Academic literature on the topic 'Physics, Low-Temperature, Quantum Simulations, Atomic Physics'
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Journal articles on the topic "Physics, Low-Temperature, Quantum Simulations, Atomic Physics"
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Hinde, Robert J. "QSATS: MPI-driven quantum simulations of atomic solids at zero temperature." Computer Physics Communications 182, no. 11 (November 2011): 2339–49. http://dx.doi.org/10.1016/j.cpc.2011.04.024.
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Obhi, R. J. K., S. W. Schaefer, C. E. Valdivia, J. R. Liu, Z. G. Lu, P. J. Poole, and K. Hinzer. "Indium arsenide single quantum dash morphology and composition for wavelength tuning in quantum dash lasers." Applied Physics Letters 122, no. 5 (January 30, 2023): 051104. http://dx.doi.org/10.1063/5.0133657.
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InAs quantum dot and dash gain media demonstrate performance benefits, such as lower threshold current densities and reduced temperature sensitivity over quantum wells for lasers operating in the C-band telecommunications window. Quantum dashes are of much interest for their higher gain over quantum dots due to an increased density of states. We combine experimental results and simulations to understand how quantum dash morphology and composition can be used to tune the emission wavelengths of these nanoparticles. Atomic force microscopy (AFM) analysis is performed to determine the effect of growth temperature and sublayer type on InAs/InGaAsP/InP nanoparticle morphology and homogeneity. Uncapped InAs nanoparticles grown by CBE on a GaAs sublayer will have dash-like geometries with heights up to 2.36 nm for growth temperatures of 500–540 °C. GaP sublayers will induce taller quantum dots except for a growth temperature of 530 °C, where quantum dashes form. The dimensions extracted from AFM scans are used in conjunction with photoluminescence data to guide parabolic band simulations of an InAs quantum dash with a GaP or GaAs sublayer and InP cap buried within InGaAsP. The calculated emission energy of a buried 30 × 300 nm quantum dash decreases by ∼100 meV for increasing heights from 1.5 to 2.5 nm, or increases by ∼100 meV by addition of 20% phosphorus in the dash and wetting layers. Modifying the quantum dash height and leveraging the As/P intermixing that occurs between the InAs and InP layers are, thus, most effective for wavelength tuning.
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Halimeh, Jad C., Maarten Van Damme, Torsten V. Zache, Debasish Banerjee, and Philipp Hauke. "Achieving the quantum field theory limit in far-from-equilibrium quantum link models." Quantum 6 (December 19, 2022): 878. http://dx.doi.org/10.22331/q-2022-12-19-878.
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Realizations of gauge theories in setups of quantum synthetic matter open up the possibility of probing salient exotic phenomena in condensed matter and high-energy physics, along with potential applications in quantum information and science technologies. In light of the impressive ongoing efforts to achieve such realizations, a fundamental question regarding quantum link model regularizations of lattice gauge theories is how faithfully they capture the quantum field theory limit of gauge theories. Recent work \cite{zache2021achieving} has shown through analytic derivations, exact diagonalization, and infinite matrix product state calculations that the low-energy physics of 1+1D U(1) quantum link models approaches the quantum field theory limit already at small link spin length S. Here, we show that the approach to this limit also lends itself to the far-from-equilibrium quench dynamics of lattice gauge theories, as demonstrated by our numerical simulations of the Loschmidt return rate and the chiral condensate in infinite matrix product states, which work directly in the thermodynamic limit. Similar to our findings in equilibrium that show a distinct behavior between half-integer and integer link spin lengths, we find that criticality emerging in the Loschmidt return rate is fundamentally different between half-integer and integer spin quantum link models in the regime of strong electric-field coupling. Our results further affirm that state-of-the-art finite-size ultracold-atom and NISQ-device implementations of quantum link lattice gauge theories have the real potential to simulate their quantum field theory limit even in the far-from-equilibrium regime.
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Huang, Yang, and Michael Widom. "Vibrational Entropy of Crystalline Solids from Covariance of Atomic Displacements." Entropy 24, no. 5 (April 28, 2022): 618. http://dx.doi.org/10.3390/e24050618.
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The vibrational entropy of a solid at finite temperature is investigated from the perspective of information theory. Ab initio molecular dynamics (AIMD) simulations generate ensembles of atomic configurations at finite temperature from which we obtain the N-body distribution of atomic displacements, ρN. We calculate the information-theoretic entropy from the expectation value of lnρN. At a first level of approximation, treating individual atomic displacements independently, our method may be applied using Debye–Waller B-factors, allowing diffraction experiments to obtain an upper bound on the thermodynamic entropy. At the next level of approximation we correct the overestimation through inclusion of displacement covariances. We apply this approach to elemental body-centered cubic sodium and face-centered cubic aluminum, showing good agreement with experimental values above the Debye temperatures of the metals. Below the Debye temperatures, we extract an effective vibrational density of states from eigenvalues of the covariance matrix, and then evaluate the entropy quantum mechanically, again yielding good agreement with experiment down to low temperatures. Our method readily generalizes to complex solids, as we demonstrate for a high entropy alloy. Further, our method applies in cases where the quasiharmonic approximation fails, as we demonstrate by calculating the HCP/BCC transition in Ti.
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Han, Chuanbing, Huihui Sun, Fudong Liu, Xiangju Zhao, and Zheng Shan. "Computational Simulations of Fabrication of Aluminum-Based Josephson Junctions: Topological Aspects of the Barrier Structure." Entropy 25, no. 2 (January 17, 2023): 182. http://dx.doi.org/10.3390/e25020182.
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Although the performance of qubits has been improved in recent years, the differences in the microscopic atomic structure of the Josephson junctions, the core devices prepared under different preparation conditions, are still underexplored. In this paper, the effects of the oxygen temperature and upper aluminum deposition rate on the topology of the barrier layer in the aluminum-based Josephson junctions have been presented by classical molecular dynamics simulations. We apply a Voronoi tessellation method to characterize the topology of the interface and central regions of the barrier layers. We find that when the oxygen temperature is 573 K and the upper aluminum deposition rate is 4 Å/ps, the barrier has the fewest atomic voids and the most closely arranged atoms. However, if only the atomic arrangement of the central region is considered, the optimal rate of the aluminum deposition is 8 Å/ps. This work provides microscopic guidance for the experimental preparation of Josephson junctions, which helps to improve the performance of qubits and accelerate the practical application of quantum computers.
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Prevenslik, Thomas. "Validity of Molecular Dynamics Heat Transfer by Quantum Mechanics." Advanced Materials Research 829 (November 2013): 803–7. http://dx.doi.org/10.4028/www.scientific.net/amr.829.803.
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MD is commonly used in computational physics to determine the atomic response of nanostructures. MD stands for molecular dynamics. With theoretical basis in statistical mechanics, MD relates the thermal energy of the atom to its momentum by the equipartition theorem. Momenta of atoms are derived by solving Newtons equations with inter-atomic forces derived by Lennard-Jones or L-J potentials. MD implicitly assumes the atom always has heat capacity as otherwise the momenta of the atoms cannot be related to their temperature. In bulk materials, the continuum is simulated by imposing PBC on an ensemble of atoms, the atoms always having heat capacity. PBC stands for periodic boundary conditions. MD simulations of the bulk are therefore valid because atoms in the bulk do indeed have heat capacity. Nanostructures differ. Unlike the continuum, the atom confined in discrete submicron structures is precluded by QM from having the heat capacity necessary to conserve absorbed EM energy by an increase in temperature. QM stands for quantum mechanics and EM for electromagnetic. Quantum corrections of MD solutions that would show the heat capacity of nanostructures vanishes are not performed. What this means is the MD simulations of discrete nanostructures published in the literature not only have no physical meaning, but are knowingly invalid by QM. In the alternative, conservation of absorbed EM energy is proposed to proceed by the creation of QED induced non-thermal EM radiation at the TIR frequency of the nanostructure. QED stands for quantum electrodynamics and TIR for total internal reflection. QED radiation creates excitons (holon and electron pairs) that upon recombination produce EM radiation that charges the nanostructure or is lost to the surroundings a consequence only possible by QM as charge is not created in statistical mechanics. Valid and invalid MD simulations from the literature are illustrated with nanofluids and nanocars, respectively. Finally, valid and invalid MD solutions for the stiffening of NWs in tensile tests are presented to illustrate the unphysical findings if QM is ignored at the nanoscale. NW stands for nanowire.
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Boudjemaa, Abdelaali, Karima Abbas, and Nadia Guebli. "Ultradilute Quantum Droplets in the Presence of Higher-Order Quantum Fluctuations." Atoms 10, no. 2 (June 17, 2022): 64. http://dx.doi.org/10.3390/atoms10020064.
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We investigate the effects of higher-order quantum fluctuations on the bulk properties of self-bound droplets in three-, two- and one-dimensional binary Bose mixtures using the Hartree–Fock–Bogoliubov theory. We calculate higher-order corrections to the equation of state of the droplet at both zero and finite temperatures. We show that our results for the ground-state energy are in a good agreement with recent quantum Monte Carlo simulations in any dimension. Our study extends to the finite temperature case where it is found that thermal fluctuations may destabilize the droplet state and eventually destroy it. In two dimensions, we reveal that the droplet occurs at temperatures well below the Berezinskii–Kosterlitz–Thouless transition temperature.
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Shchesnovich, Valery. "Distinguishing noisy boson sampling from classical simulations." Quantum 5 (March 29, 2021): 423. http://dx.doi.org/10.22331/q-2021-03-29-423.
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Giving a convincing experimental evidence of the quantum supremacy over classical simulations is a challenging goal. Noise is considered to be the main problem in such a demonstration, hence it is urgent to understand the effect of noise. Recently found classical algorithms can efficiently approximate, to any small error, the output of boson sampling with finite-amplitude noise. In this work it is shown analytically and confirmed by numerical simulations that one can efficiently distinguish the output distribution of such a noisy boson sampling from the approximations accounting for low-order quantum multiboson interferences, what includes the mentioned classical algorithms. The number of samples required to tell apart the quantum and classical output distributions is strongly affected by the previously unexplored parameter: density of bosons, i.e., the ratio of total number of interfering bosons to number of input ports of interferometer. Such critical dependence is strikingly reminiscent of the quantum-to-classical transition in systems of identical particles, which sets in when the system size scales up while density of particles vanishes.
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Siberchicot, Bruno, and Jean Clérouin. "An Equation of State of Amorphous β-Boron under High Pressure." Solid State Phenomena 172-174 (June 2011): 1220–21. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.1220.
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Beyond 100 GPa at ambient temperature, β-boron exhibits an amorphization [1]. This paper presents Quantum Molecular Dynamics simulations of the equation of state (EoS) of amorphous boron under pressure.
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Gerodias, Kit M., Maria Victoria Carpio Bernido, and Christopher C. Bernido. "Resonant tunneling in natural photosynthetic systems." Physica Scripta 96, no. 12 (December 1, 2021): 125038. http://dx.doi.org/10.1088/1402-4896/ac3c58.
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Abstract The high internal quantum efficiency observed in higher plants remains an outstanding problem in understanding photosynthesis. Several approaches such as quantum entanglement and quantum coherence have been explored. However, none has yet drawn an analogy between superlattices and the geometrical structure of granal thylakoids in leaves. In this paper, we calculate the transmission coefficients and perform numerical simulations using the parameters relevant to a stack of thylakoid discs. We then show that quantum resonant tunneling can occur at low effective mass of particles for 680 nm and 700 nm incident wavelengths corresponding to energies at which photosynthesis occurs.
Dissertations / Theses on the topic "Physics, Low-Temperature, Quantum Simulations, Atomic Physics"
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MANCINI, MARCO. "Quantum Simulation with Ytterbium Atoms in Synthetic Dimensions." Doctoral thesis, 2016. http://hdl.handle.net/2158/1022296.
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(10726149), Weirong Yuan. "PHASE CHANGE AND ABLATION STUDY OF METALS BY FEMTOSECOND LASER IRRADIATION USING HYBRID TTM/MD SIMULATIONS." Thesis, 2021.
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The interactions of femtosecond lasers with gold targets were investigated with a numerical method combining molecular dynamics (MD) and the two-temperature model (TTM). Previous works using MD-TTM method did not consider all the thermodynamic parameters and the interatomic potential dependent of the electron temperature simultaneously. Therefore, we developed a LAMMPS function to achieve this. To accurately capture the physics behind the interactions, we also included the electron blast force from free electron pressure and the modified Fourier law with steep electron temperature gradient in our model. For bulk materials, a stress non-reflecting and heat conducting boundary is added between the atomistic and the continuum parts. The modified boundary force in our study greatly reduces the reflectivity of the atomistic-continuum boundary compared with its original form. Our model is the first to consider all these factors simultaneously and manage to predict four femtosecond laser ablation phenomena observed in the experiments.
In this dissertation, the thermodynamic parameters in the two-temperature model were extensively explored. We considered three different approaches to calculate these parameters: namely interpolation, ab initio calculation, and analytical expression. We found that simple interpolation between solid state and plasma state could lead to high level of inaccuracy, especially for electron thermal conductivity. Therefore, ab initio calculation and analytical expression were used for the calculation of the thermodynamic parameters in more advanced studies. The effects of electron thermal conductivity and electron-phonon coupling factor on electron and lattice temperatures were analyzed.
Our studies considered electron temperature dependent (ETD) and electron temperature independent (ETI) interatomic potentials. The ETI interatomic potential is easier to implement and therefore it is used in our phase change study to investigate the effects of target thickness on melting. Homogeneous melting occurred for thin films, while melting can be observed through the movement of the solid-liquid interface in thick or bulk materials. However, the ETI potential overestimated the bond strength at high temperatures. Therefore, ablation process was studied with the ETD potential. Three ablation mechanisms were found in our simulations at different laser fluences. Short nonthermal ablation was only observed at the ablation threshold. With increasing laser fluence, spallation was then seen. In high laser fluence regime, phase explosion occurred on the surface and coexisted with spallation.
Lastly, we researched on the effects of the delay time between two femtosecond laser pulses. Various delay times did not have much influence on melting depth. In low laser fluence regime, with increasing delay time, the target went through nonthermal ablation, to spallation and to no ablation. In high laser fluence regime, longer delay time encouraged phase explosion while suppressed spallation.
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ROSI, SARA. "Interacting Bosons in optical lattices: optimal control ground state production, entanglement characterization and 1D systems." Doctoral thesis, 2015. http://hdl.handle.net/2158/1004929.
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The work presented in this thesis concerns the study of quantum many-body physics by making use Bose-Einstein condensates loaded in optical lattices potentials. The first part describes the development of a new experimental strategy for the production of the degenerate atomic sample, the second part concerns the optimal control ground state production and the entanglement characterization on a systems of interacting Bosons across the superfluid - Mott insulator quantum phase transition, and the third part illustrates the study of the dynamical properties of an array of 1D gases performed via Bragg spectroscopy.
Books on the topic "Physics, Low-Temperature, Quantum Simulations, Atomic Physics"
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service), SpringerLink (Online, ed. Quantum Phase Transitions in Cold Atoms and Low Temperature Solids. New York, NY: Springer Science+Business Media, LLC, 2011.
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Hazzard, Kaden Richard Alan. Quantum Phase Transitions in Cold Atoms and Low Temperature Solids. Springer, 2011.
Find full textBook chapters on the topic "Physics, Low-Temperature, Quantum Simulations, Atomic Physics"
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Hazzard, Kaden Richard Alan. "Introduction to Many-Body Physics in Ultracold Atomic Gases." In Quantum Phase Transitions in Cold Atoms and Low Temperature Solids, 1–10. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-8179-0_1.
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Bruder, Lukas, Markus Koch, Marcel Mudrich, and Frank Stienkemeier. "Ultrafast Dynamics in Helium Droplets." In Topics in Applied Physics, 447–511. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-94896-2_10.
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Abstract Helium nanodroplets are peculiar systems, as condensed superfluid entities on the nanoscale, and as vessels for studies of molecules and molecular aggregates and their quantum properties at very low temperature. For both aspects, the dynamics upon the interaction with light is fundamental for understanding the properties of the systems. In this chapter we focus on time-resolved experiments in order to study ultrafast dynamics in neat as well as doped helium nanodroplets. Recent experimental approaches are reviewed, ranging from time-correlated photon detection to femtosecond pump-probe photoelectron and photoion spectroscopy, coherent multidimensional spectroscopy as well as applications of strong laser fields and novel, extreme ultraviolet light sources. The experiments examined in more detail investigate the dynamics of atomic and molecular dopants, including coherent wave packet dynamics and long-lived vibrational coherences of molecules attached to and immersed inside helium droplets. Furthermore, the dynamics of highly-excited helium droplets including interatomic Coulombic decay and nanoplasma states are discussed. Finally, an outlook concludes on the perspectives of time-resolved experiments with helium droplets, including recent options provided by new radiation sources of femto- or even attosecond laser pulses up to the soft X-ray range.
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Merkt, FrÉdÉric. "Molecular-physics aspects of cold chemistry." In Current Trends in Atomic Physics, 82–141. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198837190.003.0003.
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Molecular-physics aspects of cold chemistry are introduced with the example of few-electron molecules. After a brief overview of general aspects of molecular physics, the solution of the molecular Schrödinger equation is presented based on the Born-Oppenheimer approximation and the subsequent evaluation of adiabatic, nonadiabatic, relativistic and radiative (QED) corrections. Low-temperature chemical phenomena are introduced with the example of ion-molecule reactions, using the classical Langevin model for barrier-free exothermic reactions as reference. Then, methods to generate cold few-electron molecules by supersonic-beam-deceleration methods such as Stark, Zeeman, and Rydberg-Stark decelerations are presented. Two astrophysically important reactions, the reaction between H2 and H2+ forming H3+ and H, a very fast reaction following Langevin-capture going over to quantum-Langevin capture at low temperature, and the radiative association reaction H+ + H forming H2+, a very slow reaction in which quantum effects (shape resonances) become important at low temperatures, are used to illustrate the concepts introduced.
Conference papers on the topic "Physics, Low-Temperature, Quantum Simulations, Atomic Physics"
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Prevenslik, Thomas. "Validity of Molecular Dynamics by Quantum Mechanics." In ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/mnhmt2013-22027.
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MD is commonly used in computational physics to determine the atomic response of nanostructures. MD stands for molecular dynamics. With theoretical basis in statistical mechanics, MD relates the thermal energy of the atom to its momentum by the equipartition theorem. Momenta of atoms in an ensemble are determined by solving Newton’s equations with inter-atomic forces derived from Lennard-Jones potentials. MD therefore assumes the atom always has heat capacity as otherwise the momenta of the atoms cannot be related to their temperature. In bulk materials, the continuum is simulated in MD by imposing PBC on an ensemble of atoms, the atoms always having heat capacity. PBC stands for periodic boundary conditions. MD simulations of the bulk are valid because atoms in the bulk do indeed have heat capacity. Nanostructures differ from the bulk. Unlike the continuum, the atom confined in discrete submicron geometries is precluded by QM from having the heat capacity necessary to conserve absorbed EM energy by an increase in temperature. QM stands for quantum mechanics and EM for electromagnetic. Quantum corrections of MD solutions that would show the heat capacity of nanostructures vanishes are not performed. What this means is the MD simulations of discrete nanostructures in the literature not only have no physical meaning, but are knowingly invalid by QM. In the alternative, conservation of absorbed EM energy is proposed to proceed by the creation of QED induced non-thermal EM radiation at the TIR frequency of the nanostructure. QED stands for quantum electrodynamics and TIR for total internal reflection. The QED radiation creates excitons (holon and electron pairs) that upon recombination produce EM radiation that charges the nanostructure or is emitted to the surroundings — a consequence only possible by QM as charge is not created in statistical mechanics. Invalid discrete MD simulations are illustrated with nanofluids, nanocars, linear motors, and sputtering. Finally, a valid MD simulation by QM is presented for the stiffening of NWs in tensile tests. NW stands for nanowire.
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Hess, Harald F. "Near-field optical characterization of quantum wells and nanostructures." In Quantum Optoelectronics. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/qo.1995.qwa2.
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A spatial distribution of luminescent centers with sharp (<0.1meV), spectrally distinct emission lines are revealed in a GaAs/AlGaAs quantum wells[1] using low temperature nearfield scanning optical microscopy [2], a technique where a subwavelength source and/or detector of light in close proximity (<40nm) to the sample is used to probe with a resolution beyond the diffraction limit. These centers are the energy eigenstate components that comprise the inhomogeneously broadened line shape observed in standard far-field photoluminescence. Measurements as a function of temperature, magnetic field, and well width establish that these centers arise from excitons localized by quantum well thickness fluctuations. For sufficiently narrow wells, virtually all emission originates from such centers. Quantities such as diffusion (both thermal and tunneling), lateral confinement energies, lifetimes, g-factors from magnetic field induced spin splittings, diamagnetic energy coefficients of the luminescent states can now be measured at a site-by-site individual quantum level rather than averaged over a statistical distribution. This information can be used in turn to provide a direct local picture of the interface fluctuations and how they vary under different MBE growth conditions. Near-field microscopy/spectroscopy provides a means to access energies and homogeneous line widths for the individual eigenstates of these centers, and thus allows the luminescent components to be identified and characterized with the extraordinary detail previously limited to the realm of atomic physics.
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Nantel, M., T. Buma, J. Workman, A. Maksimchuk, and D. Umstadter. "Continuum lowering in 100-fs laser produced plasmas." In Applications of High Field and Short Wavelength Sources. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/hfsw.1997.thb4.
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We present what we believe to be the first measurements of continuum lowering in high-density plasmas produced by 100-fs laser pulses. Continuum lowering arises in dense plasmas when the excited states of an ion are perturbed by the close proximity of the neighboring ions, and can be a useful density diagnostic. It is a fundamental atomic physics concept in high-density plasmas important to work in X-ray lasers, ICF plasma diagnostics, astrophysics and plasma simulations. In our experiments, a 10-Hz, 100 mJ 100-fs laser system is used to create the plasmas studied, essentially providing a delta-function heat pump which terminates before significant hydrodynamic motion occurs. Continuum lowering was observed both in the high-density, high-temperature expanding plasma plume and in the solid, low-temperature shocked material of the target. In the expanding plasma, we used XUV emission spectroscopy to observe the suppression of high-lying excited levels of He-like and H-like boron. In the compressed plasma behind the shock wave, we used XUV absorption spectroscopy to measure the shifts in inner-shell absorption edges in boron (K-edge) and in aluminium (L-edge).