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- Peter Dowben Publications (8)
- David Sellmyer Publications (7)
- Roger Kirby Publications (6)
- Department of Physics and Astronomy: Faculty Publications (5)
- Ralph Skomski Publications (5)
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- Robert Katz Publications (5)
- Christian Binek Publications (4)
- Timothy J. Gay Publications (4)
- Donald Umstadter Publications (3)
- Sy-Hwang Liou Publications (2)
- Anthony F. Starace Publications (1)
- Edward Schmidt Publications (1)
- John R. Hardy Papers (1)
- M. Eugene Rudd Publications (1)
- Paul Burrow Publications (1)
- Robert G. Fuller Publications (1)
- Stephen Ducharme Publications (1)
Articles 31 - 56 of 56
Full-Text Articles in Physical Sciences and Mathematics
Blocking Of Logarithmic Temporal Relaxation Of Magnetic Remanence By Piezomagnetically Induced Domains In Fe1-XZnXF2, J. Kushauer, Christian Binek, Wolfgang Kleemann
Blocking Of Logarithmic Temporal Relaxation Of Magnetic Remanence By Piezomagnetically Induced Domains In Fe1-XZnXF2, J. Kushauer, Christian Binek, Wolfgang Kleemann
Christian Binek Publications
Faraday rotation and superconducting quantum interference device magnetometry were used to investigate the relaxation of the weak-field induced remanence, µ, of the random-field Ising model system Fe1-xZnxF2. The stretched logarithmic decay law, as predicted by Nattermann and Vilfan for the case of compact domains with fractal surfaces, was confirmed for freezing fields of 3≤B≤5 T. Virtually constant remanence, µ, was found at low fields, 0.0002≤B≤1.5 T. This ferrimagnetic moment is due to the piezomagnetic effect acting on random-stress induced immobile domains. Chemical etching, which removes surface stress originating from the sample preparation, proves to …
Low-Temperature Characterization Of The Magnetic Properties Of Mnbial Thin Films, Kurt W. Wierman, J. X. Shen, Roger D. Kirby, David J. Sellmyer
Low-Temperature Characterization Of The Magnetic Properties Of Mnbial Thin Films, Kurt W. Wierman, J. X. Shen, Roger D. Kirby, David J. Sellmyer
Roger Kirby Publications
The magnetic properties of thin-film samples of MnBi0.8Alx with aluminum concentrations of x = 0.0, 0.4, 0.6, and 0.8 were systematically studied over a temperature range of 20 to 300 K. The as-deposited films are amorphous and nonmagnetic, but highly textured polycrystalline films that are ferromagnetic are formed by annealing at 350 °C. Our measurements show that the coercivity of such films rapidly decreases, then approaches a constant value (4 kOe for x = 0.4) with increasing annealing time. Magnetic measurements show that both anisotropy and coercivity decrease with decreasing temperature. Unlike bulk MnBi, our MnBi0.8 …
Magnetization Reversal In Compositionally Modulated Tb/Fe Multilayers (Abstract), Roger D. Kirby, J. X. Shen, David J. Sellmyer
Magnetization Reversal In Compositionally Modulated Tb/Fe Multilayers (Abstract), Roger D. Kirby, J. X. Shen, David J. Sellmyer
Roger Kirby Publications
We have prepared compositionally modulated Tb(X Å) thin film multilayers with X ranging from 3.5 to 7 Å by magnetron sputtering on glass substrates. Magnetization measurements using SQUID and alternating gradient force magnetometers show that these samples have uniaxial anisotropies (Ku) up to 107 erg/cm3 and saturation magnetizations (Ms) between 50 and 350 emu/cm3. Constant field magnetization reversal measurements at room temperature show that these samples reverse by slow nucleation followed by relatively rapid domain wall motion. The samples with larger uniaxial anisotropies and smaller saturation magnetizations reverse completely …
Be Stars In Young Clusters, Shaukat N. Goderya, Edward G. Schmidt
Be Stars In Young Clusters, Shaukat N. Goderya, Edward G. Schmidt
Edward Schmidt Publications
Photometric Hχ and Hβ line indices for 71 B stars in seven galactic clusters are presented. Some stars in three of the clusters were observed at two epochs. Using these data nine Be stars were identified. Three of them were previously detected as emission-line stars, while six do not appear to have been previously recognized as such. Of the 62 stars for which we find no indication of emission, three were previously found to exhibit emission. We find that emission-line objects are absent among the most luminous early B giants.
Femtosecond Free-Electron Laser By Chirped Pulse Amplification, L.H. Yu, E. Johnson, D. Li, Donald P. Umstadter
Femtosecond Free-Electron Laser By Chirped Pulse Amplification, L.H. Yu, E. Johnson, D. Li, Donald P. Umstadter
Donald Umstadter Publications
In this work we combine elements of chirped pulse amplification techniques, now familiar in solid-state lasers, with an amplifier based upon a seeded free-electron laser (FEL). The resulting device would produce amplified pulses of unprecedented brevity at wavelengths shorter than can be currently obtained by any tunable laser system. We use a subharmonically seeded FEL to illustrate the concept. Radiation from a Ti:sapphire laser is frequency tripled and stretched optically to provide a coherent seed pulse for the FEL. When coupled to an electron beam inside a magnetic wiggler, the seed radiation introduces an additional energy modulation on the electron …
Electronic Structure And Magneto-Optical Properties Of Mnbi And Mnbial, Sitaram Jaswal, J. X. Shen, Roger D. Kirby, David J. Sellmyer
Electronic Structure And Magneto-Optical Properties Of Mnbi And Mnbial, Sitaram Jaswal, J. X. Shen, Roger D. Kirby, David J. Sellmyer
Roger Kirby Publications
MnBiAl films are of considerable current interest for possible magneto-optical applications because of their perpendicular anisotropy, large polar Kerr rotation, reduced grain size, and structural stability. We report here experimental and theoretical studies of the effect of Al alloying on the electronic structure and magneto-optical properties of MnBi. Our measured spectral dependencies of the polar Kerr rotation in the two systems are similar. We carried out relativistic self-consistent spin-polarized electronic structure calculations on MnBi and MnBiAl, and the calculated densities of states are in good agreement with available x-ray photoemission spectroscopy data for both materials. The spin magnetic moment of …
Magnetization Reversal In Nanoscale Magnetic Films With Perpendicular Anistropy, Roger D. Kirby, J.X. Shen, Robert J. Hardy, David J. Sellmyer
Magnetization Reversal In Nanoscale Magnetic Films With Perpendicular Anistropy, Roger D. Kirby, J.X. Shen, Robert J. Hardy, David J. Sellmyer
Department of Physics and Astronomy: Faculty Publications
We present experimental results on magnetization reversal for a class of nanoscale magnetic films with perpendicular magnetic anistropy and develop a model that describes a variety of related experiments. In this model the sample is divided into identical single domain cells that interact through dipolar fields and a nearest-neighbor domain-wall interaction. Monte Carlo simulations give insights into the relationship between macroscopic magnetic parameters and the reversal behavior and demonstrate the important role that thermal activation plays in the reversal process.
Heterojunction Fabrication By Selective Area Chemical Vapor Deposition Induced By Synchrotron Radiation, Dongjin Byun, Seong-Don Hwang, Peter A. Dowben, F. Keith Perkins, F. Filips, N.J. Ianno
Heterojunction Fabrication By Selective Area Chemical Vapor Deposition Induced By Synchrotron Radiation, Dongjin Byun, Seong-Don Hwang, Peter A. Dowben, F. Keith Perkins, F. Filips, N.J. Ianno
Peter Dowben Publications
We have fabricated a B5C, boron-carbide/Si(111) heterojunction diode by the synchrotron radiation-induced decomposition of orthocarborane. This diode can be compared with similar boron-carbide/Si(111) heterojunction diodes fabricated by plasma enhanced chemical vapor deposition. The synchrotron radiation induced chemical vapor deposition is postulated to occur via the decomposition of weakly chemisorbed species and the results suggest that “real-time'' projection lithography (selective area deposition) of boron-carbide devices is possible.
Parallels Between High Doubly Excited State Spectra In H– And Li– Photodetachment, Cheng Pan, Anthony F. Starace, Chris H. Greene
Parallels Between High Doubly Excited State Spectra In H– And Li– Photodetachment, Cheng Pan, Anthony F. Starace, Chris H. Greene
Anthony F. Starace Publications
Eigenchannel R-matrix calculations for photodetachment of H– up to the H(n = 6) threshold provide complete theoretical confirmation of observed high-lying, doubly excited state spectra. Long-range multipole interactions beyond the reaction volume are found to play an important role. Similar calculations for Li– photodetachment up to the Li(n = 6) threshold predict analogous resonance structures. These results indicate that recent advances in understanding two-electron correlations in H– and He have application to many electron systems.
Teaching And Learning Physics With Interactive Video, Dean Zollman, Robert Fuller
Teaching And Learning Physics With Interactive Video, Dean Zollman, Robert Fuller
Robert G. Fuller Publications
Using computer-controlled digital video, students can view and analyze the physics of events as common as the snapping of a towel, as graceful as the motion of a dancer or as extraordinary as the collapse of the Tacoma Narrows Bridge.
Slowing Of 85Rb Atoms With Isotropic Light, Herman Batelaan, S. Padua, D. H. Yang, C. Xie, R. Gupta, Harold Metcalf
Slowing Of 85Rb Atoms With Isotropic Light, Herman Batelaan, S. Padua, D. H. Yang, C. Xie, R. Gupta, Harold Metcalf
Department of Physics and Astronomy: Faculty Publications
We have demonstrated the slowing of a rubidium atomic beam by isotropic monochromatic light. The results agree with a model calculation, thus allowing its use for designing a practical isotropic light slower. The large hyperfine splittings of rubidium lead to natural multifrequency slowing, which is also included in our model.
Unoccupied Surface Electronic Structure Of Gd(0001), Dongqi Li, Peter A. Dowben, J.E. Ortega, F.J. Himpsel
Unoccupied Surface Electronic Structure Of Gd(0001), Dongqi Li, Peter A. Dowben, J.E. Ortega, F.J. Himpsel
Peter Dowben Publications
The unoccupied surface electronic structure of Gd(0001) was investigated with high-resolution inverse-photoemission spectroscopy. An empty surface state near EF is observed at Γ¯. Two other surface-sensitive features are also revealed at 1.2 and 3.1 eV above the Fermi level. Hydrogen adsorption on Gd surfaces was used to distinguish the surface-sensitive features from the bulk features. The unoccupied bulk-band critical points are determined to be Γ3- at 1.9 eV and A1 at 0.8 eV.
Magnetoresistance In Nanostructured Co-Ag Prepared By Mechanical- Alloying, J.M.D. Coey, A.J. Fagan, Ralph Skomski, J. Gregg, K. Ounadjela, S.M. Thompson
Magnetoresistance In Nanostructured Co-Ag Prepared By Mechanical- Alloying, J.M.D. Coey, A.J. Fagan, Ralph Skomski, J. Gregg, K. Ounadjela, S.M. Thompson
Ralph Skomski Publications
Fine cobalt and silver powders have been ball-milled to yield a granular solid of composition Co30Ag70 in the form of coarse powder. The material is an intimate mixture of grains of fcc CO in a silver matrix. The cobalt is in the single-domain size range, and the samples exhibit coercivity (0.07 T at 296 K) and unusual thermomagnetic effects, including field-induced unidirectional anisotropy. There is a large, isotropic negative magnetoresistance, which exceeds 10 % at 4.2 K.
Magnetoresistance In Nanostructured Co-Ag Prepared By Mechanical- Alloying, J.M.D. Coey, A.J. Fagan, Ralph Skomski, J. Gregg, K. Ounadjela, S.M. Thompson
Magnetoresistance In Nanostructured Co-Ag Prepared By Mechanical- Alloying, J.M.D. Coey, A.J. Fagan, Ralph Skomski, J. Gregg, K. Ounadjela, S.M. Thompson
Ralph Skomski Publications
Fine cobalt and silver powders have been ball-milled to yield a granular solid of composition Co30Ag70 in the form of coarse powder. The material is an intimate mixture of grains of fcc CO in a silver matrix. The cobalt is in the single-domain size range, and the samples exhibit coercivity (0.07 T at 296 K) and unusual thermomagnetic effects, including field-induced unidirectional anisotropy. There is a large, isotropic negative magnetoresistance, which exceeds 10 95 at 4.2 K.
Exchange Coupling And Energy Product In Random Two- Phase Aligned Magnets, Ralph Skomski, J.M.D. Coey
Exchange Coupling And Energy Product In Random Two- Phase Aligned Magnets, Ralph Skomski, J.M.D. Coey
Ralph Skomski Publications
Size effects in two-phase Boolean magnets composed of an aligned hard phase and a soft phase with high magnetization are investigated. In 'over-critical' magnets, where the size of the soft regions is larger than the Blochwall width δh of the hard phase, the energy product is reduced compared to the corresponding 'undercritical' magnets with small soft regions, where theoretical energy products as high as 1 M J / m3 have been predicted. Nevertheless, the theoretical energy product only gradually drops with increasing size of the soft regions, and it may still exceed the theoretical energy product 516 kJ/m …
Non-Equilibrium Gas-Phase Nitrogenation, S. Brennan, Ralph Skomski, J.M.D. Coey
Non-Equilibrium Gas-Phase Nitrogenation, S. Brennan, Ralph Skomski, J.M.D. Coey
Ralph Skomski Publications
Non-equilibrium nitrogenation of transition-metal rich rare-earth intermetallics can be used to increase the nitrogen content beyond its equilibrium concentration. For example, nitrogenation of Sm2Fe17 using ammonia yields volume expansions up to 8.3 vol %, which correspond to a composition Sm2Fe17Nx with x = 4. This effect is related to catalytic action at the metal surface where ammonia is decomposed into nitrogen and hydrogen, with nitrogen absorption on a site where it is weakly bound, as an intermediate step. For overloaded Sm2Fe17Nx with x>3 the net reaction …
Nonlinear Plasma Waves Resonantly Driven By Optimized Laser Pulse Trains, Donald Umstadter, Eric Esarey, J. Kim
Nonlinear Plasma Waves Resonantly Driven By Optimized Laser Pulse Trains, Donald Umstadter, Eric Esarey, J. Kim
Donald Umstadter Publications
A method for generating large-amplitude plasma waves, which utilizes an optimized train of independently adjustable, intense laser pulses, is discussed and analyzed. Both the pulse widths and interpulse spacings are optimally determined such that resonance is maintained and the plasma wave amplitude is maximized. By mitigating the effects of both phase and resonant detuning, and by reducing laser-plasma instabilities, the use of appropriately tailored multiple laser pulses is a highly advantageous technique for accelerating electrons. Practical methods of producing the required pulse trains are suggested.
Domainlike Antiferromagnetic Correlations Of Paramagnetic Fecl2: A Field-Induced Griffiths Phase?, Christian Binek, Wolfgang Kleemann
Domainlike Antiferromagnetic Correlations Of Paramagnetic Fecl2: A Field-Induced Griffiths Phase?, Christian Binek, Wolfgang Kleemann
Christian Binek Publications
Domainlike antiferromagnetic correlations are detected by SQUID measurements of the low-frequency susceptibility in the metamagnet FeCl2 when exposed to an axial magnetic field H at temperatures Tc (H)≤T≤TN. A distinct change of curvature of χ’’ vs T appearing at TN is explained in terms of fluctuating distributions of demagnetizing fields and, hence, transition temperatures. The field-induced dynamic domain phase—an analog of the Griffiths phase predicted for a ferromagnet with dilution x within Tc(x)≤T≤Tc(0)—is confirmed by elastic light scattering experiments.
Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek
Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek
Christian Binek Publications
Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.
Ultrashort Ultraviolet Free-Electron Lasers, Donald Umstadter, L. H. Yu, E. Johnson, D. Li
Ultrashort Ultraviolet Free-Electron Lasers, Donald Umstadter, L. H. Yu, E. Johnson, D. Li
Donald Umstadter Publications
In this work we combine elements of chirped pulse amplification (CPA) techniques, now familiar in solid-state lasers, with an amplifier based upon a seeded free-electron laser (FEL), The resulting device would produce amplified pulses of unprecedented brevity at wavelengths shorter than can be currently obtained by any tunable laser system. We use a subharmonically seeded FEL to illustrate the concept. Radiation from a Ti:sapphire laser is frequency-tripled and stretched optically to provide a coherent seed pulse for the FEL. When coupled to an electron beam inside a magnetic wiggler, the seed radiation introduces an additional energy modulation on the electron …
Dose, Robert Katz
Dose, Robert Katz
Robert Katz Publications
The universal use of dose as a normalizing parameter in radiobiology is based entirely on the availability of measuring instruments. It is a poor basis for predicting or understanding the relationship between an irradiation and the resulting end point. Energy deposited is not the cause of an interaction. It is a secondary effect. The interaction is best described by fluence and cross section. Energy deposited depends principally upon inelastic collision cross sections for the interaction of electrons with molecules. Especially for heavy-ion bombardments, for high-LET radiations, inelastic electron collision cross sections relate only remotely to the observed end points of …
Radiosensitivity Parameters For Lethal Mutagenesis In Caenorhabditis Elegans, F. A. Cucinotta, J. W. Wilson, Robert Katz
Radiosensitivity Parameters For Lethal Mutagenesis In Caenorhabditis Elegans, F. A. Cucinotta, J. W. Wilson, Robert Katz
Robert Katz Publications
For the first time track structure theory has been applied to radiobiological effects in a living organism. Data for lethal mutagenesis in Caenorhabditis elegans, obtained after irradiation with nine different types of ions of atomic number 1-57 and gamma rays have yielded radiosensitivity parameters (E0, σ0, K, m = 68 Gy, 2.5 x 10-9 cm2, 750, 2) comparable with those found for the transformation of C3HT10 1/2 cells (180 Gy, 1.15 x 10-10 cm2, 750, 2) but remote from those (E0 and σ0 = ≈2 Gy, ≈5 …
Molecular-Dynamics Simulations Of Some Baxf4 Compounds, John Flocken, Z. Mo, Wai-Ning Mei, John R. Hardy, Dorian Hatch
Molecular-Dynamics Simulations Of Some Baxf4 Compounds, John Flocken, Z. Mo, Wai-Ning Mei, John R. Hardy, Dorian Hatch
John R. Hardy Papers
We have carried out molecular-dynamics simulations on BaXF4 compounds, where X is Mg, Mn, or Zn. Ab initio potentials, with no adjustable parameters, were used to obtain short-range interactions between ion pairs. We found a polar ground-state structure which is in agreement with the A21am space group reported experimentally. We were able to reverse polarization in BaMgF4 at high temperatures, using large fields, but were unable to reverse polarization in the other compounds. The second-order phase transition in the Mn compound at 250 K was reproduced. We believe this to be the first extension of …
Survey Of Cellular Radiosensitivity Parameters, Robert Katz, Rashidah Zachariah, Francis A. Cucinotta, Chunxiang Zhang
Survey Of Cellular Radiosensitivity Parameters, Robert Katz, Rashidah Zachariah, Francis A. Cucinotta, Chunxiang Zhang
Robert Katz Publications
A model of the formation of particle tracks in emulsion has been extended through the use of biological target theory to formulate a theory of the response of biological cells and molecules of biological importance to irradiation with energetic heavy ions. For this purpose the response to γ rays is represented by the single-hit, multi-target model with parameters m and D0, while additional parameters κ (or a0) and σ0 are required to represent the size of internal cellular targets and the effective cross-sectional area of the cell nucleus, respectively, for heavy-ion bombardments. For one-or-more-hit detectors, …
Steps Toward Determinaton Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. V. Variability Of The Ultraviolet Continuum And Emission Lines Of Ngc 3783, G. A. Reichert, P. M. Rodriguez-Pascual, D. Alloin, J. Clavel, D. Michael Crenshaw, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Bradley M. Peterson, W. Wamsteker, A. Altamore, B. Altieri, K. S.J. Anderson, J. H. Blackwell Jr,, C. Boisson, N. Brosch, T. E. Carone, M. Dietrich, M. N. England, I. N. Evans, A. V. Filippenko, C. Martin Gaskell, M. Goad, P. M. Gondhalekar., K. Horne, D. Kazanas, W. Kol Latschny, A. P. Koratkar, Kirk T. Koristag, G. M. Macalpine, D. Maoz, T. Mazeh, B. Mccollum, H. Richard Miller, C. Mendes De Oliveira, Paul T. O'Brien, M. G. Pastoriza, D. Pelat, E. Perez, G. C. Perola, Richard William Pogge, R. L. Ptak, M. C. Recondo-Gonzalez, J. Rodriguez-Espinosa, E. I. Rosenblatt, A. C. Sadun, M . Santos-Lleo, J. C. Shields, C. R. Shrader, J. M. Shull, S. M. Simkin, M. L. Sitko, M. A.J Snuders, L. S. Sparke, G. M. Stirpe, R. Stoner, T. . Storchi-Bergm, W. H. Sun, T. F. Wang, W. F. Welsh, R. J. White, C. Winge, W. Zhen
Steps Toward Determinaton Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. V. Variability Of The Ultraviolet Continuum And Emission Lines Of Ngc 3783, G. A. Reichert, P. M. Rodriguez-Pascual, D. Alloin, J. Clavel, D. Michael Crenshaw, Gerard A. Kriss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Bradley M. Peterson, W. Wamsteker, A. Altamore, B. Altieri, K. S.J. Anderson, J. H. Blackwell Jr,, C. Boisson, N. Brosch, T. E. Carone, M. Dietrich, M. N. England, I. N. Evans, A. V. Filippenko, C. Martin Gaskell, M. Goad, P. M. Gondhalekar., K. Horne, D. Kazanas, W. Kol Latschny, A. P. Koratkar, Kirk T. Koristag, G. M. Macalpine, D. Maoz, T. Mazeh, B. Mccollum, H. Richard Miller, C. Mendes De Oliveira, Paul T. O'Brien, M. G. Pastoriza, D. Pelat, E. Perez, G. C. Perola, Richard William Pogge, R. L. Ptak, M. C. Recondo-Gonzalez, J. Rodriguez-Espinosa, E. I. Rosenblatt, A. C. Sadun, M . Santos-Lleo, J. C. Shields, C. R. Shrader, J. M. Shull, S. M. Simkin, M. L. Sitko, M. A.J Snuders, L. S. Sparke, G. M. Stirpe, R. Stoner, T. . Storchi-Bergm, W. H. Sun, T. F. Wang, W. F. Welsh, R. J. White, C. Winge, W. Zhen
Department of Physics and Astronomy: Faculty Publications
We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or "dips," the first lasting ≤20 days and the second ≤ 4 days, with additional episodes of relatively rapid …
Simplest Atomic System For Sub-Doppler Laser Cooling, R. Gupta, S. Padua, C. Xie, Herman Batelaan, Harold Metcalf
Simplest Atomic System For Sub-Doppler Laser Cooling, R. Gupta, S. Padua, C. Xie, Herman Batelaan, Harold Metcalf
Department of Physics and Astronomy: Faculty Publications
Sub-Doppler laser cooling requires optical pumping among differently light-shifted ground-state sublevels. We describe a study of the simplest possible angular-momentum configuration that permits all sub-Doppler cooling phenomena. The Jg = 1 ⟹ Je = 0 angular-momentum configuration shows recoil-limited cooling in the two most well-known types of polarization gradient, magnetically induced laser cooling, velocity-selective resonances, transient cooling, and velocity-selective population trapping.