu, AnhThu Le, C. D. Lin
Physics Faculty Research & Creative Works
We reexamined chargetransfer cross sections for C⁴⁺ + H collisions for energies from 1 meV/amu to 1 keV/amu using the recently developed hyperspherical closecoupling method. Our results agree with several previous theoretical calculations using molecularorbital expansion. However, these converged theoretical predictions do not agree with total cross sections from the mergedbeam experiments.
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
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
Physics Faculty Research & Creative Works
Recently, threedimensional imaging of the ejected electrons following 100 MeV/amu C^{6+} 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 momentumtransfer axis, a ringshaped 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 multiplescattering ...
Lamb Shift Of LaserDressed Atomic States, Ulrich D. Jentschura, Jorg Evers, Martin K. Haas, Christoph H. Keitel
Lamb Shift Of LaserDressed Atomic States, Ulrich D. Jentschura, Jorg Evers, Martin K. Haas, Christoph H. Keitel
Physics Faculty Research & Creative Works
We discuss radiative corrections to an atomic twolevel system subject to an intense driving laser field. It is shown that the Lamb shift of the laserdressed states, which are the natural state basis of the combined atomlaser system, cannot be explained in terms of the Lamb shift received by the atomic bare states which is usually observed in spectroscopic experiments. In the final part, we propose an experimental scheme to measure these corrections based on the incoherent resonance fluorescence spectrum of the driven atom.
Statistics Of Transmission In OneDimensional Disordered Systems: Universal Characteristics Of States In The Fluctuation Tails, Lev I. Deych, Mikhail V. Erementchouk, Alexander A. Lisyansky, Alexey Yamilov, Hui Cao
Statistics Of Transmission In OneDimensional Disordered Systems: Universal Characteristics Of States In The Fluctuation Tails, Lev I. Deych, Mikhail V. Erementchouk, Alexander A. Lisyansky, Alexey Yamilov, Hui Cao
Physics Faculty Research & Creative Works
We numerically study the distribution function of the conductance (transmission) in the onedimensional tightbinding Anderson and periodiconaverage superlattice models in the region of fluctuation states where single parameter scaling is not valid. We show that the scaling properties of the distribution function depend upon the relation between the system's length L and the length l_{s} determined by the integral density of states. For long enough systems, L ≫ l_{s}, the distribution can still be described within a new scaling approach based upon the ratio of the localization length l_{loc} and l_{s}. In an intermediate interval of ...
Resonant Photoemission In FElectron Systems: Pu And Gd, James G. Tobin, Brandon W. Chung, Roland K. Schulze, Jeff Russell Terry, John Douglas Farr, David K. Shuh, K. Heinzelman, Eli Rotenberg, George Daniel Waddill, Gerrit V. Van Der Laan
Resonant Photoemission In FElectron Systems: Pu And Gd, James G. Tobin, Brandon W. Chung, Roland K. Schulze, Jeff Russell Terry, John Douglas Farr, David K. Shuh, K. Heinzelman, Eli Rotenberg, George Daniel Waddill, Gerrit V. Van Der Laan
Physics Faculty Research & Creative Works
Resonant photoemission in the Pu 5f and Pu 6p states is compared to that in the Gd 4f and Gd 5p states. Spectral simulations, based upon an atomic model with angular momentum coupling, are compared to the Gd and Pu results. Additional spectroscopic measurements of Pu, including core level photoemission and xray absorption, are also presented.
Perturbation Approach To The SelfEnergy Of NonS Hydrogenic States, Eric Olivier Le Bigot, Ulrich D. Jentschura, Peter J. Mohr, Paul Indelicato, Gerhard Soff
Perturbation Approach To The SelfEnergy Of NonS Hydrogenic States, Eric Olivier Le Bigot, Ulrich D. Jentschura, Peter J. Mohr, Paul Indelicato, Gerhard Soff
Physics Faculty Research & Creative Works
We present results on the selfenergy correction to the energy levels of hydrogen and hydrogenlike ions. The self energy represents the largest QED correction to the relativistic (DiracCoulomb) energy of a bound electron. We focus on the perturbation expansion of the self energy of nonS states, and provide estimates of the socalled A_{60} perturbative coefficient, which can be considered as a relativistic Bethe logarithm. Precise values of A_{60} are given for many P, D, F and G states, while estimates are given for other electronic states. These results can be used in highprecision spectroscopy experiments in hydrogen and ...
Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia
Black Hole Multiplicity At Particle Colliders (Do Black Holes Radiate Mainly On The Brane?), Marco Cavaglia
Physics Faculty Research & Creative Works
If gravity becomes strong at the TeV scale, we may have the chance to produce black holes at particle colliders. In this Letter we revisit some phenomenological signatures of black hole production in TeVgravity theories. We show that the bulktobrane ratio of black hole energy loss during the Hawking evaporation phase depends crucially on the black hole greybody factors and on the particle degrees of freedom. Since the greybody factors have not yet been calculated in the literature, and the particle content at transPlanckian energies is not known, it is premature to claim that the black hole emits mainly on ...
TwoLoop BetheLogarithm Correction In Hydrogenlike Atoms, Krzysztof Pachucki, Ulrich D. Jentschura
TwoLoop BetheLogarithm Correction In Hydrogenlike Atoms, Krzysztof Pachucki, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We calculate the twoloop Bethe logarithm correction to atomic energy levels in hydrogenlike systems. The twoloop Bethe logarithm is a lowenergy quantum electrodynamic (QED) effect involving multiple summations over virtual excited atomic states. Although much smaller in absolute magnitude than the wellknown oneloop Bethe logarithm, the twoloop analog is quite significant when compared to the current experimental accuracy of the 1 S – 2 S transition: It contributes  8.19 and  0.84 k H z for the 1 S and the 2 S state, respectively. The twoloop Bethe logarithm has been the largest unknown correction to the hydrogen Lamb shift ...
Rescattering Of UltralowEnergy Electrons For Single Ionization Of Ne In The Tunneling Regime, Robert Moshammer, Joachim Hermann Ullrich, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, Jose R. Crespo LopezUrrutia, C. Hoehr, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner
Rescattering Of UltralowEnergy Electrons For Single Ionization Of Ne In The Tunneling Regime, Robert Moshammer, Joachim Hermann Ullrich, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, Jose R. Crespo LopezUrrutia, C. Hoehr, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner
Physics Faculty Research & Creative Works
Electron emission for single ionization of Ne by 25 fs, 1.0 PW/cm^{2} laser pulses at 800 nm was investigated. Kinematics was studied using a 'reaction microscope'. Results showed a zero longitudinal momentum of a lowenergy electron with high resolution.
Dynamic Nonlinear Effect On Lasing In A Random Medium, Boyang Liu, Alexey Yamilov, Yong Ling, Junying Xu, Hui Cao
Dynamic Nonlinear Effect On Lasing In A Random Medium, Boyang Liu, Alexey Yamilov, Yong Ling, Junying Xu, Hui Cao
Physics Faculty Research & Creative Works
We have studied both experimentally and numerically the dynamic effect of nonlinearity on lasing in disordered medium. The thirdorder nonlinearity not only changes the frequency and size of lasing modes, but also modifies the laser emission intensity and laser pulse width. When the nonlinear response time is longer than the lifetime of the lasing mode, the nonlinearity changes the laser output through modifying the size of the lasing mode. When the nonlinear response is faster than the buildup of the lasing mode, positive nonlinearity always extracts more laser emission from the random medium due to the enhancement of single particle ...
Density Of Resonant States And A Manifestation Of Photonic Band Structure In Small Clusters Of Spherical Particles, Alexey Yamilov, Hui Cao
Density Of Resonant States And A Manifestation Of Photonic Band Structure In Small Clusters Of Spherical Particles, Alexey Yamilov, Hui Cao
Physics Faculty Research & Creative Works
We introduce a numerical recipe for calculating the density of the resonant states of the clusters of dielectric spheres. Using truncated multipole expansions (generalized multisphere Mie solution) we obtain the scattering matrix of the problem. By introducing an infinitesimal absorption in the spheres we express the dwell time of the electromagnetic wave in terms of the elements of the scattering matrix. Using the parameters in recent light localization experiments [Phys. Rev. Lett. 87, 153901 (2001)], we demonstrate that the density of the resonant states, related to the dwell time, shows the formation of the photonic band structure in small clusters ...
Role Of The Ground State In ElectronAtom Double Ionization, Stephenie J. Jones, Don H. Madison
Role Of The Ground State In ElectronAtom Double Ionization, Stephenie J. Jones, Don H. Madison
Physics Faculty Research & Creative Works
Recently, absolute measurements have been reported for double ionization of helium by 5.6 keV electronimpact. At this high energy, one would think that the first Born approximation for the interaction of the projectile with the atom would be valid. However, on the basis of a lowestorder implementation of a Faddeevtype approach, Berakdar concluded that the approximation was not valid. Here we argue that (i) it is valid at this energy and (ii) the previous discrepancy between calculations in the first Born approximation and the overall magnitude of the measurements was due to a poor description of the ground state.
Effect Of Kerr Nonlinearity On Defect Lasing Modes In Weakly Disordered Photonic Crystals, Boyang Liu, Alexey Yamilov, Hui Cao
Effect Of Kerr Nonlinearity On Defect Lasing Modes In Weakly Disordered Photonic Crystals, Boyang Liu, Alexey Yamilov, Hui Cao
Physics Faculty Research & Creative Works
We studied the effect of Kerr nonlinearity on lasing in defect modes of weakly disordered photonic crystals. Our timeindependent calculation based on selfconsistent nonlinear transfer matrix method shows that Kerr nonlinearity modifies both frequencies and quality factors of defect modes. We also used a timedependent algorithm to investigate the dynamic nonlinear effect. Under continuous pumping, the spatial sizes and intensities of defect lasing modes are changed by Kerr nonlinearity. Such changes are sensitive to the nonlinear response time.
Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, EunJoo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto
Tev Black Hole Fragmentation And Detectability In Extensive Air Showers, EunJoo Ahn, Maximo Ave, Marco Cavaglia, Angela V. Olinto
Physics Faculty Research & Creative Works
In models with large extra dimensions, particle collisions with a centerofmass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects. Since cosmic rays have been observed with energies above 10^{8} TeV, gravitational effects in the TeV energy range can, in principle, be observed by ultrahigh energy cosmic ray detectors. We consider the interaction of ultrahigh energy neutrinos in the atmosphere and compare extensive air showers from TeV black hole formation and fragmentation with standard model processes. Departures from the standard model predictions arise in the interaction cross sections and in the multiplicity of secondary particles. Large ...
Charge Transfer In Slow Collisions Of H⁺ With Na, AnhThu Le, ChenNan Liu, C. D. Lin
Charge Transfer In Slow Collisions Of H⁺ With Na, AnhThu Le, ChenNan Liu, C. D. Lin
Physics Faculty Research & Creative Works
We reexamined chargetransfer cross sections for protons colliding with Na(3s) atoms for collision energies from the threshold at 1.7 eV to 40 eV using the recently developed hyperspherical closecoupling method. Our results disagree with the recent calculations by Dutta et al. [Phys. Rev. A 63, 022709 (2001)], but are in good agreement with the earlier calculations of Croft and Dickinson [J. Phys. B 29, 57 (1996)] except at energies below 3 eV. Our calculations support the doubt on the experimental data of Kushawaha.
Extrapolation Of The ZαExpansion And TwoLoop BoundState Energy Shifts, Ulrich D. Jentschura
Extrapolation Of The ZαExpansion And TwoLoop BoundState Energy Shifts, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
Quantum electrodynamic (QED) effects that shift the binding energies of hydrogenic energy levels have been expressed in terms of a semianalytic expansion in powers of Zα and ln[(Zα)^{2}], where Z is the nuclear charge number and α is the finestructure constant. For many QED effects, numerical data are available in the domain of high Z where the Zα expansion fails. In this Letter, we demonstrate that it is possible, within certain limits of accuracy, to extrapolate the Zαexpansion from the lowZ to the highZ domain. We also review twoloop selfenergy effects and provide an estimate for the problematic ...
ProjectileCharge Sign Dependence Of FourParticle Dynamics In Helium Double Ionization, Daniel Fischer, Robert Moshammer, Alexander Dorn, Jose R. Crespo LopezUrrutia, Bernold Feuerstein, C. Hohr, Claus Dieter Schroter, Siegbert Hagmann, Holger Kollmus, Rido Mann, Bhas Bapat, Joachim Hermann Ullrich, Holger Kollmus
ProjectileCharge Sign Dependence Of FourParticle Dynamics In Helium Double Ionization, Daniel Fischer, Robert Moshammer, Alexander Dorn, Jose R. Crespo LopezUrrutia, Bernold Feuerstein, C. Hohr, Claus Dieter Schroter, Siegbert Hagmann, Holger Kollmus, Rido Mann, Bhas Bapat, Joachim Hermann Ullrich, Holger Kollmus
Physics Faculty Research & Creative Works
Double ionization of helium by 6 MeV proton impact has been explored in a kinematically complete experiment using a “reaction microscope.” For the first time, fully differential cross sections for positively charged projectiles have been obtained and compared with data from 2 keV electron impact. The significant differences observed in the angular distribution of the ejected electrons are attributed to the charge sign of the projectile, resulting in different dynamics of the fourparticle Coulomb system, which is not considered in the first Born approximation.
Hyperspherical CloseCoupling Calculations For ChargeTransfer Cross Sections In He²⁺ +H(1s) Collisions At Low Energies, ChenNan Liu, AnhThu Le, Toru Morishita, B. D. Esry, C. D. Lin
Hyperspherical CloseCoupling Calculations For ChargeTransfer Cross Sections In He²⁺ +H(1s) Collisions At Low Energies, ChenNan Liu, AnhThu Le, Toru Morishita, B. D. Esry, C. D. Lin
Physics Faculty Research & Creative Works
A theory for ionatom collisions at low energies based on the hyperspherical closecoupling (HSCC) method is presented. In hyperspherical coordinates the wave function is expanded in analogy to the BornOppenheimer approximation where the adiabatic channel functions are calculated with Bspline basis functions while the coupled hyperradial equations are solved by a combination of Rmatrix propagation and the slow/smooth variable discretization method. The HSCC method is applied to calculate chargetransfer cross sections for He²⁺ +H(1s)>He⁺ (n=2) + H⁺ reactions at centerofmass energies from 10 eV to 4 keV. The results are shown to be in general good agreement ...
Asymptotic Properties Of SelfEnergy Coefficients, Ulrich D. Jentschura, Eric Olivier Le Bigot, Peter J. Mohr, Paul Indelicato, Gerhard Soff
Asymptotic Properties Of SelfEnergy Coefficients, Ulrich D. Jentschura, Eric Olivier Le Bigot, Peter J. Mohr, Paul Indelicato, Gerhard Soff
Physics Faculty Research & Creative Works
We investigate the asymptotic properties of higherorder binding corrections to the oneloop selfenergy of excited states in atomic hydrogen. We evaluate the historically problematic A_{60} coefficient for all P states with principal quantum numbers n ≤ 7 and D states with n ≤ 8 and find that a satisfactory representation of the n dependence of the coefficients requires a threeparameter fit. For the highenergy contribution to A_{60}, we find exact formulas. The results obtained are relevant for the interpretation of highprecision laser spectroscopic measurements.
DisorderInduced Rounding Of Certain Quantum Phase Transitions, Thomas Vojta
DisorderInduced Rounding Of Certain Quantum Phase Transitions, Thomas Vojta
Physics Faculty Research & Creative Works
We study the influence of quenched disorder on quantum phase transitions in systems with overdamped dynamics. For Ising orderparameter symmetry disorder destroys the sharp phase transition by rounding because a static order parameter can develop on rare spatial regions. This leads to an exponential dependence of the order parameter on the coupling constant. At finite temperatures the static order on the rare regions is destroyed. This restores the phase transition and leads to a double exponential relation between critical temperature and coupling strength. We discuss the behavior based on Lifshitztail arguments and illustrate the results by simulations of a model ...
Temperature Dependence Of Droplet Nucleation In A Yukawa Fluid, Jinsong Li, Gerald Wilemski
Temperature Dependence Of Droplet Nucleation In A Yukawa Fluid, Jinsong Li, Gerald Wilemski
Physics Faculty Research & Creative Works
We have studied the temperature dependence of gastoliquid nucleation in Yukawa fluids with gradient theory and density functional theory. Each of these nonclassical theories exhibits a weaker (i.e., better) temperature dependence than classical nucleation theory. At fixed temperature, the reversible work to form a critical nucleus found from gradient theory approaches the value given by density functional theory as the supersaturation increases. At high temperatures, the two theories remain quite close over a wide range of vapor densities. As the temperature is reduced, the difference between the two theories increases with decreasing vapor density. Compared to the classical theory ...
Brane Factories, EunJoo Ahn, Marco Cavaglia, Angela V. Olinto
Brane Factories, EunJoo Ahn, Marco Cavaglia, Angela V. Olinto
Physics Faculty Research & Creative Works
We propose that higherdimensional extended objects (pbranes) are created by superPlanckian scattering processes in theories with TeV scale gravity. As an example, we compute the cross section for pbrane creation in a (n + 4)dimensional spacetime with asymmetric compactification. We find that the cross section for the formation of a brane which is wounded on a compact submanifold of size of the fundamental gravitational scale is larger than the cross section for the creation of a spherically symmetric black hole. Therefore, we predict that branes are more likely to be created than black holes in superPlanckian scattering processes ...
Dynamic Nonlinear Effect On Lasing In Random Media, B. Liu, Alexey Yamilov, Y. Ling, J. Y. Xu, Hui Cao
Dynamic Nonlinear Effect On Lasing In Random Media, B. Liu, Alexey Yamilov, Y. Ling, J. Y. Xu, Hui Cao
Physics Faculty Research & Creative Works
We investigate the dynamic effect of nonlinearity on lasing in disordered medium. The thirdorder nonlinearity not only changes frequency and size of lasing mode, but also modifies laser emission intensity and laser pulse width.
Perturbative And Nonperturbative Calculations Of ElectronHydrogen Ionization, Stephenie J. Jones, Don H. Madison, Mark D. Baertschy
Perturbative And Nonperturbative Calculations Of ElectronHydrogen Ionization, Stephenie J. Jones, Don H. Madison, Mark D. Baertschy
Physics Faculty Research & Creative Works
We compare calculations of the fully differential cross section for ionization of atomic hydrogen by electron impact using two different theoriesthe perturbative CDWEIS (continuum distorted wave with eikonal initial state) approximation and the nonperturbative ECS (exterior complex scaling) method. For this comparison, we chose an impact energy of 54.4 eV, since this is near the lowest energy that our perturbative approach would be applicable and near the highest energy that can be tackled by the ECS method with our present computational resources. For the case of equalenergy outgoing electrons investigated here, the two theories predict nearly identical results except ...
How To Establish Successful Cooperative Student Learning Centers For Stem Courses, Ronald James Bieniek, Douglas R. Carroll, Cesar Mendoza, Oran Allan Pringle, Ekkehard Sinn, KaiTak Wan, Donald C. Wunsch
How To Establish Successful Cooperative Student Learning Centers For Stem Courses, Ronald James Bieniek, Douglas R. Carroll, Cesar Mendoza, Oran Allan Pringle, Ekkehard Sinn, KaiTak Wan, Donald C. Wunsch
Physics Faculty Research & Creative Works
Students learn more if they are actively involved in the learning process, particularly in a cooperative manner. Several UMR faculty have operated coursebased learning centers (LCs) as part of the campuswide Learning Enhancement Across Disciplines (LEAD) Program of student learning assistance and enhancement. LCs are designed to assist large numbers of students in a cost and timeefficient manner that promotes student engagement without requiring undue amounts of faculty time. Course instructors spend time in the open learning environment of the LC, in lieu of office hours, guiding students to master course material and skills in their evolution from novice to ...