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 Publications (1)
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Articles 1  30 of 49
FullText Articles in Physics
A ComputationallyEfficient Bound For The Variance Of Measuring The Orientation Of Single Molecules, Tingting Wu, Tianben Ding, Hesam Mazidi, Oumeng Zhang, Matthew D. Lew
A ComputationallyEfficient Bound For The Variance Of Measuring The Orientation Of Single Molecules, Tingting Wu, Tianben Ding, Hesam Mazidi, Oumeng Zhang, Matthew D. Lew
Electrical & Systems Engineering Publications and Presentations
Modulating the polarization of excitation light, resolving the polarization of emitted fluorescence, and point spread function (PSF) engineering have been widely leveraged for measuring the orientation of single molecules. Typically, the performance of these techniques is optimized and quantified using the CramérRao bound (CRB), which describes the best possible measurement variance of an unbiased estimator. However, CRB is a local measure and requires exhaustive sampling across the measurement space to fully characterize measurement precision. We develop a global variance upper bound (VUB) for fast quantification and comparison of orientation measurement techniques. Our VUB tightly bounds the diagonal elements of the ...
Measuring Localization Confidence For Quantifying Accuracy And Heterogeneity In SingleMolecule SuperResolution Microscopy, Hesam Mazidi, Tianben Ding, Arye Nehorai, Matthew D. Lew
Measuring Localization Confidence For Quantifying Accuracy And Heterogeneity In SingleMolecule SuperResolution Microscopy, Hesam Mazidi, Tianben Ding, Arye Nehorai, Matthew D. Lew
Electrical & Systems Engineering Publications and Presentations
We present a computational method, termed Wassersteininduced flux (WIF), to robustly quantify the accuracy of individual localizations within a singlemolecule localization microscopy (SMLM) dataset without ground truth knowledge of the sample. WIF relies on the observation that accurate localizations are stable with respect to an arbitrary computational perturbation. Inspired by optimal transport theory, we measure the stability of individual localizations and develop an efficient optimization algorithm to compute WIF. We demonstrate the advantage of WIF in accurately quantifying imaging artifacts in highdensity reconstruction of a tubulin network. WIF represents an advance in quantifying systematic errors with unknown and complex distributions ...
First Exclusive Measurement Of Deeply Virtual Compton Scattering Off ^{4}He: Toward The 3d Tomography Of Nuclei, M. Hattawy, N. A. Baltzell, R. Dupré, K. Hafidi, S. Stepanyan, S. Bültmann, R. De Vita, A. El Alaoui, L. El Fassi, H. Egiyan, B. Torayev, D. Adikaram, M. J. Amaryan, G. Charles, M. Khachatryan, A. Klein, S. E. Kuhn, M. Mayer, Y. Prok, L. B. Weinstein, Z. W. Zhao
First Exclusive Measurement Of Deeply Virtual Compton Scattering Off 4He: Toward The 3d Tomography Of Nuclei, M. Hattawy, N. A. Baltzell, R. Dupré, K. Hafidi, S. Stepanyan, S. Bültmann, R. De Vita, A. El Alaoui, L. El Fassi, H. Egiyan, B. Torayev, D. Adikaram, M. J. Amaryan, G. Charles, M. Khachatryan, A. Klein, S. E. Kuhn, M. Mayer, Y. Prok, L. B. Weinstein, Z. W. Zhao
Physics Faculty Publications
We report on the first measurement of the beamspin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment uses the 6 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator at Jefferson Lab incident on a pressurized ^{4}He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron is detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber is used to detect the recoiling ^{4 ...}
ManyParticle Systems, 5, David Peak
ManyParticle Systems, 5, David Peak
Many Particles
Photons as T → 0 K
Photons are massless bosons. Because they are massless, any number of them can be added or subtracted without changing the photon system energy. (For example, a 1 eV photon can be exchanged for one hundred 0.01 eV photons, without changing system energy.) As a result, the chemical potential for photons is zero.
Foundations, 2, David Peak
Foundations, 2, David Peak
Foundations
The double slit experiment in dim light – photons!
Let’s imagine doing the double slit experiment again, but now in very dim light. To do so requires putting the laser, plate, and collector in a sealed, lighttight box. Inserting neutral density filters in the beam between the laser and the double slit plate decreases the intensity of the beam striking the plate. In fact, the experiment can be done at such a low intensity that a human eye will not see any light on the CCD collector; but the CCD can. Under these conditions, the number of pixels that “light ...
Particle Production In A Gravitational Wave Background, Preston Jones, Patrick Mcdougall, Douglas Singleton
Particle Production In A Gravitational Wave Background, Preston Jones, Patrick Mcdougall, Douglas Singleton
Publications
In this article, the authors study the possibility that massless particles, such as photons, are produced by a gravitational wave. That such a process should occur is implied by treelevel Feynman diagrams such as two gravitons turning into two photons, i.e., g + g → γ + γ. Here we calculate the rate at which a gravitational wave creates a massless scalar field. This is done by placing the scalar field in the background of a plane gravitational wave and calculating the 4current of the scalar field. Even in the vacuum limit of the scalar field it has a nonzero vacuum expectation ...
Nonresonant TwoPhoton Transitions In Length And Velocity Gauges, Ulrich D. Jentschura
Nonresonant TwoPhoton Transitions In Length And Velocity Gauges, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We reexamine the invariance of twophoton transition matrix elements and corresponding twophoton Rabi frequencies under the "gauge" transformation from the length to the velocity gauge. It is shown that gauge invariance, in the most general sense, only holds at exact resonance, for both onecolor as well as twocolor absorption. The arguments leading to this conclusion are supported by analytic calculations which express the matrix elements in terms of hypergeometric functions, and ramified by a "master identity" which is fulfilled by offdiagonal matrix elements of the Schrödinger propagator under the transformation from the velocity to the length gauge. The study of ...
The Singing Cymbal: Is It Really Photon Momentum?, Thomas R. Moore, Samantha Collin, Nikki Etchenique
The Singing Cymbal: Is It Really Photon Momentum?, Thomas R. Moore, Samantha Collin, Nikki Etchenique
StudentFaculty Collaborative Research Publications
A simple demonstration that is occasionally used in the classroom to show that light carries momentum involves making an orchestral cymbal audibly ring using light from a common photoflash. A metal plate or a piece of foil can also be used, however, it appears that many people use a cymbal because the sound is easily heard at a reasonable distance. It is such an impressive example of the effects attributable to photon momentum that it is posted on the CERN website for educational under the name “singing cymbal.” Although it is an impressive demonstration, a series of simple classroom experiments ...
Gasb Thermophotovoltaic Cells Grown On Gaas By Molecular Beam Epitaxy Using Interfacial Misfit Arrays, BorChau Juang, Ramesh B. Laghumavarapu, Brandon J. Foggo, Paul J. Simmonds, Andrew Lin, Baolai Liang, Diana L. Huffaker
Gasb Thermophotovoltaic Cells Grown On Gaas By Molecular Beam Epitaxy Using Interfacial Misfit Arrays, BorChau Juang, Ramesh B. Laghumavarapu, Brandon J. Foggo, Paul J. Simmonds, Andrew Lin, Baolai Liang, Diana L. Huffaker
Physics Faculty Publications and Presentations
There exists a longterm need for foreign substrates on which to grow GaSbbased optoelectronic devices. We address this need by using interfacial misfit arrays to grow GaSbbased thermophotovoltaic cells directly on GaAs (001) substrates and demonstrate promising performance. We compare these cells to control devices grown on GaSb substrates to assess device properties and material quality. The room temperature dark current densities show similar characteristics for both cells on GaAs and on GaSb. Under solar simulation the cells on GaAs exhibit an opencircuit voltage of 0.121 V and a shortcircuit current density of 15.5 mA/cm^{2}. In ...
Cosmic Background Radiation, Sree Ram Valluri, B G. Sidharth
Cosmic Background Radiation, Sree Ram Valluri, B G. Sidharth
Physics and Astronomy Publications
It is shown that a collection of photons with nearly the same frequency exhibits a “condensation” type of phenomenon corresponding to a peak intensity. The observed cosmic background radiation can be explained from this standpoint.We have obtained analogous results by extremization of the occupation number for photons with the use of the Lambert W function. Some of the interesting applications of this function are briefly discussed in the context of graphene which exhibits an interesting two dimensional structure with several characteristic properties and diverse practical applications.
Benchmarking Accurate Spectral Phase Retrieval Of Single Attosecond Pulses, Hui Wei, AnhThu Le, Toru Morishita, Chao Yu, C. D. Lin
Benchmarking Accurate Spectral Phase Retrieval Of Single Attosecond Pulses, Hui Wei, AnhThu Le, Toru Morishita, Chao Yu, C. D. Lin
Physics Faculty Research & Creative Works
A single extremeultraviolet (XUV) attosecond pulse or pulse train in the time domain is fully characterized if its spectral amplitude and phase are both determined. The spectral amplitude can be easily obtained from photoionization of simple atoms where accurate photoionization cross sections have been measured from, e.g., synchrotron radiations. To determine the spectral phase, at present the standard method is to carry out XUV photoionization in the presence of a dressing infrared (IR) laser. In this work, we examine the accuracy of current phase retrieval methods (PROOF and iPROOF) where the dressing IR is relatively weak such that photoelectron ...
Gravitational Correction To Vacuum Polarization, Ulrich D. Jentschura
Gravitational Correction To Vacuum Polarization, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We consider the gravitational correction to (electronic) vacuum polarization in the presence of a gravitational background field. The Dirac propagators for the virtual fermions are modified to include the leading gravitational correction (potential term) which corresponds to a coordinatedependent fermion mass. The mass term is assumed to be uniform over a length scale commensurate with the virtual electronpositron pair. The onmass shell renormalization condition ensures that the gravitational correction vanishes on the mass shell of the photon, i.e., the speed of light is unaffected by the quantum field theoretical loop correction, in full agreement with the equivalence principle. Nontrivial ...
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 ...
Longitudinal TargetSpin Asymmetries For Deeply Virtual Compton Scattering, E. Seder, A. Biselli, S. Bültmann, A. Klein, S. E. Kuhn, Y. Prok, Clas Collaboration
Longitudinal TargetSpin Asymmetries For Deeply Virtual Compton Scattering, E. Seder, A. Biselli, S. Bültmann, A. Klein, S. E. Kuhn, Y. Prok, Clas Collaboration
Physics Faculty Publications
A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6 GeV electron beam, a longitudinally polarized proton target, and the CEBAF Large Acceptance Spectrometer. Targetspin asymmetries for e p → e'p'ɣ events, which arise from the interference of the deeply virtual Compton scattering and the BetheHeitler processes, were extracted over the widest kinematics in Q^{2}, x_{B}, t, and ɸ, for 166 fourdimensional bins. In the framework of generalized parton distributions, at leading twist the t dependence of these asymmetries provides insight into the spatial ...
Towards A Resolution Of The Proton Form Factor Problem: New Electron And Positron Scattering Data, Clas Collaboration, D. Adikaram, L. B. Weinstein, R. P. Bennett, K. P, Adhikari, M. J. Amaryan, S. Careccia, L. El Fassi, C. E. Hyde, A. Klein, S E. Kuhn, M. Mayer, Z. W. Zhao
Towards A Resolution Of The Proton Form Factor Problem: New Electron And Positron Scattering Data, Clas Collaboration, D. Adikaram, L. B. Weinstein, R. P. Bennett, K. P, Adhikari, M. J. Amaryan, S. Careccia, L. El Fassi, C. E. Hyde, A. Klein, S E. Kuhn, M. Mayer, Z. W. Zhao
Physics Faculty Publications
There is a significant discrepancy between the values of the proton electric form factor, G^{p}_{E}, extracted using unpolarized and polarized electron scattering. Calculations predict that small twophoton exchange (TPE) contributions can significantly affect the extraction of G^{p}_{E}from the unpolarized electronproton cross sections. We determined the TPE contribution by measuring the ratio of positronproton to electronproton elastic scattering cross sections using a simultaneous, tertiary electronpositron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon ...
Measurement Of Isolated Photon Production In Pp And Pbpb Collisions At √Snn = 2.76 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, Jose LazoFlores, Helena Malbouisson, Sudhir Malik, Gregory Snow
Measurement Of Isolated Photon Production In Pp And Pbpb Collisions At √Snn = 2.76 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, Jose LazoFlores, Helena Malbouisson, Sudhir Malik, Gregory Snow
Kenneth Bloom Publications
Isolated photon production is measured in proton–proton and lead–lead collisions at nucleon–nucleon centreofmass energies of 2.76 TeV in the pseudorapidity range η < 1.44 and transverse energies E_{T} between 20 and 80 GeV with the CMS detector at the LHC. The measured E_{T} spectra are found to be in good agreement with nexttoleadingorder perturbative QCD predictions. The ratio of PbPb to pp isolated photon E_{T} differential yields, scaled by the number of incoherent nucleon–nucleon collisions, is consistent with unity for all PbPb reaction centralities.
Modeling FreeCarrier Absorption And Avalanching By Ultrashort Laser Pulses, Jeremy R. Gulley
Modeling FreeCarrier Absorption And Avalanching By Ultrashort Laser Pulses, Jeremy R. Gulley
Faculty Publications
In the past decade it was demonstrated experimentally that negativelychirped laser pulses can lower the surface LIDT for wide bandgap materials by decreasing the number of photons required for photoionization on the leading edge of the pulse. Similarly, simulations have shown that positivelychirped pulses resulting from selffocusing and selfphase modulation in bulk dielectrics can alter the onset of laserinduced material modifications by increasing the number of photons required for photoionization on the leading edge of the pulse. However, the role of multichromatic effects in freecarrier absorption and avalanching has yet to be addressed. In this work a frequencyselective model of ...
SelfImaging Of Molecules From Diffraction Spectra By LaserInduced Rescattering Electrons, Junliang Xu, Zhangjin Chen, AnhThu Le, C. D. Lin
SelfImaging Of Molecules From Diffraction Spectra By LaserInduced Rescattering Electrons, Junliang Xu, Zhangjin Chen, AnhThu Le, C. D. Lin
Physics Faculty Research & Creative Works
We study highenergy angleresolved photoelectron spectra of molecules in strong fields. In an oscillating laser electric field, electrons released earlier in the pulse may return to recollide with the target ion, in a process similar to scattering by laboratory prepared electrons. If midinfrared lasers are used, we show that the images generated by the returning electrons are similar to images observed in typical gasphase electron diffraction (GED). These spectra can be used to retrieve the positions of atoms in a molecule as in GED. Since infrared laser pulses of durations of a few femtoseconds are already available today, the study ...
Investigating TwoPhoton Double Ionization Of D₂ By XuvPumpXuvProbe Experiments, Yuhai Jiang, Artem Rudenko, Jhon Fredy PerezTorres, 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 SanzVicario, Jeroen Van Tilborg, Ali Belkacem, Michael Schulz, Kiyoshi Ueda, Stefan Dusterer, Rolf Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich
Investigating TwoPhoton Double Ionization Of D₂ By XuvPumpXuvProbe Experiments, Yuhai Jiang, Artem Rudenko, Jhon Fredy PerezTorres, 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 SanzVicario, Jeroen Van Tilborg, Ali Belkacem, Michael Schulz, Kiyoshi Ueda, Stefan Dusterer, Rolf Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
We used a splitmirror setup attached to a reaction microscope at the freeelectron laser in Hamburg (FLASH) to perform an XUVpumpXUVprobe experiment by tracing the ultrafast nuclear wavepacket motion in the D2 ^{+}(1sσg) with <10 fs time resolution. Comparison with timedependent calculations shows excellent agreement with the measured vibrational period of 22±4 fs in D2^{+}, points to the importance of accurately knowing the internuclear distancedependent ionization probability, and paves the way to control sequential and nonsequential twophoton doubleionization contributions.
Theoretical Study Of Photoelectron Angular Distributions In SinglePhoton Ionization Of Aligned N₂ And Co₂, Cheng Jin, AnhThu Le, SongFeng Zhao, R. R. Lucchese, C. D. Lin
Theoretical Study Of Photoelectron Angular Distributions In SinglePhoton Ionization Of Aligned N₂ And Co₂, Cheng Jin, AnhThu Le, SongFeng Zhao, R. R. Lucchese, C. D. Lin
Physics Faculty Research & Creative Works
We calculate photoelectron angular distributions (PADs) resulting from singlephoton (43 eV) ionization of molecules that have been transiently aligned with a short laser pulse. The total ionization cross sections of N₂ and CO₂ vs the time delay between the aligning laser pulse and the soft xray photon are calculated and compared to experimental results reported by I. Thomann et al. [J. Phys. Chem. A 112, 9382 (2008)]. We present the PADs from these aligned molecules in the laboratory frame which can be compared directly with future experiments from aligned N₂ and CO₂. The alignment dependence of singlephoton ionization, multiphoton ionization ...
Correlated TwoPhoton Emission By Transitions Of DiracVolkov States In Intense Laser Fields: Qed Predictions, Erik Lotstedt, Ulrich D. Jentschura
Correlated TwoPhoton Emission By Transitions Of DiracVolkov States In Intense Laser Fields: Qed Predictions, Erik Lotstedt, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
In an intense laser field, an electron may decay by emitting a pair of photons. The two photons emitted during the process, which can be interpreted as a laserdressed double Compton scattering, remain entangled in a quantifiable way: namely, the socalled concurrence of the photon polarizations gives a gaugeinvariant measure of the correlation of the hard gamma rays. We calculate the differential rate and concurrence for a backscattering setup of the electron and photon beam, employing Volkov states and propagators for the electron lines, thus accounting nonperturbatively for the electronlaser interaction. The nonperturbative results are shown to differ significantly compared ...
Relativistic (Zα)2 Corrections And Leading Quantum Electrodynamic Corrections To The TwoPhoton Decay Rate Of Ionic States, Benedikt J. Wundt, Ulrich D. Jentschura
Relativistic (Zα)2 Corrections And Leading Quantum Electrodynamic Corrections To The TwoPhoton Decay Rate Of Ionic States, Benedikt J. Wundt, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We calculate the relativistic corrections of relative order (Zα) 2 to the twophoton decay rate of higher excited S and D states in ionic atomic systems, and we also evaluate the leading radiative corrections of relative order α (Zα) 2 ln [(Zα) 2]. We thus complete the theory of the twophoton decay rates up to relative order α3 ln (α). An approach inspired by nonrelativistic quantum electrodynamics is used. We find that the corrections of relative order (Zα) 2 to the twophoton decay are given by the Zitterbewegung, by the spinorbit coupling and by relativistic corrections to the electron mass ...
Quantitative Rescattering Theory For LaserInduced HighEnergy Plateau Photoelectron Spectra, Zhangjin Chen, AnhThu Le, Toru Morishita, C. D. Lin
Quantitative Rescattering Theory For LaserInduced HighEnergy Plateau Photoelectron Spectra, Zhangjin Chen, AnhThu Le, Toru Morishita, C. D. Lin
Physics Faculty Research & Creative Works
A comprehensive quantitative rescattering (QRS) theory for describing the production of highenergy photoelectrons generated by intense laser pulses is presented. According to the QRS, the momentum distributions of these electrons can be expressed as the product of a returning electron wave packet with the elastic differential cross sections (DCS) between free electrons with the target ion. We show that the returning electron wave packets are determined mostly by the lasers only and can be obtained from the strong field approximation. The validity of the QRS model is carefully examined by checking against accurate results from the solution of the timedependent ...
Accurate Retrieval Of Target Structures And Laser Parameters Of FewCycle Pulses From Photoelectron Momentum Spectra, Samuel Micheau, Zhangjin Chen, AnhThu Le, J. Rauschenberger, M. F. Kling, C. D. Lin
Accurate Retrieval Of Target Structures And Laser Parameters Of FewCycle Pulses From Photoelectron Momentum Spectra, Samuel Micheau, Zhangjin Chen, AnhThu Le, J. Rauschenberger, M. F. Kling, C. D. Lin
Physics Faculty Research & Creative Works
We illustrate a new method of analyzing threedimensional momentum images of highenergy photoelectrons generated by intense phasestabilized fewcycle laser pulses. Using photoelectron momentum spectra that were obtained by velocitymap imaging of abovethreshold ionization of xenon and argon targets, we show that the absolute carrierenvelope phase, the laser peak intensity, and pulse duration can be accurately determined simultaneously (with an error of a few percent). We also show that the target structure, in the form of electrontarget ion elastic differential cross sections, can be retrieved over a range of energies. The latter offers the promise of using lasergenerated electron spectra for ...
CoulombFieldInduced Conversion Of A HighEnergy Photon Into A Pair Assisted By A Counterpropagating Laser Beam, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
CoulombFieldInduced Conversion Of A HighEnergy Photon Into A Pair Assisted By A Counterpropagating Laser Beam, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
The laserinduced modification of a fundamental process of quantum electrodynamics, the conversion of a highenergy gamma photon in the Coulomb field of a nucleus into an electronpositron pair, is studied theoretically. Although the employed formalism allows for the general case where the gamma photon and laser photons cross at an arbitrary angle, we here focus on a theoretically interesting and numerically challenging setup, where the laser beam and gamma photon counterpropagate and impinge on a nucleus at rest. For a peak laser field smaller than the critical Schwinger field and gamma photon energy larger than the fieldfree threshold, the total ...
Laser Channeling Of BetheHeitler Pairs, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Laser Channeling Of BetheHeitler Pairs, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
Electronpositron pair creation is analyzed for an arrangement involving three external fields: a highfrequency gamma photon, the Coulomb field of a nucleus, and a strong laser wave. The frequency of the incoming gamma photon is assumed to be larger than the threshold for pair production in the absence of a laser, and the peak electric field of the laser is assumed to be much weaker than Schwinger's critical field. The total number of pairs produced is found to be essentially unchanged by the laser field, while the differential cross section is drastically modified. We show that the laser can ...
Potential For Ultrafast Dynamic Chemical Imaging With FewCycle Infrared Lasers, Toru Morishita, AnhThu Le, Zhangjin Chen, C. D. Lin
Potential For Ultrafast Dynamic Chemical Imaging With FewCycle Infrared Lasers, Toru Morishita, AnhThu Le, Zhangjin Chen, C. D. Lin
Physics Faculty Research & Creative Works
We studied the photoelectron spectra generated by an intense few cycle infrared laser pulse. By focusing on the angular distributions of the back rescattered high energy photoelectrons, we show that accurate differential elastic scattering crosssections of the target ion by free electrons can be extracted. Since the incident direction and the energy of the free electrons can be easily changed by manipulating the laser's polarization, intensity and wavelength, these extracted elastic scattering crosssections, in combination with more advanced inversion algorithms, may be used to reconstruct the effective singlescattering potential of the molecule, thus opening up the possibility of using ...
Bremsstrahlung In Α Decay Reexamined, H. Boie, Heiko Scheit, Ulrich D. Jentschura, F. Kock, M. Lauer, A. I. Milstein, Ivan S. Terekhov, Dirk Schwalm
Bremsstrahlung In Α Decay Reexamined, H. Boie, Heiko Scheit, Ulrich D. Jentschura, F. Kock, M. Lauer, A. I. Milstein, Ivan S. Terekhov, Dirk Schwalm
Physics Faculty Research & Creative Works
A highstatistics measurement of bremsstrahlung emitted in the α decay of ^{210}Po has been performed, which allows us to follow the photon spectra up to energies of ~500keV. The measured differential emission probability is in good agreement with our theoretical results obtained within the quasiclassical approximation as well as with the exact quantum mechanical calculation. It is shown that, due to the small effective electric dipole charge of the radiating system, a significant interference between the electric dipole and quadrupole contributions occurs, which is altering substantially the angular correlation between the α particle and the emitted photon.
Photon Angular Distribution And NuclearState Alignment In Nuclear Excitation By Electron Capture, Adriana Palffy, Zoltan Harman, Andrey S. Surzhykov, Ulrich D. Jentschura
Photon Angular Distribution And NuclearState Alignment In Nuclear Excitation By Electron Capture, Adriana Palffy, Zoltan Harman, Andrey S. Surzhykov, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
The alignment of nuclear states resonantly formed in nuclear excitation by electron capture (NEEC) is studied by means of a density matrix technique. The vibrational excitations of the nucleus are described by a collective model and the electrons are treated in a relativistic framework. Formulas for the angular distribution of photons emitted in the nuclear relaxation are derived. We present numerical results for alignment parameters and photon angular distributions for a number of heavy elements in the case of E2 nuclear transitions. Our results are intended to help future experimental attempts to discern NEEC from radiative recombination, which is the ...
Vacuum SelfFocusing Of Very Intense Laser Beams, Dmitri Kharzeev, Kirill Tuchin
Vacuum SelfFocusing Of Very Intense Laser Beams, Dmitri Kharzeev, Kirill Tuchin
Physics and Astronomy Publications
We argue that longrange photonphoton attraction induced by the dipole interaction of two electronpositron loops can lead to "vacuum selffocusing" of very intense laser beams. The focusing angle Î¸F is found to increase with the beam intensity I as Î¸F âˆ¼ I4/3; for the laser beams available at present or in the near future, Î¸F 1010  107.