Direct pair production in heavy-ion--atom collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anholt, R.; Jakubassa-Amundsen, D.H.; Amundsen, P.A.

1983-02-01

Direct pair production in approx.5-MeV/amu heavy-ion--atom collisions with uranium target atoms is calculated with the plane-wave Born approximation and the semiclassical approximation. Briggs's approximation is used to obtain the electron and positron wave functions. Since pair production involves high momentum transfer q from the moving projectile to the vacuum, use is made of a high-q approximation to greatly simplify the numerical computations. Coulomb deflection of the projectile, the effect of finite nuclear size on the elec- tronic wave functions, and the energy loss by the projectile exciting the pair are all taken into account in these calculations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakatsuji, Hiroshi, E-mail: h.nakatsuji@qcri.or.jp; Nakashima, Hiroyuki

The Schrödinger equation (SE) and the antisymmetry principle constitute the governing principle of chemistry. A general method of solving the SE was presented before as the free complement (FC) theory, which gave highly accurate solutions for small atoms and molecules. We assume here to use the FC theory starting from the local valence bond wave function. When this theory is applied to larger molecules, antisymmetrizations of electronic wave functions become time-consuming and therefore, an additional breakthrough is necessary concerning the antisymmetry principle. Usually, in molecular calculations, we first construct the wave function to satisfy the antisymmetry rule, “electronic wave functionsmore » must be prescribed to be antisymmetric for all exchanges of electrons, otherwise bosonic interference may disturb the basis of the science.” Starting from determinantal wave functions is typical. Here, we give an antisymmetrization theory, called inter-exchange (iExg) theory, by dividing molecular antisymmetrizations to those within atoms and between atoms. For the electrons belonging to distant atoms in a molecule, only partial antisymmetrizations or even no antisymmetrizations are necessary, depending on the distance between the atoms. So, the above antisymmetry rule is not necessarily followed strictly to get the results of a desired accuracy. For this and other reasons, the necessary parts of the antisymmetrization operations become very small as molecules become larger, leading finally to the operation counts of lower orders of N, the number of electrons. This theory creates a natural antisymmetrization method that is useful for large molecules.« less

NMR and NQR parameters of ethanol crystal

NASA Astrophysics Data System (ADS)

Milinković, M.; Bilalbegović, G.

2012-04-01

Electric field gradients and chemical shielding tensors of the stable monoclinic crystal phase of ethanol are computed. The projector-augmented wave (PAW) and gauge-including projector-augmented wave (GIPAW) models in the periodic plane-wave density functional theory are used. The crystal data from X-ray measurements, as well as the structures where either all atomic, or only hydrogen atom positions are optimized in the density functional theory are analyzed. These structural models are also studied by including the semi-empirical van der Waals correction to the density functional theory. Infrared spectra of these five crystal models are calculated.

Visualization of a Large Set of Hydrogen Atomic Orbital Contours Using New and Expanded Sets of Parametric Equations

ERIC Educational Resources Information Center

Rhile, Ian J.

2014-01-01

Atomic orbitals are a theme throughout the undergraduate chemistry curriculum, and visualizing them has been a theme in this journal. Contour plots as isosurfaces or contour lines in a plane are the most familiar representations of the hydrogen wave functions. In these representations, a surface of a fixed value of the wave function ? is plotted…

Identification and Characterization of Molecular Bonding Structures by ab initio Quasi-Atomic Orbital Analyses.

PubMed

West, Aaron C; Duchimaza-Heredia, Juan J; Gordon, Mark S; Ruedenberg, Klaus

2017-11-22

The quasi-atomic analysis of ab initio electronic wave functions in full valence spaces, which was developed in preceding papers, yields oriented quasi-atomic orbitals in terms of which the ab initio molecular wave function and energy can be expressed. These oriented quasi-atomic orbitals are the rigorous ab initio counterparts to the conceptual bond forming atomic hybrid orbitals of qualitative chemical reasoning. In the present work, the quasi-atomic orbitals are identified as bonding orbitals, lone pair orbitals, radical orbitals, vacant orbitals and orbitals with intermediate character. A program determines the bonding characteristics of all quasi-atomic orbitals in a molecule on the basis of their occupations, bond orders, kinetic bond orders, hybridizations and local symmetries. These data are collected in a record and provide the information for a comprehensive understanding of the synergism that generates the bonding structure that holds the molecule together. Applications to a series of molecules exhibit the complete bonding structures that are embedded in their ab initio wave functions. For the strong bonds in a molecule, the quasi-atomic orbitals provide quantitative ab initio amplifications of the Lewis dot symbols. Beyond characterizing strong bonds, the quasi-atomic analysis also yields an understanding of the weak interactions, such as vicinal, hyperconjugative and radical stabilizations, which can make substantial contributions to the molecular bonding structure.

Introduction to Density Functional Theory: Calculations by Hand on the Helium Atom

ERIC Educational Resources Information Center

Baseden, Kyle A.; Tye, Jesse W.

2014-01-01

Density functional theory (DFT) is a type of electronic structure calculation that has rapidly gained popularity. In this article, we provide a step-by-step demonstration of a DFT calculation by hand on the helium atom using Slater's X-Alpha exchange functional on a single Gaussian-type orbital to represent the atomic wave function. This DFT…

Semiclassical approach to atomic decoherence by gravitational waves

NASA Astrophysics Data System (ADS)

Quiñones, D. A.; Varcoe, B. T. H.

2018-01-01

A new heuristic model of interaction of an atomic system with a gravitational wave (GW) is proposed. In it, the GW alters the local electromagnetic field of the atomic nucleus, as perceived by the electron, changing the state of the system. The spectral decomposition of the wave function is calculated, from which the energy is obtained. The results suggest a shift in the difference of the atomic energy levels, which will induce a small detuning to a resonant transition. The detuning increases with the quantum numbers of the levels, making the effect more prominent for Rydberg states. We performed calculations on the Rabi oscillations of atomic transitions, estimating how they would vary as a result of the proposed effect.

A projection-free method for representing plane-wave DFT results in an atom-centered basis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunnington, Benjamin D.; Schmidt, J. R., E-mail: schmidt@chem.wisc.edu

2015-09-14

Plane wave density functional theory (DFT) is a powerful tool for gaining accurate, atomic level insight into bulk and surface structures. Yet, the delocalized nature of the plane wave basis set hinders the application of many powerful post-computation analysis approaches, many of which rely on localized atom-centered basis sets. Traditionally, this gap has been bridged via projection-based techniques from a plane wave to atom-centered basis. We instead propose an alternative projection-free approach utilizing direct calculation of matrix elements of the converged plane wave DFT Hamiltonian in an atom-centered basis. This projection-free approach yields a number of compelling advantages, including strictmore » orthonormality of the resulting bands without artificial band mixing and access to the Hamiltonian matrix elements, while faithfully preserving the underlying DFT band structure. The resulting atomic orbital representation of the Kohn-Sham wavefunction and Hamiltonian provides a gateway to a wide variety of analysis approaches. We demonstrate the utility of the approach for a diverse set of chemical systems and example analysis approaches.« less

On the importance of local orbitals using second energy derivatives for d and f electrons

NASA Astrophysics Data System (ADS)

Karsai, Ferenc; Tran, Fabien; Blaha, Peter

2017-11-01

The all-electron linearized augmented plane wave (LAPW) methods are among the most accurate to solve the Kohn-Sham equations of density functional theory for periodic solids. In the LAPW methods, the unit cell is partitioned into spheres surrounding the atoms, inside which the wave functions are expanded into spherical harmonics, and the interstitial region, where the wave functions are expanded in Fourier series. Recently, Michalicek et al. (2013) reported an analysis of the so-called linearization error, which is inherent to the basis functions inside the spheres, and advocated the use of local orbital basis functions involving the second energy derivative of the radial part (HDLO). In the present work, we report the implementation of such basis functions into the WIEN2k code, and discuss in detail the improvement in terms of accuracy. From our tests, which involve atoms from the whole periodic table, it is concluded that for ground-state properties (e.g., equilibrium volume) the use of HDLO is necessary only for atoms with d or f electrons in the valence and large atomic spheres. For unoccupied states which are not too high above the Fermi energy, HDLO systematically improve the band structure, which may be of importance for the calculation of optical properties.

Electron number probability distributions for correlated wave functions.

PubMed

Francisco, E; Martín Pendás, A; Blanco, M A

2007-03-07

Efficient formulas for computing the probability of finding exactly an integer number of electrons in an arbitrarily chosen volume are only known for single-determinant wave functions [E. Cances et al., Theor. Chem. Acc. 111, 373 (2004)]. In this article, an algebraic method is presented that extends these formulas to the case of multideterminant wave functions and any number of disjoint volumes. The derived expressions are applied to compute the probabilities within the atomic domains derived from the space partitioning based on the quantum theory of atoms in molecules. Results for a series of test molecules are presented, paying particular attention to the effects of electron correlation and of some numerical approximations on the computed probabilities.

Dependence of the atomic level Green-Kubo stress correlation function on wavevector and frequency: molecular dynamics results from a model liquid.

PubMed

Levashov, V A

2014-09-28

We report on a further investigation of a new method that can be used to address vibrational dynamics and propagation of stress waves in liquids. The method is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the atomic level stress correlation functions. This decomposition, as was demonstrated previously for a model liquid studied in molecular dynamics simulations, reveals the presence of stress waves propagating over large distances and a structure that resembles the pair density function. In this paper, by performing the Fourier transforms of the atomic level stress correlation functions, we elucidate how the lifetimes of the stress waves and the ranges of their propagation depend on their frequency, wavevector, and temperature. These results relate frequency and wavevector dependence of the generalized viscosity to the character of propagation of the shear stress waves. In particular, the results suggest that an increase in the value of the frequency dependent viscosity at low frequencies with decrease of temperature is related to the increase in the ranges of propagation of the stress waves of the corresponding low frequencies. We found that the ranges of propagation of the shear stress waves of frequencies less than half of the Einstein frequency extend well beyond the nearest neighbor shell even above the melting temperature. The results also show that the crossover from quasilocalized to propagating behavior occurs at frequencies usually associated with the Boson peak.

Atomic spectroscopy with twisted photons: Separation of M 1 -E 2 mixed multipoles

NASA Astrophysics Data System (ADS)

Afanasev, Andrei; Carlson, Carl E.; Solyanik, Maria

2018-02-01

We analyze atomic photoexcitation into the discrete states by twisted photons, or photons carrying extra orbital angular momentum along their direction of propagation. From the angular momentum and parity considerations, we are able to relate twisted-photon photoexcitation amplitudes to their plane-wave analogs, independently of the details of the atomic wave functions. We analyze the photoabsorption cross sections of mixed-multipolarity E 2 -M 1 transitions in ionized atoms and found fundamental differences coming from the photon topology. Our theoretical analysis demonstrates that it is possible to extract the relative transition rates of different multipolar contributions by measuring the photoexcitation rate as a function of the atom's position (or impact parameter) with respect to the optical vortex center. The proposed technique for separation of multipoles can be implemented if the target's atom position is resolved with subwavelength accuracy; for example, with Paul traps. Numerical examples are presented for Boron-like highly charged ions.

Theoretical atomic physics code development I: CATS: Cowan Atomic Structure Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdallah, J. Jr.; Clark, R.E.H.; Cowan, R.D.

An adaptation of R.D. Cowan's Atomic Structure program, CATS, has been developed as part of the Theoretical Atomic Physics (TAPS) code development effort at Los Alamos. CATS has been designed to be easy to run and to produce data files that can interface with other programs easily. The CATS produced data files currently include wave functions, energy levels, oscillator strengths, plane-wave-Born electron-ion collision strengths, photoionization cross sections, and a variety of other quantities. This paper describes the use of CATS. 10 refs.

Parity-violating electric-dipole transitions in helium

NASA Technical Reports Server (NTRS)

Hiller, J.; Sucher, J.; Bhatia, A. K.; Feinberg, G.

1980-01-01

The paper examines parity-violating electric-dipole transitions in He in order to gain insight into the reliability of approximate calculations which are carried out for transitions in many-electron atoms. The contributions of the nearest-lying states are computed with a variety of wave functions, including very simple product wave functions, Hartree-Fock functions and Hylleraas-type wave functions with up to 84 parameters. It is found that values of the matrix elements of the parity-violating interaction can differ considerably from the values obtained from the good wave functions, even when these simple wave functions give accurate values for the matrix elements in question

Two-photon excitation cross section in light and intermediate atoms in frozen-core LS-coupling approximation

NASA Technical Reports Server (NTRS)

Omidvar, K.

1980-01-01

Using the method of explicit summation over the intermediate states two-photon absorption cross sections in light and intermediate atoms based on the simplistic frozen-core approximation and LS coupling have been formulated. Formulas for the cross section in terms of integrals over radial wave functions are given. Two selection rules, one exact and one approximate, valid within the stated approximations are derived. The formulas are applied to two-photon absorptions in nitrogen, oxygen, and chlorine. In evaluating the radial integrals, for low-lying levels, the Hartree-Fock wave functions, and for high-lying levels, hydrogenic wave functions obtained by the quantum-defect method have been used. A relationship between the cross section and the oscillator strengths is derived.

Photoelectron wave function in photoionization: plane wave or Coulomb wave?

PubMed

Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

2015-11-19

The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.

Ionizing gas breakdown waves in strong electric fields.

NASA Technical Reports Server (NTRS)

Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

1972-01-01

A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

Atomic collisions in the presence of laser radiation - Time dependence and the asymptotic wave function

NASA Technical Reports Server (NTRS)

Devries, P. L.; George, T. F.

1982-01-01

A time-dependent, wave-packet description of atomic collisions in the presence of laser radiation is extracted from the more conventional time-independent, stationary-state description. This approach resolves certain difficulties of interpretation in the time-independent approach which arise in the case of asymptotic near resonance. In the two-state model investigated, the approach predicts the existence of three spherically scattered waves in this asymptotically near-resonant case.

Analysis of STM images with pure and CO-functionalized tips: A first-principles and experimental study

NASA Astrophysics Data System (ADS)

Gustafsson, Alexander; Okabayashi, Norio; Peronio, Angelo; Giessibl, Franz J.; Paulsson, Magnus

2017-08-01

We describe a first-principles method to calculate scanning tunneling microscopy (STM) images, and compare the results to well-characterized experiments combining STM with atomic force microscopy (AFM). The theory is based on density functional theory with a localized basis set, where the wave functions in the vacuum gap are computed by propagating the localized-basis wave functions into the gap using a real-space grid. Constant-height STM images are computed using Bardeen's approximation method, including averaging over the reciprocal space. We consider copper adatoms and single CO molecules adsorbed on Cu(111), scanned with a single-atom copper tip with and without CO functionalization. The calculated images agree with state-of-the-art experiments, where the atomic structure of the tip apex is determined by AFM. The comparison further allows for detailed interpretation of the STM images.

Wave-packet continuum-discretization approach to ion-atom collisions including rearrangement: Application to differential ionization in proton-hydrogen scattering

NASA Astrophysics Data System (ADS)

Abdurakhmanov, I. B.; Bailey, J. J.; Kadyrov, A. S.; Bray, I.

2018-03-01

In this work, we develop a wave-packet continuum-discretization approach to ion-atom collisions that includes rearrangement processes. The total scattering wave function is expanded using a two-center basis built from wave-packet pseudostates. The exact three-body Schrödinger equation is converted into coupled-channel differential equations for time-dependent expansion coefficients. In the asymptotic region these time-dependent coefficients represent transition amplitudes for all processes including elastic scattering, excitation, ionization, and electron capture. The wave-packet continuum-discretization approach is ideal for differential ionization studies as it allows one to generate pseudostates with arbitrary energies and distribution. The approach is used to calculate the double differential cross section for ionization in proton collisions with atomic hydrogen. Overall good agreement with experiment is obtained for all considered cases.

Distinguishing between evidence and its explanations in the steering of atomic clocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myers, John M., E-mail: myers@seas.harvard.edu; Hadi Madjid, F., E-mail: gmadjid@aol.com

2014-11-15

Quantum theory reflects within itself a separation of evidence from explanations. This separation leads to a known proof that: (1) no wave function can be determined uniquely by evidence, and (2) any chosen wave function requires a guess reaching beyond logic to things unforeseeable. Chosen wave functions are encoded into computer-mediated feedback essential to atomic clocks, including clocks that step computers through their phases of computation and clocks in space vehicles that supply evidence of signal propagation explained by hypotheses of spacetimes with metric tensor fields. The propagation of logical symbols from one computer to another requires a shared rhythm—likemore » a bucket brigade. Here we show how hypothesized metric tensors, dependent on guesswork, take part in the logical synchronization by which clocks are steered in rate and position toward aiming points that satisfy phase constraints, thereby linking the physics of signal propagation with the sharing of logical symbols among computers. Recognizing the dependence of the phasing of symbol arrivals on guesses about signal propagation transports logical synchronization from the engineering of digital communications to a discipline essential to physics. Within this discipline we begin to explore questions invisible under any concept of time that fails to acknowledge unforeseeable events. In particular, variation of spacetime curvature is shown to limit the bit rate of logical communication. - Highlights: • Atomic clocks are steered in frequency toward an aiming point. • The aiming point depends on a chosen wave function. • No evidence alone can determine the wave function. • The unknowability of the wave function has implications for spacetime curvature. • Variability in spacetime curvature limits the bit rate of communications.« less

Kinetic energy partition method applied to ground state helium-like atoms.

PubMed

Chen, Yu-Hsin; Chao, Sheng D

2017-03-28

We have used the recently developed kinetic energy partition (KEP) method to solve the quantum eigenvalue problems for helium-like atoms and obtain precise ground state energies and wave-functions. The key to treating properly the electron-electron (repulsive) Coulomb potential energies for the KEP method to be applied is to introduce a "negative mass" term into the partitioned kinetic energy. A Hartree-like product wave-function from the subsystem wave-functions is used to form the initial trial function, and the variational search for the optimized adiabatic parameters leads to a precise ground state energy. This new approach sheds new light on the all-important problem of solving many-electron Schrödinger equations and hopefully opens a new way to predictive quantum chemistry. The results presented here give very promising evidence that an effective one-electron model can be used to represent a many-electron system, in the spirit of density functional theory.

Ab initio study of the electrostatic multipole nature of torsional potentials in CH3SSCH3, CH3SSH, and HOOH

NASA Technical Reports Server (NTRS)

Sokalski, W. A.; Lai, J.; Luo, N.; Sun, S.; Shibata, M.; Ornstein, R.; Rein, R.

1991-01-01

The origin of torsional potentials in H3CSSCH3, H3CSSH, and HOOH and the anisotropy of the local charge distribution has been analyzed in terms of atomic multipoles calculated from the ab initio LCAO-MO-SCF wave function in the 6-31G* basis set. The results indicate that for longer -S-S-bonds the major contribution to these torsional barriers are electrostatic interactions of the atomic multipoles located on two atoms forming the rotated bond. This finding demonstrates the important role of electrostatic 1-2 interatomic interactions, usually neglected in conformational studies. It also opens the possibility to derive directly from accurate ab initio wave functions a simple nonempirical torsional potential involving atomic multipoles of two bonded atoms defining the torsional angle. For shorter -O-O- bonds, use of more precise models and inclusion of 1-3 interactions seems to be necessary.

Photoelectron wave function in photoionization: Plane wave or Coulomb wave? [Does photoionization of neutral targets produce Coulomb or plane waves?

DOE PAGES

Gozem, Samer; Gunina, Anastasia O.; Ichino, Takatoshi; ...

2015-10-28

The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectronmore » wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. Finally, the results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.« less

Properties of atomic pairs produced in the collision of Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Ziń, Paweł; Wasak, Tomasz

2018-04-01

During a collision of Bose-Einstein condensates correlated pairs of atoms are emitted. The scattered massive particles, in analogy to photon pairs in quantum optics, might be used in the violation of Bell's inequalities, demonstration of Einstein-Podolsky-Rosen correlations, or sub-shot-noise atomic interferometry. Usually, a theoretical description of the collision relies either on stochastic numerical methods or on analytical treatments involving various approximations. Here, we investigate elastic scattering of atoms from colliding elongated Bose-Einstein condensates within the Bogoliubov method, carefully controlling performed approximations at every stage of the analysis. We derive expressions for the one- and two-particle correlation functions. The obtained formulas, which relate the correlation functions to the condensate wave function, are convenient for numerical calculations. We employ the variational approach for condensate wave functions to obtain analytical expressions for the correlation functions, whose properties we analyze in detail. We also present a useful semiclassical model of the process and compare its results with the quantum one. The results are relevant for recent experiments with excited helium atoms, as well as for planned experiments aimed at investigating the nonclassicality of the system.

Hartree-Fock implementation using a Laguerre-based wave function for the ground state and correlation energies of two-electron atoms.

PubMed

King, Andrew W; Baskerville, Adam L; Cox, Hazel

2018-03-13

An implementation of the Hartree-Fock (HF) method using a Laguerre-based wave function is described and used to accurately study the ground state of two-electron atoms in the fixed nucleus approximation, and by comparison with fully correlated (FC) energies, used to determine accurate electron correlation energies. A variational parameter A is included in the wave function and is shown to rapidly increase the convergence of the energy. The one-electron integrals are solved by series solution and an analytical form is found for the two-electron integrals. This methodology is used to produce accurate wave functions, energies and expectation values for the helium isoelectronic sequence, including at low nuclear charge just prior to electron detachment. Additionally, the critical nuclear charge for binding two electrons within the HF approach is calculated and determined to be Z HF C =1.031 177 528.This article is part of the theme issue 'Modern theoretical chemistry'. © 2018 The Author(s).

Discovery of a general method of solving the Schrödinger and dirac equations that opens a way to accurately predictive quantum chemistry.

PubMed

Nakatsuji, Hiroshi

2012-09-18

Just as Newtonian law governs classical physics, the Schrödinger equation (SE) and the relativistic Dirac equation (DE) rule the world of chemistry. So, if we can solve these equations accurately, we can use computation to predict chemistry precisely. However, for approximately 80 years after the discovery of these equations, chemists believed that they could not solve SE and DE for atoms and molecules that included many electrons. This Account reviews ideas developed over the past decade to further the goal of predictive quantum chemistry. Between 2000 and 2005, I discovered a general method of solving the SE and DE accurately. As a first inspiration, I formulated the structure of the exact wave function of the SE in a compact mathematical form. The explicit inclusion of the exact wave function's structure within the variational space allows for the calculation of the exact wave function as a solution of the variational method. Although this process sounds almost impossible, it is indeed possible, and I have published several formulations and applied them to solve the full configuration interaction (CI) with a very small number of variables. However, when I examined analytical solutions for atoms and molecules, the Hamiltonian integrals in their secular equations diverged. This singularity problem occurred in all atoms and molecules because it originates from the singularity of the Coulomb potential in their Hamiltonians. To overcome this problem, I first introduced the inverse SE and then the scaled SE. The latter simpler idea led to immediate and surprisingly accurate solution for the SEs of the hydrogen atom, helium atom, and hydrogen molecule. The free complement (FC) method, also called the free iterative CI (free ICI) method, was efficient for solving the SEs. In the FC method, the basis functions that span the exact wave function are produced by the Hamiltonian of the system and the zeroth-order wave function. These basis functions are called complement functions because they are the elements of the complete functions for the system under consideration. We extended this idea to solve the relativistic DE and applied it to the hydrogen and helium atoms, without observing any problems such as variational collapse. Thereafter, we obtained very accurate solutions of the SE for the ground and excited states of the Born-Oppenheimer (BO) and non-BO states of very small systems like He, H(2)(+), H(2), and their analogues. For larger systems, however, the overlap and Hamiltonian integrals over the complement functions are not always known mathematically (integration difficulty); therefore we formulated the local SE (LSE) method as an integral-free method. Without any integration, the LSE method gave fairly accurate energies and wave functions for small atoms and molecules. We also calculated continuous potential curves of the ground and excited states of small diatomic molecules by introducing the transferable local sampling method. Although the FC-LSE method is simple, the achievement of chemical accuracy in the absolute energy of larger systems remains time-consuming. The development of more efficient methods for the calculations of ordinary molecules would allow researchers to make these calculations more easily.

QEDMOD: Fortran program for calculating the model Lamb-shift operator

NASA Astrophysics Data System (ADS)

Shabaev, V. M.; Tupitsyn, I. I.; Yerokhin, V. A.

2018-02-01

We present Fortran package QEDMOD for computing the model QED operator hQED that can be used to account for the Lamb shift in accurate atomic-structure calculations. The package routines calculate the matrix elements of hQED with the user-specified one-electron wave functions. The operator can be used to calculate Lamb shift in many-electron atomic systems with a typical accuracy of few percent, either by evaluating the matrix element of hQED with the many-electron wave function, or by adding hQED to the Dirac-Coulomb-Breit Hamiltonian.

Quantum principle of sensing gravitational waves: From the zero-point fluctuations to the cosmological stochastic background of spacetime

NASA Astrophysics Data System (ADS)

Quiñones, Diego A.; Oniga, Teodora; Varcoe, Benjamin T. H.; Wang, Charles H.-T.

2017-08-01

We carry out a theoretical investigation on the collective dynamics of an ensemble of correlated atoms, subject to both vacuum fluctuations of spacetime and stochastic gravitational waves. A general approach is taken with the derivation of a quantum master equation capable of describing arbitrary confined nonrelativistic matter systems in an open quantum gravitational environment. It enables us to relate the spectral function for gravitational waves and the distribution function for quantum gravitational fluctuations and to indeed introduce a new spectral function for the zero-point fluctuations of spacetime. The formulation is applied to two-level identical bosonic atoms in an off-resonant high-Q cavity that effectively inhibits undesirable electromagnetic delays, leading to a gravitational transition mechanism through certain quadrupole moment operators. The overall relaxation rate before reaching equilibrium is found to generally scale collectively with the number N of atoms. However, we are also able to identify certain states of which the decay and excitation rates with stochastic gravitational waves and vacuum spacetime fluctuations amplify more significantly with a factor of N2. Using such favorable states as a means of measuring both conventional stochastic gravitational waves and novel zero-point spacetime fluctuations, we determine the theoretical lower bounds for the respective spectral functions. Finally, we discuss the implications of our findings on future observations of gravitational waves of a wider spectral window than currently accessible. Especially, the possible sensing of the zero-point fluctuations of spacetime could provide an opportunity to generate initial evidence and further guidance of quantum gravity.

Detailed Wave Function Analysis for Multireference Methods: Implementation in the Molcas Program Package and Applications to Tetracene.

PubMed

Plasser, Felix; Mewes, Stefanie A; Dreuw, Andreas; González, Leticia

2017-11-14

High-level multireference computations on electronically excited and charged states of tetracene are performed, and the results are analyzed using an extensive wave function analysis toolbox that has been newly implemented in the Molcas program package. Aside from verifying the strong effect of dynamic correlation, this study reveals an unexpected critical influence of the atomic orbital basis set. It is shown that different polarized double-ζ basis sets produce significantly different results for energies, densities, and overall wave functions, with the best performance obtained for the atomic natural orbital (ANO) basis set by Pierloot et al. Strikingly, the ANO basis set not only reproduces the energies but also performs exceptionally well in terms of describing the diffuseness of the different states and of their attachment/detachment densities. This study, thus, not only underlines the fact that diffuse basis functions are needed for an accurate description of the electronic wave functions but also shows that, at least for the present example, it is enough to include them implicitly in the contraction scheme.

Localized spatially nonlinear matter waves in atomic-molecular Bose-Einstein condensates with space-modulated nonlinearity

PubMed Central

Yao, Yu-Qin; Li, Ji; Han, Wei; Wang, Deng-Shan; Liu, Wu-Ming

2016-01-01

The intrinsic nonlinearity is the most remarkable characteristic of the Bose-Einstein condensates (BECs) systems. Many studies have been done on atomic BECs with time- and space- modulated nonlinearities, while there is few work considering the atomic-molecular BECs with space-modulated nonlinearities. Here, we obtain two kinds of Jacobi elliptic solutions and a family of rational solutions of the atomic-molecular BECs with trapping potential and space-modulated nonlinearity and consider the effect of three-body interaction on the localized matter wave solutions. The topological properties of the localized nonlinear matter wave for no coupling are analysed: the parity of nonlinear matter wave functions depends only on the principal quantum number n, and the numbers of the density packets for each quantum state depend on both the principal quantum number n and the secondary quantum number l. When the coupling is not zero, the localized nonlinear matter waves given by the rational function, their topological properties are independent of the principal quantum number n, only depend on the secondary quantum number l. The Raman detuning and the chemical potential can change the number and the shape of the density packets. The stability of the Jacobi elliptic solutions depends on the principal quantum number n, while the stability of the rational solutions depends on the chemical potential and Raman detuning. PMID:27403634

Efficient and Flexible Computation of Many-Electron Wave Function Overlaps.

PubMed

Plasser, Felix; Ruckenbauer, Matthias; Mai, Sebastian; Oppel, Markus; Marquetand, Philipp; González, Leticia

2016-03-08

A new algorithm for the computation of the overlap between many-electron wave functions is described. This algorithm allows for the extensive use of recurring intermediates and thus provides high computational efficiency. Because of the general formalism employed, overlaps can be computed for varying wave function types, molecular orbitals, basis sets, and molecular geometries. This paves the way for efficiently computing nonadiabatic interaction terms for dynamics simulations. In addition, other application areas can be envisaged, such as the comparison of wave functions constructed at different levels of theory. Aside from explaining the algorithm and evaluating the performance, a detailed analysis of the numerical stability of wave function overlaps is carried out, and strategies for overcoming potential severe pitfalls due to displaced atoms and truncated wave functions are presented.

Stark effect on an excited hydrogen atom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barratt, C.

1983-07-01

The method of degenerate perturbation theory is used to study the dipolar nature of an excited hydrogen atom in an external electric field. The dependence of the atoms perturbed energy levels on the principal and magnetic quantum numbers, n and m, is investigated, along with the perturbed wave functions.

How Accurately Does the Free Complement Wave Function of a Helium Atom Satisfy the Schroedinger Equation?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakashima, Hiroyuki; Nakatsuji, Hiroshi

2008-12-12

The local energy defined by H{psi}/{psi} must be equal to the exact energy E at any coordinate of an atom or molecule, as long as the {psi} under consideration is exact. The discrepancy from E of this quantity is a stringent test of the accuracy of the calculated wave function. The H-square error for a normalized {psi}, defined by {sigma}{sup 2}{identical_to}<{psi}|(H-E){sup 2}|{psi}>, is also a severe test of the accuracy. Using these quantities, we have examined the accuracy of our wave function of a helium atom calculated using the free complement method that was developed to solve the Schroedinger equation.more » Together with the variational upper bound, the lower bound of the exact energy calculated using a modified Temple's formula ensured the definitely correct value of the helium fixed-nucleus ground state energy to be -2.903 724 377 034 119 598 311 159 245 194 4 a.u., which is correct to 32 digits.« less

Logical synchronization: how evidence and hypotheses steer atomic clocks

NASA Astrophysics Data System (ADS)

Myers, John M.; Madjid, F. Hadi

2014-05-01

A clock steps a computer through a cycle of phases. For the propagation of logical symbols from one computer to another, each computer must mesh its phases with arrivals of symbols from other computers. Even the best atomic clocks drift unforeseeably in frequency and phase; feedback steers them toward aiming points that depend on a chosen wave function and on hypotheses about signal propagation. A wave function, always under-determined by evidence, requires a guess. Guessed wave functions are coded into computers that steer atomic clocks in frequency and position—clocks that step computers through their phases of computations, as well as clocks, some on space vehicles, that supply evidence of the propagation of signals. Recognizing the dependence of the phasing of symbol arrivals on guesses about signal propagation elevates `logical synchronization.' from its practice in computer engineering to a dicipline essential to physics. Within this discipline we begin to explore questions invisible under any concept of time that fails to acknowledge the unforeseeable. In particular, variation of spacetime curvature is shown to limit the bit rate of logical communication.

Wave-function functionals

NASA Astrophysics Data System (ADS)

Pan, Xiao-Yin; Slamet, Marlina; Sahni, Viraht

2010-04-01

We extend our prior work on the construction of variational wave functions ψ that are functionals of functions χ:ψ=ψ[χ] rather than simply being functions. In this manner, the space of variations is expanded over those of traditional variational wave functions. In this article we perform the constrained search over the functions χ chosen such that the functional ψ[χ] satisfies simultaneously the constraints of normalization and the exact expectation value of an arbitrary single- or two-particle Hermitian operator, while also leading to a rigorous upper bound to the energy. As such the wave function functional is accurate not only in the region of space in which the principal contributions to the energy arise but also in the other region of the space represented by the Hermitian operator. To demonstrate the efficacy of these ideas, we apply such a constrained search to the ground state of the negative ion of atomic hydrogen H-, the helium atom He, and its positive ions Li+ and Be2+. The operators W whose expectations are obtained exactly are the sum of the single-particle operators W=∑irin,n=-2,-1,1,2, W=∑iδ(ri), W=-(1)/(2)∑i∇i2, and the two-particle operators W=∑nun,n=-2,-1,1,2, where u=|ri-rj|. Comparisons with the method of Lagrangian multipliers and of other constructions of wave-function functionals are made. Finally, we present further insights into the construction of wave-function functionals by studying a previously proposed construction of functionals ψ[χ] that lead to the exact expectation of arbitrary Hermitian operators. We discover that analogous to the solutions of the Schrödinger equation, there exist ψ[χ] that are unphysical in that they lead to singular values for the expectations. We also explain the origin of the singularity.

Huygens-Fresnel picture for electron-molecule elastic scattering★

NASA Astrophysics Data System (ADS)

Baltenkov, Arkadiy S.; Msezane, Alfred Z.

2017-11-01

The elastic scattering cross sections for a slow electron by C2 and H2 molecules have been calculated within the framework of the non-overlapping atomic potential model. For the amplitudes of the multiple electron scattering by a target the wave function of the molecular continuum is represented as a combination of a plane wave and two spherical waves generated by the centers of atomic spheres. This wave function obeys the Huygens-Fresnel principle according to which the electron wave scattering by a system of two centers is accompanied by generation of two spherical waves; their interaction creates a diffraction pattern far from the target. Each of the Huygens waves, in turn, is a superposition of the partial spherical waves with different orbital angular momenta l and their projections m. The amplitudes of these partial waves are defined by the corresponding phases of electron elastic scattering by an isolated atomic potential. In numerical calculations the s- and p-phase shifts are taken into account. So the number of interfering electron waves is equal to eight: two of which are the s-type waves and the remaining six waves are of the p-type with different m values. The calculation of the scattering amplitudes in closed form (rather than in the form of S-matrix expansion) is reduced to solving a system of eight inhomogeneous algebraic equations. The differential and total cross sections of electron scattering by fixed-in-space molecules and randomly oriented ones have been calculated as well. We conclude by discussing the special features of the S-matrix method for the case of arbitrary non-spherical potentials. Contribution to the Topical Issue "Low energy positron and electron interactions", edited by James Sullivan, Ron White, Michael Bromley, Ilya Fabrikant, and David Cassidy.

Ab Initio Vibrational Levels For HO2 and Vibrational Splittings for Hydrogen Atom Transfer

NASA Technical Reports Server (NTRS)

Barclay, V. J.; Dateo, Christopher E.; Hamilton, I. P.; Arnold, James O. (Technical Monitor)

1994-01-01

We calculate vibrational levels and wave functions for HO2 using the recently reported ab initio potential energy surface of Walch and Duchovic. There is intramolecular hydrogen atom transfer when the hydrogen atom tunnels through a T-shaped saddle point separating two equivalent equilibrium geometries, and correspondingly, the energy levels are split. We focus on vibrational levels and wave functions with significant splitting. The first three vibrational levels with splitting greater than 2/cm are (15 0), (0 7 1) and (0 8 0) where V(sub 2) is the O-O-H bend quantum number. We discuss the dynamics of hydrogen atom transfer; in particular, the O-O distances at which hydrogen atom transfer is most probable for these vibrational levels. The material of the proposed presentation was reviewed and the technical content will not reveal any information not already in the public domain and will not give any foreign industry or government a competitive advantage.

Quantum Chemistry on Quantum Computers: A Polynomial-Time Quantum Algorithm for Constructing the Wave Functions of Open-Shell Molecules.

PubMed

Sugisaki, Kenji; Yamamoto, Satoru; Nakazawa, Shigeaki; Toyota, Kazuo; Sato, Kazunobu; Shiomi, Daisuke; Takui, Takeji

2016-08-18

Quantum computers are capable to efficiently perform full configuration interaction (FCI) calculations of atoms and molecules by using the quantum phase estimation (QPE) algorithm. Because the success probability of the QPE depends on the overlap between approximate and exact wave functions, efficient methods to prepare accurate initial guess wave functions enough to have sufficiently large overlap with the exact ones are highly desired. Here, we propose a quantum algorithm to construct the wave function consisting of one configuration state function, which is suitable for the initial guess wave function in QPE-based FCI calculations of open-shell molecules, based on the addition theorem of angular momentum. The proposed quantum algorithm enables us to prepare the wave function consisting of an exponential number of Slater determinants only by a polynomial number of quantum operations.

Calculation of total electron excitation cross-sections and partial electron ionization cross-sections for the elements. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Green, T. J.

1973-01-01

Computer programs were used to calculate the total electron excitation cross-section for atoms and the partial ionization cross-section. The approximations to the scattering amplitude used are as follows: (1) Born, Bethe, and Modified Bethe for non-exchange excitation; (2) Ochkur for exchange excitation; and (3) Coulomb-Born of non-exchange ionization. The amplitudes are related to the differential cross-sections which are integrated to give the total excitation (or partial ionization) cross-section for the collision. The atomic wave functions used are Hartree-Fock-Slater functions for bound states and the coulomb wave function for the continuum. The programs are presented and the results are examined.

Automatic software correction of residual aberrations in reconstructed HRTEM exit waves of crystalline samples

DOE PAGES

Ophus, Colin; Rasool, Haider I.; Linck, Martin; ...

2016-11-30

We develop an automatic and objective method to measure and correct residual aberrations in atomic-resolution HRTEM complex exit waves for crystalline samples aligned along a low-index zone axis. Our method uses the approximate rotational point symmetry of a column of atoms or single atom to iteratively calculate a best-fit numerical phase plate for this symmetry condition, and does not require information about the sample thickness or precise structure. We apply our method to two experimental focal series reconstructions, imaging a β-Si 3N 4 wedge with O and N doping, and a single-layer graphene grain boundary. We use peak and latticemore » fitting to evaluate the precision of the corrected exit waves. We also apply our method to the exit wave of a Si wedge retrieved by off-axis electron holography. In all cases, the software correction of the residual aberration function improves the accuracy of the measured exit waves.« less

Automatic software correction of residual aberrations in reconstructed HRTEM exit waves of crystalline samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ophus, Colin; Rasool, Haider I.; Linck, Martin

We develop an automatic and objective method to measure and correct residual aberrations in atomic-resolution HRTEM complex exit waves for crystalline samples aligned along a low-index zone axis. Our method uses the approximate rotational point symmetry of a column of atoms or single atom to iteratively calculate a best-fit numerical phase plate for this symmetry condition, and does not require information about the sample thickness or precise structure. We apply our method to two experimental focal series reconstructions, imaging a β-Si 3N 4 wedge with O and N doping, and a single-layer graphene grain boundary. We use peak and latticemore » fitting to evaluate the precision of the corrected exit waves. We also apply our method to the exit wave of a Si wedge retrieved by off-axis electron holography. In all cases, the software correction of the residual aberration function improves the accuracy of the measured exit waves.« less

Introduction to the Contributions of A. Temkin and R. J. Drachman to Atomic Physics

NASA Technical Reports Server (NTRS)

Bhatia, A.K.

2007-01-01

Their work, as is the work of most atomic theorists, is concerned with solving the Schroedinger equation accurately for wave function in cases where there is no exact analytical solution. In particular, Temkin is associated with electron scattering from atoms and ions. When he started there already were a number of methods to study the scattering of electrons from atoms.

Infinite Multiplets

DOE R&D Accomplishments Database

Nambu, Y.

1967-01-01

The main ingredients of the method of infinite multiplets consist of: 1) the use of wave functions with an infinite number of components for describing an infinite tower of discrete states of an isolated system (such as an atom, a nucleus, or a hadron), 2) the use of group theory, instead of dynamical considerations, in determining the properties of the wave functions.

Controlled rephasing of single spin-waves in a quantum memory based on cold atoms

NASA Astrophysics Data System (ADS)

Farrera, Pau; Albrecht, Boris; Heinze, Georg; Cristiani, Matteo; de Riedmatten, Hugues; Quantum Photonics With Solids; Atoms Team

2015-05-01

Quantum memories for light allow a reversible transfer of quantum information between photons and long lived matter quantum bits. In atomic ensembles, this information is commonly stored in the form of single collective spin excitations (spin-waves). In this work we demonstrate that we can actively control the dephasing of the spin-waves created in a quantum memory based on a cold Rb87 atomic ensemble. The control is provided by an external magnetic field gradient, which induces an inhomogeneous broadening of the atomic hyperfine levels. We show that acting on this gradient allows to control the dephasing of individual spin-waves and to induce later a rephasing. The spin-waves are then mapped into single photons, and we demonstrate experimentally that the active rephasing preserves the sub-Poissonian statistics of the retrieved photons. Finally we show that this rephasing control enables the creation and storage of multiple spin-waves in different temporal modes, which can be selectively readout. This is an important step towards the implementation of a functional temporally multiplexed quantum memory for quantum repeaters. We acknowledge support from the ERC starting grant, the Spanish Ministry of Economy and Competitiveness, the Fondo Europeo de Desarrollo Regional, and the International PhD- fellowship program ``la Caixa''-Severo Ochoa @ICFO.

Inhibition of quantum transport due to 'scars' of unstable periodic orbits

NASA Technical Reports Server (NTRS)

Jensen, R. V.; Sanders, M. M.; Saraceno, M.; Sundaram, B.

1989-01-01

A new quantum mechanism for the suppression of chaotic ionization of highly excited hydrogen atoms explains the appearance of anomalously stable states in the microwave ionization experiments of Koch et al. A novel phase-space representation of the perturbed wave functions reveals that the inhibition of quantum transport is due to the selective excitation of wave functions that are highly localized near unstable periodic orbits in the chaotic classical phase space. The 'scarred' wave functions provide a new basis for the quantum description of a variety of classically chaotic systems.

Absolute Scale Quantitative Off-Axis Electron Holography at Atomic Resolution

NASA Astrophysics Data System (ADS)

Winkler, Florian; Barthel, Juri; Tavabi, Amir H.; Borghardt, Sven; Kardynal, Beata E.; Dunin-Borkowski, Rafal E.

2018-04-01

An absolute scale match between experiment and simulation in atomic-resolution off-axis electron holography is demonstrated, with unknown experimental parameters determined directly from the recorded electron wave function using an automated numerical algorithm. We show that the local thickness and tilt of a pristine thin WSe2 flake can be measured uniquely, whereas some electron optical aberrations cannot be determined unambiguously for a periodic object. The ability to determine local specimen and imaging parameters directly from electron wave functions is of great importance for quantitative studies of electrostatic potentials in nanoscale materials, in particular when performing in situ experiments and considering that aberrations change over time.

General properties of quantum optical systems in a strong field limit

NASA Technical Reports Server (NTRS)

Chumakov, S. M.; Klimov, Andrei B.

1994-01-01

We investigate the dynamics of an arbitrary atomic system (n-level atoms or many n-level atoms) interacting with a resonant quantized mode of an em field. If the initial field state is a coherent state with a large photon number then the system dynamics possesses some general features, independently of the particular structure of the atomic system. Namely, trapping states, factorization of the wave function, collapses and revivals of the atomic energy oscillations are discussed.

Understanding the atomic-level Green-Kubo stress correlation function for a liquid through phonons in a model crystal

NASA Astrophysics Data System (ADS)

Levashov, V. A.

2014-11-01

In order to gain insight into the connection between the vibrational dynamics and the atomic-level Green-Kubo stress correlation function in liquids, we consider this connection in a model crystal instead. Of course, vibrational dynamics in liquids and crystals are quite different and it is not expected that the results obtained on a model crystal should be valid for liquids. However, these considerations provide a benchmark to which the results of the previous molecular dynamics simulations can be compared. Thus, assuming that vibrations are plane waves, we derive analytical expressions for the atomic-level stress correlation functions in the classical limit and analyze them. These results provide, in particular, a recipe for analysis of the atomic-level stress correlation functions in Fourier space and extraction of the wave-vector and frequency-dependent information. We also evaluate the energies of the atomic-level stresses. The energies obtained are significantly smaller than the energies previously determined in molecular dynamics simulations of several model liquids. This result suggests that the average energies of the atomic-level stresses in liquids and glasses are largely determined by the structural disorder. We discuss this result in the context of equipartition of the atomic-level stress energies. Analysis of the previously published data suggests that it is possible to speak about configurational and vibrational contributions to the average energies of the atomic-level stresses in a glass state. However, this separation in a liquid state is problematic. We also introduce and briefly consider the atomic-level transverse current correlation function. Finally, we address the broadening of the peaks in the pair distribution function with increase of distance. We find that the peaks' broadening (by ≈40 % ) occurs due to the transverse vibrational modes, while contribution from the longitudinal modes does not change with distance.

A complete active space valence bond method with nonorthogonal orbitals

NASA Astrophysics Data System (ADS)

Hirao, Kimihiko; Nakano, Haruyuki; Nakayama, Kenichi

1997-12-01

A complete active space self-consistent field (SCF) wave function is transformed into a valence bond type representation built from nonorthogonal orbitals, each strongly localized on a single atom. Nonorthogonal complete active space SCF orbitals are constructed by Ruedenberg's projected localization procedure so that they have maximal overlaps with the corresponding minimum basis set of atomic orbitals of the free-atoms. The valence bond structures which are composed of such nonorthogonal quasiatomic orbitals constitute the wave function closest to the concept of the oldest and most simple valence bond method. The method is applied to benzene, butadiene, hydrogen, and methane molecules and compared to the previously proposed complete active space valence bond approach with orthogonal orbitals. The results demonstrate the validity of the method as a powerful tool for describing the electronic structure of various molecules.

The Dynamics of a Five-level (Double Λ)-type Atom Interacting with Two-mode Field in a Cross Kerr-like Medium

NASA Astrophysics Data System (ADS)

Obada, A.-S. F.; Ahmed, M. M. A.; Farouk, Ahmed M.

2018-04-01

In this paper, we propose a new transition scheme (Double Λ) for the interaction between a five-level atom and an electromagnetic field and study its dynamics in the presence of a cross Kerr-like medium in the exact-resonance case. The wave function is derived when the atom is initially prepared in its upper most state, and the field is initially prepared in the coherent state. We studied the atomic population inversion, the coherence degree by studying the second-order correlation function, Cauchy-Schwartz inequality (CSI) and the relation with P-function. Finally, we investigate the effect of Kerr-like medium on the evolution of Husimi Q-function of the considered system.

Determination of wave-function functionals: The constrained-search variational method

NASA Astrophysics Data System (ADS)

Pan, Xiao-Yin; Sahni, Viraht; Massa, Lou

2005-09-01

In a recent paper [Phys. Rev. Lett. 93, 130401 (2004)], we proposed the idea of expanding the space of variations in variational calculations of the energy by considering the approximate wave function ψ to be a functional of functions χ , ψ=ψ[χ] , rather than a function. A constrained search is first performed over all functions χ such that the wave-function functional ψ[χ] satisfies a physical constraint or leads to the known value of an observable. A rigorous upper bound to the energy is then obtained via the variational principle. In this paper we generalize the constrained-search variational method, applicable to both ground and excited states, to the determination of arbitrary Hermitian single-particle operators as applied to two-electron atomic and ionic systems. We construct analytical three-parameter ground-state functionals for the H- ion and the He atom through the constraint of normalization. We present the results for the total energy E , the expectations of the single-particle operators W=∑irin , n=-2,-1,1,2 , W=∑iδ(ri) , and W=∑iδ(ri-r) , the structure of the nonlocal Coulomb hole charge ρc(rr') , and the expectations of the two particle operators u2,u,1/u,1/u2 , where u=∣ri-rj∣ . The results for all the expectation values are remarkably accurate when compared with the 1078-parameter wave function of Pekeris, and other wave functions that are not functionals. We conclude by describing our current work on how the constrained-search variational method in conjunction with quantal density-functional theory is being applied to the many-electron case.

Anomalous diffusion in a dynamical optical lattice

NASA Astrophysics Data System (ADS)

Zheng, Wei; Cooper, Nigel R.

2018-02-01

Motivated by experimental progress in strongly coupled atom-photon systems in optical cavities, we study theoretically the quantum dynamics of atoms coupled to a one-dimensional dynamical optical lattice. The dynamical lattice is chosen to have a period that is incommensurate with that of an underlying static lattice, leading to a dynamical version of the Aubry-André model which can cause localization of single-particle wave functions. We show that atomic wave packets in this dynamical lattice generically spread via anomalous diffusion, which can be tuned between superdiffusive and subdiffusive regimes. This anomalous diffusion arises from an interplay between Anderson localization and quantum fluctuations of the cavity field.

Sensitivity function analysis of gravitational wave detection with single-laser and large-momentum-transfer atomic sensors

NASA Astrophysics Data System (ADS)

Tang, Biao; Zhang, Bao-Cheng; Zhou, Lin; Wang, Jin; Zhan, Ming-Sheng

2015-03-01

Recently, a configuration using atomic interferometers (AIs) had been suggested for the detection of gravitational waves. A new AI with some additional laser pulses for implementing large momentum transfer was also put forward, in order to reduce the effect of shot noise and laser frequency noise. We use a sensitivity function to analyze all possible configurations of the new AI and to distinguish how many momenta are transferred in a specific configuration. By analyzing the new configuration, we further explore a detection scheme for gravitational waves, in particular, that ameliorates laser frequency noise. We find that the amelioration occurs in such a scheme, but novelly, in some cases, the frequency noise can be canceled completely by using a proper data processing method. Supported by the National Natural Science Foundation of China.

Atom Interferometry for Fundamental Physics and Gravity Measurements in Space

NASA Technical Reports Server (NTRS)

Kohel, James M.

2012-01-01

Laser-cooled atoms are used as freefall test masses. The gravitational acceleration on atoms is measured by atom-wave interferometry. The fundamental concept behind atom interferometry is the quantum mechanical particle-wave duality. One can exploit the wave-like nature of atoms to construct an atom interferometer based on matter waves analogous to laser interferometers.

Correlation in photon pairs generated using four-wave mixing in a cold atomic ensemble

NASA Astrophysics Data System (ADS)

Ferdinand, Andrew Richard; Manjavacas, Alejandro; Becerra, Francisco Elohim

2017-04-01

Spontaneous four-wave mixing (FWM) in atomic ensembles can be used to generate narrowband entangled photon pairs at or near atomic resonances. While extensive research has been done to investigate the quantum correlations in the time and polarization of such photon pairs, the study and control of high dimensional quantum correlations contained in their spatial degrees of freedom has not been fully explored. In our work we experimentally investigate the generation of correlated light from FWM in a cold ensemble of cesium atoms as a function of the frequencies of the pump fields in the FWM process. In addition, we theoretically study the spatial correlations of the photon pairs generated in the FWM process, specifically the joint distribution of their orbital angular momentum (OAM). We investigate the width of the distribution of the OAM modes, known as the spiral bandwidth, and the purity of OAM correlations as a function of the properties of the pump fields, collected photons, and the atomic ensemble. These studies will guide experiments involving high dimensional entanglement of photons generated from this FWM process and OAM-based quantum communication with atomic ensembles. This work is supported by AFORS Grant FA9550-14-1-0300.

Adiabatic corrections to density functional theory energies and wave functions.

PubMed

Mohallem, José R; Coura, Thiago de O; Diniz, Leonardo G; de Castro, Gustavo; Assafrão, Denise; Heine, Thomas

2008-09-25

The adiabatic finite-nuclear-mass-correction (FNMC) to the electronic energies and wave functions of atoms and molecules is formulated for density-functional theory and implemented in the deMon code. The approach is tested for a series of local and gradient corrected density functionals, using MP2 results and diagonal-Born-Oppenheimer corrections from the literature for comparison. In the evaluation of absolute energy corrections of nonorganic molecules the LDA PZ81 functional works surprisingly better than the others. For organic molecules the GGA BLYP functional has the best performance. FNMC with GGA functionals, mainly BLYP, show a good performance in the evaluation of relative corrections, except for nonorganic molecules containing H atoms. The PW86 functional stands out with the best evaluation of the barrier of linearity of H2O and the isotopic dipole moment of HDO. In general, DFT functionals display an accuracy superior than the common belief and because the corrections are based on a change of the electronic kinetic energy they are here ranked in a new appropriate way. The approach is applied to obtain the adiabatic correction for full atomization of alcanes C(n)H(2n+2), n = 4-10. The barrier of 1 mHartree is approached for adiabatic corrections, justifying its insertion into DFT.

Rydberg Molecules for Ion-Atom Scattering in the Ultracold Regime

NASA Astrophysics Data System (ADS)

Schmid, T.; Veit, C.; Zuber, N.; Löw, R.; Pfau, T.; Tarana, M.; Tomza, M.

2018-04-01

We propose a novel experimental method to extend the investigation of ion-atom collisions from the so far studied cold, essentially classical regime to the ultracold, quantum regime. The key aspect of this method is the use of Rydberg molecules to initialize the ultracold ion-atom scattering event. We exemplify the proposed method with the lithium ion-atom system, for which we present simulations of how the initial Rydberg molecule wave function, freed by photoionization, evolves in the presence of the ion-atom scattering potential. We predict bounds for the ion-atom scattering length from ab initio calculations of the interaction potential. We demonstrate that, in the predicted bounds, the scattering length can be experimentally determined from the velocity of the scattered wave packet in the case of 6Li+ = 6Li and from the molecular ion fraction in the case of 7Li+ - 7Li. The proposed method to utilize Rydberg molecules for ultracold ion-atom scattering, here particularized for the lithium ion-atom system, is readily applicable to other ion-atom systems as well.

Rydberg Molecules for Ion-Atom Scattering in the Ultracold Regime.

PubMed

Schmid, T; Veit, C; Zuber, N; Löw, R; Pfau, T; Tarana, M; Tomza, M

2018-04-13

We propose a novel experimental method to extend the investigation of ion-atom collisions from the so far studied cold, essentially classical regime to the ultracold, quantum regime. The key aspect of this method is the use of Rydberg molecules to initialize the ultracold ion-atom scattering event. We exemplify the proposed method with the lithium ion-atom system, for which we present simulations of how the initial Rydberg molecule wave function, freed by photoionization, evolves in the presence of the ion-atom scattering potential. We predict bounds for the ion-atom scattering length from ab initio calculations of the interaction potential. We demonstrate that, in the predicted bounds, the scattering length can be experimentally determined from the velocity of the scattered wave packet in the case of ^{6}Li^{+}-^{6}Li and from the molecular ion fraction in the case of ^{7}Li^{+}-^{7}Li. The proposed method to utilize Rydberg molecules for ultracold ion-atom scattering, here particularized for the lithium ion-atom system, is readily applicable to other ion-atom systems as well.

The two-electron atomic systems. S-states

NASA Astrophysics Data System (ADS)

Liverts, Evgeny Z.; Barnea, Nir

2010-01-01

A simple Mathematica program for computing the S-state energies and wave functions of two-electron (helium-like) atoms (ions) is presented. The well-known method of projecting the Schrödinger equation onto the finite subspace of basis functions was applied. The basis functions are composed of the exponentials combined with integer powers of the simplest perimetric coordinates. No special subroutines were used, only built-in objects supported by Mathematica. The accuracy of results and computation time depend on the basis size. The precise energy values of 7-8 significant figures along with the corresponding wave functions can be computed on a single processor within a few minutes. The resultant wave functions have a simple analytical form consisting of elementary functions, that enables one to calculate the expectation values of arbitrary physical operators without any difficulties. Program summaryProgram title: TwoElAtom-S Catalogue identifier: AEFK_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFK_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 10 185 No. of bytes in distributed program, including test data, etc.: 495 164 Distribution format: tar.gz Programming language: Mathematica 6.0; 7.0 Computer: Any PC Operating system: Any which supports Mathematica; tested under Microsoft Windows XP and Linux SUSE 11.0 RAM:⩾10 bytes Classification: 2.1, 2.2, 2.7, 2.9 Nature of problem: The Schrödinger equation for atoms (ions) with more than one electron has not been solved analytically. Approximate methods must be applied in order to obtain the wave functions or other physical attributes from quantum mechanical calculations. Solution method: The S-wave function is expanded into a triple basis set in three perimetric coordinates. Method of projecting the two-electron Schrödinger equation (for atoms/ions) onto a subspace of the basis functions enables one to obtain the set of homogeneous linear equations F.C=0 for the coefficients C of the above expansion. The roots of equation det(F)=0 yield the bound energies. Restrictions: First, the too large length of expansion (basis size) takes the too large computation time giving no perceptible improvement in accuracy. Second, the order of polynomial Ω (input parameter) in the wave function expansion enables one to calculate the excited nS-states up to n=Ω+1 inclusive. Additional comments: The CPC Program Library includes "A program to calculate the eigenfunctions of the random phase approximation for two electron systems" (AAJD). It should be emphasized that this fortran code realizes a very rough approximation describing only the averaged electron density of the two electron systems. It does not characterize the properties of the individual electrons and has a number of input parameters including the Roothaan orbitals. Running time: ˜10 minutes (depends on basis size and computer speed)

MEASUREMENT OF FREE AIR ATOMIC BLAST PRESSURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haskell, N.A.; Fava, J.A.; Brubaker, R.M.

1958-02-14

BS>Peak free-air overpressure versus time measurements in the 10-to-2 psi range were obtained as a function of distance directly over a nuclear burst at a low scaled height. This information was to be used to establish the points in space at which the reflected and direct shock waves merge into a single shock wave and to determine the overpressure as a function of distance for the merged wave, in support of drone-aircraft lethal-volume studies. It was also desired to obtain free air peak overpressure versus distance measurements for an atomic burst at a high altitude. Data are tabulated that weremore » obtained by deploying, from a B-29 aircraft, 10 parachute-borne instrumented canisters on each shot. The second objective was achieved by deploying 15 parachute-borne canisters from the strike aircraft on one shot. (C.H.)« less

Observation of the Anderson metal-insulator transition with atomic matter waves: Theory and experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemarie, Gabriel; Delande, Dominique; Chabe, Julien

Using a cold atomic gas exposed to laser pulses - a realization of the chaotic quasiperiodic kicked rotor with three incommensurate frequencies - we study experimentally and theoretically the Anderson metal-insulator transition in three dimensions. Sensitive measurements of the atomic wave function and the use of finite-size scaling techniques make it possible to unambiguously demonstrate the existence of a quantum phase transition and to measure its critical exponents. By taking proper account of systematic corrections to one-parameter scaling, we show the universality of the critical exponent {nu}=1.59{+-}0.01, which is found to be equal to the one previously computed for themore » Anderson model.« less

Bose-Einstein condensation in microgravity.

PubMed

van Zoest, T; Gaaloul, N; Singh, Y; Ahlers, H; Herr, W; Seidel, S T; Ertmer, W; Rasel, E; Eckart, M; Kajari, E; Arnold, S; Nandi, G; Schleich, W P; Walser, R; Vogel, A; Sengstock, K; Bongs, K; Lewoczko-Adamczyk, W; Schiemangk, M; Schuldt, T; Peters, A; Könemann, T; Müntinga, H; Lämmerzahl, C; Dittus, H; Steinmetz, T; Hänsch, T W; Reichel, J

2010-06-18

Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.

Simple and efficient LCAO basis sets for the diffuse states in carbon nanostructures.

PubMed

Papior, Nick R; Calogero, Gaetano; Brandbyge, Mads

2018-06-27

We present a simple way to describe the lowest unoccupied diffuse states in carbon nanostructures in density functional theory calculations using a minimal LCAO (linear combination of atomic orbitals) basis set. By comparing plane wave basis calculations, we show how these states can be captured by adding long-range orbitals to the standard LCAO basis sets for the extreme cases of planar sp 2 (graphene) and curved carbon (C 60 ). In particular, using Bessel functions with a long range as additional basis functions retain a minimal basis size. This provides a smaller and simpler atom-centered basis set compared to the standard pseudo-atomic orbitals (PAOs) with multiple polarization orbitals or by adding non-atom-centered states to the basis.

Simple and efficient LCAO basis sets for the diffuse states in carbon nanostructures

NASA Astrophysics Data System (ADS)

Papior, Nick R.; Calogero, Gaetano; Brandbyge, Mads

2018-06-01

We present a simple way to describe the lowest unoccupied diffuse states in carbon nanostructures in density functional theory calculations using a minimal LCAO (linear combination of atomic orbitals) basis set. By comparing plane wave basis calculations, we show how these states can be captured by adding long-range orbitals to the standard LCAO basis sets for the extreme cases of planar sp 2 (graphene) and curved carbon (C60). In particular, using Bessel functions with a long range as additional basis functions retain a minimal basis size. This provides a smaller and simpler atom-centered basis set compared to the standard pseudo-atomic orbitals (PAOs) with multiple polarization orbitals or by adding non-atom-centered states to the basis.

Scattering from Artificial Piezoelectriclike Meta-Atoms and Molecules

NASA Astrophysics Data System (ADS)

Goltcman, Leonid; Hadad, Yakir

2018-01-01

Inspired by natural piezoelectricity, we introduce hybrid-wave electromechanical meta-atoms and metamolecules that consist of coupled electrical and mechanical oscillators with similar resonance frequencies. We explore the linearized electromechanical scattering process and demonstrate that by exploiting the hybrid-wave interaction one may enable functionalities that are forbidden otherwise. For example, we study a dimer metamolecule that is highly directional for electromagnetic waves, although it is electrically deep subwavelength. This unique behavior is a consequence of the fact that, while the metamolecule is electrically small, it is acoustically large. This idea opens vistas for a plethora of exciting dynamics and phenomena in electromagnetics and acoustics, with implications for miniaturized sensors, superresolution imaging, compact nonreciprocal antennas, and more.

Shock Waves in a Bose-Einstein Condensate

NASA Technical Reports Server (NTRS)

Kulikov, Igor; Zak, Michail

2005-01-01

A paper presents a theoretical study of shock waves in a trapped Bose-Einstein condensate (BEC). The mathematical model of the BEC in this study is a nonlinear Schroedinger equation (NLSE) in which (1) the role of the wave function of a single particle in the traditional Schroedinger equation is played by a space- and time-dependent complex order parameter (x,t) proportional to the square root of the density of atoms and (2) the atoms engage in a repulsive interaction characterized by a potential proportional to | (x,t)|2. Equations that describe macroscopic perturbations of the BEC at zero temperature are derived from the NLSE and simplifying assumptions are made, leading to equations for the propagation of sound waves and the transformation of sound waves into shock waves. Equations for the speeds of shock waves and the relationships between jumps of velocity and density across shock fronts are derived. Similarities and differences between this theory and the classical theory of sound waves and shocks in ordinary gases are noted. The present theory is illustrated by solving the equations for the example of a shock wave propagating in a cigar-shaped BEC.

Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1986-01-01

The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis.

PubMed

Gustafsson, Alexander; Paulsson, Magnus

2017-12-20

We present a method used to intuitively interpret the scanning tunneling microscopy (STM) contrast by investigating individual wave functions originating from the substrate and tip side. We use localized basis orbital density functional theory, and propagate the wave functions into the vacuum region at a real-space grid, including averaging over the lateral reciprocal space. Optimization by means of the method of Lagrange multipliers is implemented to perform a unitary transformation of the wave functions in the middle of the vacuum region. The method enables (i) reduction of the number of contributing tip-substrate wave function combinations used in the corresponding transmission matrix, and (ii) to bundle up wave functions with similar symmetry in the lateral plane, so that (iii) an intuitive understanding of the STM contrast can be achieved. The theory is applied to a CO dimer adsorbed on a Cu(1 1 1) surface scanned by a single-atom Cu tip, whose STM image is discussed in detail by the outlined method.

STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis

NASA Astrophysics Data System (ADS)

Gustafsson, Alexander; Paulsson, Magnus

2017-12-01

We present a method used to intuitively interpret the scanning tunneling microscopy (STM) contrast by investigating individual wave functions originating from the substrate and tip side. We use localized basis orbital density functional theory, and propagate the wave functions into the vacuum region at a real-space grid, including averaging over the lateral reciprocal space. Optimization by means of the method of Lagrange multipliers is implemented to perform a unitary transformation of the wave functions in the middle of the vacuum region. The method enables (i) reduction of the number of contributing tip-substrate wave function combinations used in the corresponding transmission matrix, and (ii) to bundle up wave functions with similar symmetry in the lateral plane, so that (iii) an intuitive understanding of the STM contrast can be achieved. The theory is applied to a CO dimer adsorbed on a Cu(1 1 1) surface scanned by a single-atom Cu tip, whose STM image is discussed in detail by the outlined method.

A "Bit" of Quantum Mechanics

ERIC Educational Resources Information Center

Oss, Stefano; Rosi, Tommaso

2015-01-01

We have developed an app for iOS-based smart-phones/tablets that allows a 3-D, complex phase-based colorful visualization of hydrogen atom wave functions. Several important features of the quantum behavior of atomic orbitals can easily be made evident, thus making this app a useful companion in introductory modern physics classes. There are many…

The physical basis for absorption of light. [effects on wave functions of gas molecules and atoms

NASA Technical Reports Server (NTRS)

Pickett, H. M.

1979-01-01

The effects of light absorption on the wave functions of gas-phase molecules and atoms are investigated by high resolution spectral measurements of radiation emerging from a sample. A Stark-modulated sample of methyl fluoride was irradiated at the 102 GHz rotational transition and the emergent radiation was resolved by means of a spectrum analyzer. For signal oscillator frequencies below or above the molecular resonance by one modulation frequency, the amplitudes of the upper and lower modulation sidebands are found to be of nonuniform intensity, which is inconsistent with amplitude modulation. Emission due to polarization is, however, calculated to be consistent with the results observed, indicating that light absorption should be considered as a subtractive stimulated emission.

Microhartree precision in density functional theory calculations

NASA Astrophysics Data System (ADS)

Gulans, Andris; Kozhevnikov, Anton; Draxl, Claudia

2018-04-01

To address ultimate precision in density functional theory calculations we employ the full-potential linearized augmented plane-wave + local-orbital (LAPW + lo) method and justify its usage as a benchmark method. LAPW + lo and two completely unrelated numerical approaches, the multiresolution analysis (MRA) and the linear combination of atomic orbitals, yield total energies of atoms with mean deviations of 0.9 and 0.2 μ Ha , respectively. Spectacular agreement with the MRA is reached also for total and atomization energies of the G2-1 set consisting of 55 molecules. With the example of α iron we demonstrate the capability of LAPW + lo to reach μ Ha /atom precision also for periodic systems, which allows also for the distinction between the numerical precision and the accuracy of a given functional.

Multi-hump potentials for efficient wave absorption in the numerical solution of the time-dependent Schrödinger equation

NASA Astrophysics Data System (ADS)

Silaev, A. A.; Romanov, A. A.; Vvedenskii, N. V.

2018-03-01

In the numerical solution of the time-dependent Schrödinger equation by grid methods, an important problem is the reflection and wrap-around of the wave packets at the grid boundaries. Non-optimal absorption of the wave function leads to possible large artifacts in the results of numerical simulations. We propose a new method for the construction of the complex absorbing potentials for wave suppression at the grid boundaries. The method is based on the use of the multi-hump imaginary potential which contains a sequence of smooth and symmetric humps whose widths and amplitudes are optimized for wave absorption in different spectral intervals. We show that this can ensure a high efficiency of absorption in a wide range of de Broglie wavelengths, which includes wavelengths comparable to the width of the absorbing layer. Therefore, this method can be used for high-precision simulations of various phenomena where strong spreading of the wave function takes place, including the phenomena accompanying the interaction of strong fields with atoms and molecules. The efficiency of the proposed method is demonstrated in the calculation of the spectrum of high-order harmonics generated during the interaction of hydrogen atoms with an intense infrared laser pulse.

Thomson scattering in the average-atom approximation.

PubMed

Johnson, W R; Nilsen, J; Cheng, K T

2012-09-01

The average-atom model is applied to study Thomson scattering of x-rays from warm dense matter with emphasis on scattering by bound electrons. Parameters needed to evaluate the dynamic structure function (chemical potential, average ionic charge, free electron density, bound and continuum wave functions, and occupation numbers) are obtained from the average-atom model. The resulting analysis provides a relatively simple diagnostic for use in connection with x-ray scattering measurements. Applications are given to dense hydrogen, beryllium, aluminum, and titanium plasmas. In the case of titanium, bound states are predicted to modify the spectrum significantly.

Frequency and Wavevector Dependence of the Atomic Level Stress-Stress Correlation Function in a Model Supercooled Liquid

NASA Astrophysics Data System (ADS)

Levashov, Valentin A.; Morris, James R.; Egami, Takeshi

2012-02-01

Temporal and spatial correlations among the local atomic level shear stresses were studied for a model liquid iron by molecular dynamics simulation [PRL 106,115703]. Integration over time and space of the shear stress correlation function F(r,t) yields viscosity via Green-Kubo relation. The stress correlation function in time and space F(r,t) was Fourier transformed to study the dependence on frequency, E, and wave vector, Q. The results, F(Q,E), showed damped shear stress waves propagating in the liquid for small Q at high and low temperatures. We also observed additional diffuse feature that appears as temperature is reduced below crossover temperature of potential energy landscape at relatively low frequencies at small Q. We suggest that this additional feature might be related to dynamic heterogeneity and boson peaks. We also discuss a relation between the time-scale of the stress-stress correlation function and the alpha-relaxation time of the intermediate self-scattering function S(Q,E).

Potential surfaces for O atom-polymer reactions

NASA Technical Reports Server (NTRS)

Laskowski, B. C.; Jaffe, R. L.

1987-01-01

Ab initio quantum chemistry methods are used to study the energetics of interactions of O atoms with organic compounds. Polyethylene (CH2)n has been chosen as the model system to study the interactions of O(3P) and O(1D) atoms with polymers. In particular, H abstraction is investigated and polyethylene is represented by a C3 (propane) oligomeric model. The gradient method, as implemented in the GRADSCF package of programs, is used to determine the geometries and energies of products and reactants. The saddle point, barrier geometry is determined by minimizing the squares of the gradients of the potential with respect to the internal coordinates. To correctly describe the change in bonding during the reaction at least a two configuration MCSCF (multiconfiguration self consistent field) or GVB (generalized valence bond) wave function has to be used. Basis sets include standard Pople and Dunning sets, however, increased with polarization functions and diffuse p functions on both the C and O atoms. The latter is important due to the O(-) character of the wave function at the saddle point and products. Normal modes and vibrational energy levels are given for the reactants, saddle points and products. Finally, quantitative energetics are obtained by implementing a small CAS (complete active space) approach followed by limited configuration interaction (CI) calculations. Comparisons are made with available experimental data.

Possibility to Probe Negative Values of a Wigner Function in Scattering of a Coherent Superposition of Electronic Wave Packets by Atoms.

PubMed

Karlovets, Dmitry V; Serbo, Valeriy G

2017-10-27

Within a plane-wave approximation in scattering, an incoming wave packet's Wigner function stays positive everywhere, which obscures such purely quantum phenomena as nonlocality and entanglement. With the advent of the electron microscopes with subnanometer-sized beams, one can enter a genuinely quantum regime where the latter effects become only moderately attenuated. Here we show how to probe negative values of the Wigner function in scattering of a coherent superposition of two Gaussian packets with a nonvanishing impact parameter between them (a Schrödinger's cat state) by atomic targets. For hydrogen in the ground 1s state, a small parameter of the problem, a ratio a/σ_{⊥} of the Bohr radius a to the beam width σ_{⊥}, is no longer vanishing. We predict an azimuthal asymmetry of the scattered electrons, which is found to be up to 10%, and argue that it can be reliably detected. The production of beams with the not-everywhere-positive Wigner functions and the probing of such quantum effects can open new perspectives for noninvasive electron microscopy, quantum tomography, particle physics, and so forth.

Completeness of the Coulomb Wave Functions in Quantum Mechanics

ERIC Educational Resources Information Center

Mukunda, N.

1978-01-01

Gives an explicit and elementary proof that the radial energy eigenfunctions for the hydrogen atom in quantum mechanics, bound and scattering states included, form a complete set. The proof uses some properties of the confluent hypergeometric functions and the Cauchy residue theorem from analytic function theory. (Author/GA)

Shock wave loading of a magnetic guide

NASA Astrophysics Data System (ADS)

Kindt, L.

2011-10-01

The atom laser has long been a holy grail within atom physics and with the creation of an atom laser we hope to bring a similar revolution in to the field of atom optics. With the creation of the Bose-Einstein Condensate (BEC) in 1995 the path to an atom laser was initiated. An atom laser is continues source of BEC. In a Bose condensate all the atoms occupy the same quantum state and can be described by the same wave function and phase. With an atom laser the De Broglie wavelength of atoms can be much smaller than the wavelength of light. Due to the ultimate control over the atoms the atom laser is very interesting for atom optics, lithography, metrology, etching and deposition of atoms on a surface. All previous atom lasers have been created from atoms coupled out from an existing Bose-Einstein Condensate. There are different approaches but common to them all is that the duration of the output of the atom laser is limited by the size of the initial BEC and they all have a low flux. This leaves the quest to build a continuous high flux atom laser. An alternative approach to a continuous BEC beam is to channel a continuous ultra cold atomic beam into a magnetic guide and then cool this beam down to degeneracy. Cooling down a continuous beam of atoms faces three large problems: The collision rate has to be large enough for effective rethermalization, since evaporative cooling in 2D is not as effective as in 3D and a large thermal conductivity due to atoms with a high angular momentum causes heating downstream in the guide. We have built a 4 meter magnetic guide that is placed on a downward slope with a magnetic barrier in the end. In the guide we load packets of ultra cold rubidium atoms with a frequency rate large enough for the packets to merge together to form a continuous atomic beam. The atomic beam is supersonic and when the beam reaches the end barrier it will return and collide with itself. The collisions lowers the velocity of the beam into subsonic velocities and a shock wave is created between the two velocity regions. In order to conserve number of particle, momentum and enthalpy the density of the atomic beam passing through the shock wave must increase. We have build such a shock wave in an atomic beam and observed the density increase due to this. As an extra feature having a subsonic beam on a downward slope adds an extra density increase due to gravitational compression. Loading ultra cold atoms into a 3D trap from the dense subsonic beam overcomes the problem with 2D cooling and thermal conductivity. This was done and evaporative cooling was applied creating an unprecedented large number rubidium BEC.

Intrinsic Atomic Orbitals: An Unbiased Bridge between Quantum Theory and Chemical Concepts.

PubMed

Knizia, Gerald

2013-11-12

Modern quantum chemistry can make quantitative predictions on an immense array of chemical systems. However, the interpretation of those predictions is often complicated by the complex wave function expansions used. Here we show that an exceptionally simple algebraic construction allows for defining atomic core and valence orbitals, polarized by the molecular environment, which can exactly represent self-consistent field wave functions. This construction provides an unbiased and direct connection between quantum chemistry and empirical chemical concepts, and can be used, for example, to calculate the nature of bonding in molecules, in chemical terms, from first principles. In particular, we find consistency with electronegativities (χ), C 1s core-level shifts, resonance substituent parameters (σR), Lewis structures, and oxidation states of transition-metal complexes.

Calculation of the total electron excitation cross section in the Born approximation using Slater wave functions for the Li (2s yields 2p), Li (2s yields 3p), Na (3s yields 4p), Mg (3p yields 4s), Ca (4s yields 4p) and K (4s yields 4p) excitations. M.S. Thesis

NASA Technical Reports Server (NTRS)

Simsic, P. L.

1974-01-01

Excitation of neutral atoms by inelastic scattering of incident electrons in gaseous nebulae were investigated using Slater Wave functions to describe the initial and final states of the atom. Total cross sections using the Born Approximation are calculated for: Li(2s yields 2p), Na(3s yields 4p), k(4s yields 4p). The intensity of emitted radiation from gaseous nebulae is also calculated, and Maxwell distribution is employed to average the kinetic energy of electrons.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Safari, L., E-mail: laleh.safari@ist.ac.at; Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu; Santos, J. P.

Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.

Quantum Monte Carlo for electronic structure: Recent developments and applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriquez, Maria Milagos Soto

Quantum Monte Carlo (QMC) methods have been found to give excellent results when applied to chemical systems. The main goal of the present work is to use QMC to perform electronic structure calculations. In QMC, a Monte Carlo simulation is used to solve the Schroedinger equation, taking advantage of its analogy to a classical diffusion process with branching. In the present work the author focuses on how to extend the usefulness of QMC to more meaningful molecular systems. This study is aimed at questions concerning polyatomic and large atomic number systems. The accuracy of the solution obtained is determined bymore » the accuracy of the trial wave function`s nodal structure. Efforts in the group have given great emphasis to finding optimized wave functions for the QMC calculations. Little work had been done by systematically looking at a family of systems to see how the best wave functions evolve with system size. In this work the author presents a study of trial wave functions for C, CH, C 2H and C 2H 2. The goal is to study how to build wave functions for larger systems by accumulating knowledge from the wave functions of its fragments as well as gaining some knowledge on the usefulness of multi-reference wave functions. In a MC calculation of a heavy atom, for reasonable time steps most moves for core electrons are rejected. For this reason true equilibration is rarely achieved. A method proposed by Batrouni and Reynolds modifies the way the simulation is performed without altering the final steady-state solution. It introduces an acceleration matrix chosen so that all coordinates (i.e., of core and valence electrons) propagate at comparable speeds. A study of the results obtained using their proposed matrix suggests that it may not be the optimum choice. In this work the author has found that the desired mixing of coordinates between core and valence electrons is not achieved when using this matrix. A bibliography of 175 references is included.« less

Shock-wave structure in a partially ionized gas

NASA Technical Reports Server (NTRS)

Lu, C. S.; Huang, A. B.

1974-01-01

The structure of a steady plane shock in a partially ionized gas has been investigated using the Boltzmann equation with a kinetic model as the governing equation and the discrete ordinate method as a tool. The effects of the electric field induced by the charge separation on the shock structure have also been studied. Although the three species of an ionized gas travel with approximately the same macroscopic velocity, the individual distribution functions are found to be very different. In a strong shock the atom distribution function may have double peaks, while the ion distribution function has only one peak. Electrons are heated up much earlier than ions and atoms in a partially ionized gas. Because the interactions of electrons with atoms and with ions are different, the ion temperature can be different from the atom temperature.

Size Dependence of S-bonding on (111) Facets of Cu Nanoclusters

DOE PAGES

Boschen, Jeffery S.; Lee, Jiyoung; Windus, Theresa L.; ...

2016-04-21

We demonstrate a strong damped oscillatory size dependence of the adsorption energy for sulfur on the (111) facets of tetrahedral Cu nanoclusters up to sizes of ~300 atoms. This behavior reflects quantum size effects. Consistent results are obtained from density functional theory analyses utilizing either atomic orbital or plane-wave bases and using the same Perdew–Burke–Ernzerhof functional. Behavior is interpreted via molecular orbitals (MO), density of states (DOS), and crystal orbital Hamilton population (COHP) analyses.

Light scattering from an atomic gas under conditions of quantum degeneracy

NASA Astrophysics Data System (ADS)

Porozova, V. M.; Gerasimov, L. V.; Havey, M. D.; Kupriyanov, D. V.

2018-05-01

Elastic light scattering from a macroscopic atomic sample existing in the Bose-Einstein condensate phase reveals a unique physical configuration of interacting light and matter waves. However, the joint coherent dynamics of the optical excitation induced by an incident photon is influenced by the presence of incoherent scattering channels. For a sample of sufficient length the excitation transports as a polariton wave and the propagation Green's function obeys the scattering equation which we derive. The polariton dynamics could be tracked in the outgoing channel of the scattered photon as we show via numerical solution of the scattering equation for one-dimensional geometry. The results are analyzed and compared with predictions of the conventional macroscopic Maxwell theory for light scattering from a nondegenerate atomic sample of the same density and size.

Superconducting Qubit (transmon) coupled to Surface Acoustic Waves (SAWs)

NASA Astrophysics Data System (ADS)

Guo, Lingzhen; Johansson, Göran

We work on a hybrid system, which couples the transmon in circuit QED to the propagating mechanical modes of Surface Acoustic Waves (SAWs). This is an analogue of circuit QED system but replacing the microwave photons by SAW phonons. We investigate the quantum dynamics of a single transmon qubit coupled to surface acoustic waves (SAWs) via two distant connection points. Since the acoustic speed is five orders of magnitude slower than the speed of light, the travelling time between the two connection points needs to be taken into account. Therefore, we treat the transmon qubit as a giant atom with a deterministic time delay. We find that the spontaneous emission of the system, formed by the giant atom and the SAWs between its connection points, initially follows a polynomial decay law instead of an exponential one, as would be the case for a small atom. We obtain exact analytical results for the scattering properties of the giant atom up to two-phonon processes by using a diagrammatic approach. The time delay gives rise to novel features in the reflection, transmission, power spectra, and second-order correlation functions of the system. We show that the giant atom can generate entangled phonon pairs, which may have applications in quantum communication. L.G. acknowledges financial support from Carl-Zeiss Stiftung (0563-2.8/508/2).

Feasibility of antihydrogen atom containment in helium: a problem of electron-positron correlation investigated by the Monte Carol method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackman, T.M.

1987-01-01

A theoretical investigation of the interaction potential between the helium atom and the antihydrogen atom was performed for the purpose of determining the feasibility of antihydrogen atom containment. The interaction potential showed an energy barrier to collapse of this system. A variational estimate of the height of this energy barrier and estimates of lifetime with respect to electron-positron annihilation were determined by the Variational Monte Carlo method. This calculation allowed for an improvement over an SCF result through the inclusion of explicit correlation factors in the trial wave function. An estimate of the correlation energy of this system was determinedmore » by the Green's Function Monte Carlo (GFMC) method.« less

Theoretical derivation of laser-dressed atomic states by using a fractal space

NASA Astrophysics Data System (ADS)

Duchateau, Guillaume

2018-05-01

The derivation of approximate wave functions for an electron submitted to both a Coulomb and a time-dependent laser electric fields, the so-called Coulomb-Volkov (CV) state, is addressed. Despite its derivation for continuum states does not exhibit any particular problem within the framework of the standard theory of quantum mechanics (QM), difficulties arise when considering an initially bound atomic state. Indeed the natural way of translating the unperturbed momentum by the laser vector potential is no longer possible since a bound state does not exhibit a plane wave form explicitly including a momentum. The use of a fractal space permits to naturally define a momentum for a bound wave function. Within this framework, it is shown how the derivation of laser-dressed bound states can be performed. Based on a generalized eikonal approach, a new expression for the laser-dressed states is also derived, fully symmetric relative to the continuum or bound nature of the initial unperturbed wave function. It includes an additional crossed term in the Volkov phase which was not obtained within the standard theory of quantum mechanics. The derivations within this fractal framework have highlighted other possible ways to derive approximate laser-dressed states in QM. After comparing the various obtained wave functions, an application to the prediction of the ionization probability of hydrogen targets by attosecond XUV pulses within the sudden approximation is provided. This approach allows to make predictions in various regimes depending on the laser intensity, going from the non-resonant multiphoton absorption to tunneling and barrier-suppression ionization.

The "Fermi hole" and the correlation introduced by the symmetrization or the anti-symmetrization of the wave function.

PubMed

Giner, Emmanuel; Tenti, Lorenzo; Angeli, Celestino; Malrieu, Jean-Paul

2016-09-28

The impact of the antisymmetrization is often addressed as a local property of the many-electron wave function, namely that the wave function should vanish when two electrons with parallel spins are in the same position in space. In this paper, we emphasize that this presentation is unduly restrictive: we illustrate the strong non-local character of the antisymmetrization principle, together with the fact that it is a matter of spin symmetry rather than spin parallelism. To this aim, we focus our attention on the simplest representation of various states of two-electron systems, both in atomic (helium atom) and molecular (H 2 and the π system of the ethylene molecule) cases. We discuss the non-local property of the nodal structure of some two-electron wave functions, both using analytical derivations and graphical representations of cuttings of the nodal hypersurfaces. The attention is then focussed on the impact of the antisymmetrization on the maxima of the two-body density, and we show that it introduces strong correlation effects (radial and/or angular) with a non-local character. These correlation effects are analyzed in terms of inflation and depletion zones, which are easily identifiable, thanks to the nodes of the orbitals composing the wave function. Also, we show that the correlation effects induced by the antisymmetrization occur also for anti-parallel spins since all M s components of a given spin state have the same N-body densities. Finally, we illustrate that these correlation effects occur also for the singlet states, but they have strictly opposite impacts: the inflation zones in the triplet become depletion zones in the singlet and vice versa.

Matter-wave propagation in optical lattices: geometrical and flat-band effects

DOE PAGES

Metcalf, Mekena; Chern, Gia-Wei; Di Ventra, Massimiliano; ...

2016-03-17

Here we report that the geometry of optical lattices can be engineered allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question feasible to atomic systems is related to the speed of propagation of matter-waves as a function of the lattice geometry. To address this issue, we have investigated theoretically the quantum transport of non-interacting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, and the cross-linked square latticemore » has an even faster propagation velocity. The increase results from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity due to its localized atoms. Lastly, we discuss possible realizations of those dynamical phenomena.« less

Projector Augmented-Wave formulation of response to strain and electric field perturbation within the density-functional perturbation theory

NASA Astrophysics Data System (ADS)

Martin, Alexandre; Torrent, Marc; Caracas, Razvan

2015-03-01

A formulation of the response of a system to strain and electric field perturbations in the pseudopotential-based density functional perturbation theory (DFPT) has been proposed by D.R Hamman and co-workers. It uses an elegant formalism based on the expression of DFT total energy in reduced coordinates, the key quantity being the metric tensor and its first and second derivatives. We propose to extend this formulation to the Projector Augmented-Wave approach (PAW). In this context, we express the full elastic tensor including the clamped-atom tensor, the atomic-relaxation contributions (internal stresses) and the response to electric field change (piezoelectric tensor and effective charges). With this we are able to compute the elastic tensor for all materials (metals and insulators) within a fully analytical formulation. The comparison with finite differences calculations on simple systems shows an excellent agreement. This formalism has been implemented in the plane-wave based DFT ABINIT code. We apply it to the computation of elastic properties and seismic-wave velocities of iron with impurity elements. By analogy with the materials contained in meteorites, tested impurities are light elements (H, O, C, S, Si).

A Study of the Errors of the Fixed-Node Approximation in Diffusion Monte Carlo

NASA Astrophysics Data System (ADS)

Rasch, Kevin M.

Quantum Monte Carlo techniques stochastically evaluate integrals to solve the many-body Schrodinger equation. QMC algorithms scale favorably in the number of particles simulated and enjoy applicability to a wide range of quantum systems. Advances in the core algorithms of the method and their implementations paired with the steady development of computational assets have carried the applicability of QMC beyond analytically treatable systems, such as the Homogeneous Electron Gas, and have extended QMC's domain to treat atoms, molecules, and solids containing as many as several hundred electrons. FN-DMC projects out the ground state of a wave function subject to constraints imposed by our ansatz to the problem. The constraints imposed by the fixed-node Approximation are poorly understood. One key step in developing any scientific theory or method is to qualify where the theory is inaccurate and to quantify how erroneous it is under these circumstances. I investigate the fixed-node errors as they evolve over changing charge density, system size, and effective core potentials. I begin by studying a simple system for which the nodes of the trial wave function can be solved almost exactly. By comparing two trial wave functions, a single determinant wave function flawed in a known way and a nearly exact wave function, I show that the fixed-node error increases when the charge density is increased. Next, I investigate a sequence of Lithium systems increasing in size from a single atom, to small molecules, up to the bulk metal form. Over these systems, FN-DMC calculations consistently recover 95% or more of the correlation energy of the system. Given this accuracy, I make a prediction for the binding energy of Li4 molecule. Last, I turn to analyzing the fixed-node error in first and second row atoms and their molecules. With the appropriate pseudo-potentials, these systems are iso-electronic, show similar geometries and states. One would expect with identical number of particles involved in the calculation, errors in the respective total energies of the two iso-electronic species would be quite similar. I observe, instead, that the first row atoms and their molecules have errors larger by twice or more in size. I identify a cause for this difference in iso-electronic species. The fixed-node errors in all of these cases are calculated by careful comparison to experimental results, showing that FN-DMC to be a robust tool for understanding quantum systems and also a method for new investigations into the nature of many-body effects.

Absolute Definition of Phase Shift in the Elastic Scattering of a Particle from Compound Systems

NASA Technical Reports Server (NTRS)

Temkin, A.

1961-01-01

The projection of the target wave function on the total wave function of a scattered particle interacting with the target system is used to define an absolute phase shift including any multiples of pi. With this definition of the absolute phase shift, one can prove rigorously in the limit of zero energy for s-wave electrons scattered from atomic hydrogen that the triplet phase shift must approach a nonzero multiple of pi. One can further show that at least one pi of this phase shift is not connected with the existence of a bound state of the H- ion.

Platinum atomic wire encapsulated in gold nanotubes: A first principle study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nigam, Sandeep, E-mail: snigam@barc.gov.in; Majumder, Chiranjib; Sahoo, Suman K.

2014-04-24

The nanotubes of gold incorporated with platinum atomic wire have been investigated by means of firstprinciples density functional theory with plane wave pseudopotential approximation. The structure with zig-zag chain of Pt atoms in side gold is found to be 0.73 eV lower in energy in comparison to straight chain of platinum atoms. The Fermi level of the composite tube was consisting of d-orbitals of Pt atoms. Further interaction of oxygen with these tubes reveals that while tube with zig-zag Pt prefers dissociative adsorption of oxygen molecule, the gold tube with linear Pt wire favors molecular adsorption.

Monte Carlo wave-function description of losses in a one-dimensional Bose gas and cooling to the ground state by quantum feedback

NASA Astrophysics Data System (ADS)

Schemmer, M.; Johnson, A.; Photopoulos, R.; Bouchoule, I.

2017-04-01

The effect of atom losses on a homogeneous one-dimensional Bose gas lying within the quasicondensate regime is investigated using a Monte Carlo wave-function approach. The evolution of the system is calculated, conditioned by the loss sequence, namely, the times of individual losses and the position of the removed atoms. We describe the gas within the linearized Bogoliubov approach. For each mode, we find that, for a given quantum trajectory, the state of the system converges towards a coherent state, i.e., the ground state, displaced in phase space. We show that, provided losses are recorded with a temporal and spatially resolved detector, quantum feedback can be implemented and cooling to the ground state of one or several modes can be realized.

Energy levels and radiative rates for Ne-like ions from Cu to Ga

NASA Astrophysics Data System (ADS)

Singh, Narendra; Aggarwal, Sunny

2017-11-01

Energy levels, lifetimes and wave function compositions are computed for 127 fine structural levels in Ne-like ions (Z=29{-}31). Configuration interaction has been included among 51 configurations (generating 1016 levels) and multiconfigurational Dirac-Fock method is used to generate the wave functions. Similar calculations have also been performed using the fully relativistic flexible atomic code (FAC). Transition wavelength, oscillator strength, transition probabilities and line strength are reported for electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic quadrupole (M2) transitions from the ground level. We compared our calculated results with the available data in the literature. The calculated results are found to be in close agreement with the previous results. Further, we predict some new atomic data which may be important for plasma diagnostics.

Treatment of Ion-Atom Collisions Using a Partial-Wave Expansion of the Projectile Wavefunction

ERIC Educational Resources Information Center

Wong, T. G.; Foster, M.; Colgan, J.; Madison, D. H.

2009-01-01

We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge…

High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes.

PubMed

Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

2014-08-21

We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 10(4). When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 10(6).

High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes

PubMed Central

Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

2014-01-01

We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106. PMID:25142376

Evolution of ground-state wave function in CeCoIn5 upon Cd or Sn doping

NASA Astrophysics Data System (ADS)

Chen, K.; Strigari, F.; Sundermann, M.; Hu, Z.; Fisk, Z.; Bauer, E. D.; Rosa, P. F. S.; Sarrao, J. L.; Thompson, J. D.; Herrero-Martin, J.; Pellegrin, E.; Betto, D.; Kummer, K.; Tanaka, A.; Wirth, S.; Severing, A.

2018-01-01

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M4 ,5 edges of Cd- and Sn-doped CeCoIn5. The 4 f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In1-xCdx) 5 suggests that the 4 f -conduction-electron (c f ) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In1-ySny) 5 compresses the 4 f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4 f and conduction electrons, even conveying information about direction dependencies.

sp-d Exchange Interactions in Wave Function Engineered Colloidal CdSe/Mn:CdS Hetero-Nanoplatelets.

PubMed

Muckel, Franziska; Delikanli, Savas; Hernández-Martínez, Pedro Ludwig; Priesner, Tamara; Lorenz, Severin; Ackermann, Julia; Sharma, Manoj; Demir, Hilmi Volkan; Bacher, Gerd

2018-03-14

In two-dimensional (2D) colloidal semiconductor nanoplatelets, which are atomically flat nanocrystals, the precise control of thickness and composition on the atomic scale allows for the synthesis of heterostructures with well-defined electron and hole wave function distributions. Introducing transition metal dopants with a monolayer precision enables tailored magnetic exchange interactions between dopants and band states. Here, we use the absorption based technique of magnetic circular dichroism (MCD) to directly prove the exchange coupling of magnetic dopants with the band charge carriers in hetero-nanoplatelets with CdSe core and manganese-doped CdS shell (CdSe/Mn:CdS). We show that the strength of both the electron as well as the hole exchange interactions with the dopants can be tuned by varying the nanoplatelets architecture with monolayer accuracy. As MCD is highly sensitive for excitonic resonances, excited level spectroscopy allows us to resolve and identify, in combination with wave function calculations, several excited state transitions including spin-orbit split-off excitonic contributions. Thus, our study not only demonstrates the possibility to expand the extraordinary physical properties of colloidal nanoplatelets toward magneto-optical functionality by transition metal doping but also provides an insight into the excited state electronic structure in this novel two-dimensional material.

Molecular Properties by Quantum Monte Carlo: An Investigation on the Role of the Wave Function Ansatz and the Basis Set in the Water Molecule

PubMed Central

Zen, Andrea; Luo, Ye; Sorella, Sandro; Guidoni, Leonardo

2014-01-01

Quantum Monte Carlo methods are accurate and promising many body techniques for electronic structure calculations which, in the last years, are encountering a growing interest thanks to their favorable scaling with the system size and their efficient parallelization, particularly suited for the modern high performance computing facilities. The ansatz of the wave function and its variational flexibility are crucial points for both the accurate description of molecular properties and the capabilities of the method to tackle large systems. In this paper, we extensively analyze, using different variational ansatzes, several properties of the water molecule, namely, the total energy, the dipole and quadrupole momenta, the ionization and atomization energies, the equilibrium configuration, and the harmonic and fundamental frequencies of vibration. The investigation mainly focuses on variational Monte Carlo calculations, although several lattice regularized diffusion Monte Carlo calculations are also reported. Through a systematic study, we provide a useful guide to the choice of the wave function, the pseudopotential, and the basis set for QMC calculations. We also introduce a new method for the computation of forces with finite variance on open systems and a new strategy for the definition of the atomic orbitals involved in the Jastrow-Antisymmetrised Geminal power wave function, in order to drastically reduce the number of variational parameters. This scheme significantly improves the efficiency of QMC energy minimization in case of large basis sets. PMID:24526929

A combined electronegativity equalization and electrostatic potential fit method for the determination of atomic point charges.

PubMed

Berente, Imre; Czinki, Eszter; Náray-Szabó, Gábor

2007-09-01

We report an approach for the determination of atomic monopoles of macromolecular systems using connectivity and geometry parameters alone. The method is appropriate also for the calculation of charge distributions based on the quantum mechanically determined wave function and does not suffer from the mathematical instability of other electrostatic potential fit methods. Copyright 2007 Wiley Periodicals, Inc.

Resonance fluorescence based two- and three-dimensional atom localization

NASA Astrophysics Data System (ADS)

Wahab, Abdul; Rahmatullah; Qamar, Sajid

2016-06-01

Two- and three-dimensional atom localization in a two-level atom-field system via resonance fluorescence is suggested. For the two-dimensional localization, the atom interacts with two orthogonal standing-wave fields, whereas for the three-dimensional atom localization, the atom interacts with three orthogonal standing-wave fields. The effect of the detuning and phase shifts associated with the corresponding standing-wave fields is investigated. A precision enhancement in position measurement of the single atom can be noticed via the control of the detuning and phase shifts.

AuNx stabilization with interstitial nitrogen atoms: A Density Functional Theory Study

NASA Astrophysics Data System (ADS)

Quintero, J. H.; Gonzalez-Hernandez, R.; Ospina, R.; Mariño, A.

2017-06-01

Researchers have been studying 4d and 5d Series Transition Metal Nitrides lately as a result of the experimental production of AuN, PtN, CuN. In this paper, we used the Density Functional Theory (DFT) implementing a pseudopotential plane-wave method to study the incorporation of nitrogen atoms in the face-centered cube (fcc) lattice of gold (Au). First, we took the fcc structure of gold, and gradually located the nitrogen atoms in tetrahedral (TH) and octahedral (OH) interstitial sites. AuN stabilized in: 2OH (30%), 4OH and 4TH (50%), 4OH - 2TH (close to the wurtzite structure) and 6TH (60%). This leads us to think that AuN behaves like a Transition Metal Nitride since the nitrogen atoms look for tetrahedral sites.

Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function.

PubMed

Levashov, V A

2017-11-14

We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function

NASA Astrophysics Data System (ADS)

Levashov, V. A.

2017-11-01

We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

Visualization of atomic-scale phenomena in superconductors: application to FeSe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choubey, Peayush; Berlijn, Tom; Kreisel, Andreas

Here we propose a simple method of calculating inhomogeneous, atomic-scale phenomena in superconductors which makes use of the wave function information traditionally discarded in the construction of tight-binding models used in the Bogoliubov-de Gennes equations. The method uses symmetry- based first principles Wannier functions to visualize the effects of superconducting pairing on the distribution of electronic states over atoms within a crystal unit cell. Local symmetries lower than the global lattice symmetry can thus be exhibited as well, rendering theoretical comparisons with scanning tunneling spectroscopy data much more useful. As a simple example, we discuss the geometric dimer states observedmore » near defects in superconducting FeSe.« less

Visualization of atomic-scale phenomena in superconductors: application to FeSe

DOE PAGES

Choubey, Peayush; Berlijn, Tom; Kreisel, Andreas; ...

2014-10-31

Here we propose a simple method of calculating inhomogeneous, atomic-scale phenomena in superconductors which makes use of the wave function information traditionally discarded in the construction of tight-binding models used in the Bogoliubov-de Gennes equations. The method uses symmetry- based first principles Wannier functions to visualize the effects of superconducting pairing on the distribution of electronic states over atoms within a crystal unit cell. Local symmetries lower than the global lattice symmetry can thus be exhibited as well, rendering theoretical comparisons with scanning tunneling spectroscopy data much more useful. As a simple example, we discuss the geometric dimer states observedmore » near defects in superconducting FeSe.« less

Fundamental limitations of cavity-assisted atom interferometry

NASA Astrophysics Data System (ADS)

Dovale-Álvarez, M.; Brown, D. D.; Jones, A. W.; Mow-Lowry, C. M.; Miao, H.; Freise, A.

2017-11-01

Atom interferometers employing optical cavities to enhance the beam splitter pulses promise significant advances in science and technology, notably for future gravitational wave detectors. Long cavities, on the scale of hundreds of meters, have been proposed in experiments aiming to observe gravitational waves with frequencies below 1 Hz, where laser interferometers, such as LIGO, have poor sensitivity. Alternatively, short cavities have also been proposed for enhancing the sensitivity of more portable atom interferometers. We explore the fundamental limitations of two-mirror cavities for atomic beam splitting, and establish upper bounds on the temperature of the atomic ensemble as a function of cavity length and three design parameters: the cavity g factor, the bandwidth, and the optical suppression factor of the first and second order spatial modes. A lower bound to the cavity bandwidth is found which avoids elongation of the interaction time and maximizes power enhancement. An upper limit to cavity length is found for symmetric two-mirror cavities, restricting the practicality of long baseline detectors. For shorter cavities, an upper limit on the beam size was derived from the geometrical stability of the cavity. These findings aim to aid the design of current and future cavity-assisted atom interferometers.

Approximating the Helium Wavefunction in Positronium-Helium Scattering

NASA Technical Reports Server (NTRS)

DiRienzi, Joseph; Drachman, Richard J.

2003-01-01

In the Kohn variational treatment of the positronium- hydrogen scattering problem the scattering wave function is approximated by an expansion in some appropriate basis set, but the target and projectile wave functions are known exactly. In the positronium-helium case, however, a difficulty immediately arises in that the wave function of the helium target atom is not known exactly, and there are several ways to deal with the associated eigenvalue in formulating the variational scattering equations to be solved. In this work we will use the Kohn variational principle in the static exchange approximation to d e t e e the zero-energy scattering length for the Ps-He system, using a suite of approximate target functions. The results we obtain will be compared with each other and with corresponding values found by other approximation techniques.

Increasing circular synthetic aperture sonar resolution via adapted wave atoms deconvolution.

PubMed

Pailhas, Yan; Petillot, Yvan; Mulgrew, Bernard

2017-04-01

Circular Synthetic Aperture Sonar (CSAS) processing computes coherently Synthetic Aperture Sonar (SAS) data acquired along a circular trajectory. This approach has a number of advantages, in particular it maximises the aperture length of a SAS system, producing very high resolution sonar images. CSAS image reconstruction using back-projection algorithms, however, introduces a dissymmetry in the impulse response, as the imaged point moves away from the centre of the acquisition circle. This paper proposes a sampling scheme for the CSAS image reconstruction which allows every point, within the full field of view of the system, to be considered as the centre of a virtual CSAS acquisition scheme. As a direct consequence of using the proposed resampling scheme, the point spread function (PSF) is uniform for the full CSAS image. Closed form solutions for the CSAS PSF are derived analytically, both in the image and the Fourier domain. The thorough knowledge of the PSF leads naturally to the proposed adapted atom waves basis for CSAS image decomposition. The atom wave deconvolution is successfully applied to simulated data, increasing the image resolution by reducing the PSF energy leakage.

Extended wave-packet model to calculate energy-loss moments of protons in matter

NASA Astrophysics Data System (ADS)

Archubi, C. D.; Arista, N. R.

2017-12-01

In this work we introduce modifications to the wave-packet method proposed by Kaneko to calculate the energy-loss moments of a projectile traversing a target which is represented in terms of Gaussian functions for the momentum distributions of electrons in the atomic shells. These modifications are introduced using the Levine and Louie technique to take into account the energy gaps corresponding to the different atomic levels of the target. We use the extended wave-packet model to evaluate the stopping power, the energy straggling, the inverse mean free path, and the ionization cross sections for protons in several targets, obtaining good agreements for all these quantities on an extensive energy range that covers low-, intermediate-, and high-energy regions. The extended wave-packet model proposed here provides a method to calculate in a very straightforward way all the significant terms of the inelastic interaction of light ions with any element of the periodic table.

Model studies of hydrogen atom addition and abstraction processes involving ortho-, meta-, and para-benzynes.

PubMed

Clark, A E; Davidson, E R

2001-10-31

H-atom addition and abstraction processes involving ortho-, meta-, and para-benzyne have been investigated by multiconfigurational self-consistent field methods. The H(A) + H(B)...H(C) reaction (where r(BC) is adjusted to mimic the appropriate singlet-triplet energy gap) is shown to effectively model H-atom addition to benzyne. The doublet multiconfiguration wave functions are shown to mix the "singlet" and "triplet" valence bond structures of H(B)...H(C) along the reaction coordinate; however, the extent of mixing is dependent on the singlet-triplet energy gap (DeltaE(ST)) of the H(B)...H(C) diradical. Early in the reaction, the ground-state wave function is essentially the "singlet" VB function, yet it gains significant "triplet" VB character along the reaction coordinate that allows H(A)-H(B) bond formation. Conversely, the wave function of the first excited state is predominantly the "triplet" VB configuration early in the reaction coordinate, but gains "singlet" VB character when the H-atom is close to a radical center. As a result, the potential energy surface (PES) for H-atom addition to triplet H(B)...H(C) diradical is repulsive! The H3 model predicts, in agreement with the actual calculations on benzyne, that the singlet diradical electrons are not coupled strongly enough to give rise to an activation barrier associated with C-H bond formation. Moreover, this model predicts that the PES for H-atom addition to triplet benzyne will be characterized by a repulsive curve early in the reaction coordinate, followed by a potential avoided crossing with the (pi)1(sigma*)1 state of the phenyl radical. In contrast to H-atom addition, large activation barriers characterize the abstraction process in both the singlet ground state and first triplet state. In the ground state, this barrier results from the weakly avoided crossing of the dominant VB configurations in the ground-state singlet (S0) and first excited singlet (S1) because of the large energy gap between S0 and S1 early in the reaction coordinate. Because the S1 state is best described as the combination of the triplet X-H bond and the triplet H(B)...H(C) spin couplings, the activation barrier along the S0 abstraction PES will have much less dependence on the DeltaE(ST) of H(B)...H(C) than previously speculated. For similar reasons, the T1 potential surface is quite comparable to the S0 PES.

First measurements of the index of refraction of gases for lithium atomic waves.

PubMed

Jacquey, M; Büchner, M; Trénec, G; Vigué, J

2007-06-15

We report the first measurements of the index of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary parts of the index of refraction n for argon, krypton, and xenon as a function of the gas density for several velocities of the lithium beam. The linear dependence of (n-1) with the gas density is well verified. The total collision cross section deduced from the imaginary part of (n-1) is in very good agreement with traditional measurements of this quantity. Finally, the real and imaginary parts of (n-1) and their ratio rho exhibit glory oscillations, in good agreement with calculations.

Plasma-screening effects on the electron-impact excitation of hydrogenic ions in dense plasmas

NASA Technical Reports Server (NTRS)

Jung, Young-Dae

1993-01-01

Plasma-screening effects are investigated on electron-impact excitation of hydrogenic ions in dense plasmas. Scaled cross sections Z(exp 4) sigma for 1s yields 2s and 1s yields 2p are obtained for a Debye-Hueckel model of the screened Coulomb interaction. Ground and excited bound wave functions are modified in the screened Coulomb potential (Debye-Hueckel model) using the Ritz variation method. The resulting atomic wave functions and their eigenenergies agree well with the numerical and high-order perturbation theory calculations for the interesting domain of the Debye length not less than 10. The Born approximation is used to describe the continuum states of the projectile electron. Plasma screening effects on the atomic electrons cannot be neglected in the high-density cases. Including these effects, the cross sections are appreciably increased for 1s yields 2s transitions and decreased for 1s yields 2p transitions.

ELECTRONIC STRUCTURE FOR THE GROUND STATE OF T1H FROM RELATIVISTIC MULTICONFIGURATION SCF CALCULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christiansen, P.A.; Pitzer, K.S.

The dissociation curve for the ground state of TlH was computed using a relativistic {omega}-{omega} coupling formalism. The relativistic effects represented by the Dirac equation were introduced using effective potentials generated from atomic Dirac-Fock wave functions using a generalization of the improved effective potential formulation of Christiansen, Lee, and Pitzer. The multiconfiguration SCF treatment used is a generalization of the two-component molecular spinor formalism of Lee, Ermler, and Pitzer. Using a five configuration wave function we were able to obtain approximately 85% of the experimental dissociation energy. Our computations indicate that the bond is principally sigma in form, despite themore » large spin-orbit splitting in atomic thallium. Furthermore the bond appears to be slightly ionic (Tl{sup +}H{sup -}) with about 0.3 extra electron charge on the hydrogen.« less

Electronic structure for the ground state of TlH from relativistic multiconfiguration SCF calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christiansen, P.A.; Pitzer, K.S.

The dissociation curve for the ground state of TlH was computed using a relativistic ..omega..--..omega.. coupling formalism. The relativistic effects represented by the Dirac equation were introduced using effective potentials generated from atomic Dirac--Fock wave functions using a generalization of the improved effective potential formulation of Christiansen, Lee, and Pitzer. The multiconfiguration SCF treatment used is a generalization of the two-component molecular spinor formalism of Lee, Ermler, and Pitzer. Using a five configuration wave function we were able to obtain approximately 85% of the experimental dissociation energy. Our computations indicate that the bond is principally sigma in form, despite themore » large spin--orbit splitting in atomic thallium. Furthermore the bond appears to be slightly ionic (Tl/sup +/H/sup -/) with about 0.3 extra electron charge on the hydrogen.« less

Momentum-resolved radio-frequency spectroscopy of a spin-orbit-coupled atomic Fermi gas near a Feshbach resonance in harmonic traps

NASA Astrophysics Data System (ADS)

Peng, Shi-Guo; Liu, Xia-Ji; Hu, Hui; Jiang, Kaijun

2012-12-01

We theoretically investigate the momentum-resolved radio-frequency spectroscopy of a harmonically trapped atomic Fermi gas near a Feshbach resonance in the presence of equal Rashba and Dresselhaus spin-orbit coupling. The system is qualitatively modeled as an ideal gas mixture of atoms and molecules, in which the properties of molecules, such as the wave function, binding energy, and effective mass, are determined from the two-particle solution of two interacting atoms. We calculate separately the radio-frequency response from atoms and molecules at finite temperatures by using the standard Fermi golden rule and take into account the effect of harmonic traps within local density approximation. The total radio-frequency spectroscopy is discussed as functions of temperature and spin-orbit coupling strength. Our results give a qualitative picture of radio-frequency spectroscopy of a resonantly interacting spin-orbit-coupled Fermi gas and can be directly tested in atomic Fermi gases of 40K atoms at Shanxi University and 6Li atoms at the Massachusetts Institute of Technology.

Static electric dipole polarizability of lithium atoms in Debye plasmas

NASA Astrophysics Data System (ADS)

Ning, Li-Na; Qi, Yue-Ying

2012-12-01

The static electric dipole polarizabilities of the ground state and n <= 3 excited states of a lithium atom embedded in a weekly coupled plasma environment are investigated as a function of the plasma screening radium. The plasma screening of the Coulomb interaction is described by the Debye—Hückel potential and the interaction between the valence electron and the atomic core is described by a model potential. The electron energies and wave functions for both the bound and continuum states are calculated by solving the Schrödinger equation numerically using the symplectic integrator. The oscillator strengths, partial-wave, and total static dipole polarizabilities of the ground state and n <= 3 excited states of the lithium atom are calculated. Comparison of present results with those of other authors, when available, is made. The results for the 2s ground state demonstrated that the oscillator strengths and the static dipole polarizabilities from np orbitals do not always increase or decrease with the plasma screening effect increasing, unlike that for hydrogen-like ions, especially for 2s→3p transition there is a zero value for both the oscillator strength and the static dipole polarizability for screening length D = 10.3106a0, which is associated with the Cooper minima.

Electronic wave function and binding effects in M-shell ionization of gold by protons

NASA Astrophysics Data System (ADS)

Pajek, M.; Banaś, D.; Jabłoński, Ł.; Mukoyama, T.

2018-02-01

The measured M-X-ray production cross sections for protons, which are used in the particle induced X-ray emission (PIXE) technique, are systematically underestimated for low impact energies by the ECPSSR and ECUSAR theories. These theories, which are based on the plane wave Born approximation (PWBA) and use the screened hydrogenic wave functions, include corrections for the projectile Coulomb deflection and electron relativistic and binding effects. In the present paper, in order to interpret the observed disagreement at low impact energies, the systematic calculations of the M-shell ionization cross sections for gold were performed using the semiclassical (SCA) and the binary encounter (BEA) approximations in order to identify a role of the electronic wave function and electron binding effects. In these calculations the different wave functions, from nonrelativistic hydrogenic to selfconsistent Dirac-Hartree-Fock, were considered and the binding effect was treated within extreme separated- (SA) and united-atoms (UA) limits. The results are discussed in details and the observed discrepancies are attributed to inadequate description of the electron binding effect at the lowest impact energies for which the molecular approach is required.

Hydrogen atom abstraction from aldehydes - OH + H2CO and O + H2CO

NASA Technical Reports Server (NTRS)

Dupuis, M.; Lester, W. A., Jr.

1984-01-01

The essential features of the potential energy surfaces governing hydrogen abstraction from formaldehyde by oxygen atom and hydroxyl radical have been characterized with ab inito multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) wave functions. The results are consistent with a very small activation energy for the OH + H2CO reaction, and an activation energy of a few kcal/mol for the O + H2CO reaction. In the transition state structure of both systems, the attacking oxygen atom is nearly collinear with the attacked CH bond.

Atom Interferometry for Detection of Gravitational Waves: Progress and Prospects

NASA Astrophysics Data System (ADS)

Hogan, Jason

2015-04-01

Gravitational wave astronomy promises to provide a new window into the universe, collecting information about astrophysical systems and cosmology that is difficult or impossible to acquire by other methods. Detector designs based on atom interferometry offer a number of advantages over traditional approaches, including access to conventionally inaccessible frequency ranges and substantially reduced antenna baselines. Atomic physics techniques also make it possible to build a gravitational wave detector with a single linear baseline, potentially offering advantages in cost and design flexibility. In support of these proposals, recent progress in long baseline atom interferometry has enabled observation of matter wave interference with atomic wavepacket separations exceeding 10 cm and interferometer durations of more than 2 seconds. These results are obtained in a 10-meter drop tower incorporating large momentum transfer atom optics. This approach can provide ground-based proof-of-concept demonstrations of many of the technical requirements of both terrestrial and satellite gravitational wave detectors.

Nodal surfaces and interdimensional degeneracies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loos, Pierre-François, E-mail: pf.loos@anu.edu.au; Bressanini, Dario, E-mail: dario.bressanini@uninsubria.it

2015-06-07

The aim of this paper is to shed light on the topology and properties of the nodes (i.e., the zeros of the wave function) in electronic systems. Using the “electrons on a sphere” model, we study the nodes of two-, three-, and four-electron systems in various ferromagnetic configurations (sp, p{sup 2}, sd, pd, p{sup 3}, sp{sup 2}, and sp{sup 3}). In some particular cases (sp, p{sup 2}, sd, pd, and p{sup 3}), we rigorously prove that the non-interacting wave function has the same nodes as the exact (yet unknown) wave function. The number of atomic and molecular systems for whichmore » the exact nodes are known analytically is very limited and we show here that this peculiar feature can be attributed to interdimensional degeneracies. Although we have not been able to prove it rigorously, we conjecture that the nodes of the non-interacting wave function for the sp{sup 3} configuration are exact.« less

Two-body Schrödinger wave functions in a plane-wave basis via separation of dimensions

NASA Astrophysics Data System (ADS)

Jerke, Jonathan; Poirier, Bill

2018-03-01

Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy—i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted—as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.

Two-body Schrödinger wave functions in a plane-wave basis via separation of dimensions.

PubMed

Jerke, Jonathan; Poirier, Bill

2018-03-14

Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy-i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted-as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.

Coherent wave packet dynamics in a double-well potential in cavity

NASA Astrophysics Data System (ADS)

Zheng, Li; Li, Gang; Ding, Ming-Song; Wang, Yong-Liang; Zhang, Yun-Cui

2018-02-01

We investigate the coherent wave packet dynamics of a two-level atom trapped in a symmetric double-well potential in a near-resonance cavity. Prepared on one side of the double-well potential, the atom wave packet oscillates between the left and right wells, while recoil induced by the emitted photon from the atom entangles the atomic internal and external degrees of freedom. The collapse and revival of the tunneling occurs. Adjusting the width of the wave packets, one can modify the tunneling frequency and suppress the tunneling.

Dynamic non-reciprocal meta-surfaces with arbitrary phase reconfigurability based on photonic transition in meta-atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Yu; Fan, Shanhui, E-mail: shanhui@stanford.edu

2016-01-11

We introduce a distinct class of dynamic non-reciprocal meta-surfaces with arbitrary phase-reconfigurability. This meta-surface consists of an array of meta-atoms, each of which is subject to temporal refractive index modulation, which induces photonic transitions between the states of the meta-atom. We show that arbitrary phase profile for the outgoing wave can be achieved by controlling the phase of the modulation at each meta-atom. Moreover, such dynamic meta-surfaces exhibit non-reciprocal response without the need for magneto-optical effects. The use of photonic transition significantly enhances the tunability and the possible functionalities of meta-surfaces.

Orbital dependent functionals: An atom projector augmented wave method implementation

NASA Astrophysics Data System (ADS)

Xu, Xiao

This thesis explores the formulation and numerical implementation of orbital dependent exchange-correlation functionals within electronic structure calculations. These orbital-dependent exchange-correlation functionals have recently received renewed attention as a means to improve the physical representation of electron interactions within electronic structure calculations. In particular, electron self-interaction terms can be avoided. In this thesis, an orbital-dependent functional is considered in the context of Hartree-Fock (HF) theory as well as the Optimized Effective Potential (OEP) method and the approximate OEP method developed by Krieger, Li, and Iafrate, known as the KLI approximation. In this thesis, the Fock exchange term is used as a simple well-defined example of an orbital-dependent functional. The Projected Augmented Wave (PAW) method developed by P. E. Blochl has proven to be accurate and efficient for electronic structure calculations for local and semi-local functions because of its accurate evaluation of interaction integrals by controlling multiple moments. We have extended the PAW method to treat orbital-dependent functionals in Hartree-Fock theory and the Optimized Effective Potential method, particularly in the KLI approximation. In the course of study we develop a frozen-core orbital approximation that accurately treats the core electron contributions for above three methods. The main part of the thesis focuses on the treatment of spherical atoms. We have investigated the behavior of PAW-Hartree Fock and PAW-KLI basis, projector, and pseudopotential functions for several elements throughout the periodic table. We have also extended the formalism to the treatment of solids in a plane wave basis and implemented PWPAW-KLI code, which will appear in future publications.

Angular-momentum couplings in ultra-long-range giant dipole molecules

NASA Astrophysics Data System (ADS)

Stielow, Thomas; Scheel, Stefan; Kurz, Markus

2018-02-01

In this article we extend the theory of ultra-long-range giant dipole molecules, formed by an atom in a giant dipole state and a ground-state alkali-metal atom, by angular-momentum couplings known from recent works on Rydberg molecules. In addition to s -wave scattering, the next higher order of p -wave scattering in the Fermi pseudopotential describing the binding mechanism is considered. Furthermore, the singlet and triplet channels of the scattering interaction as well as angular-momentum couplings such as hyperfine interaction and Zeeman interactions are included. Within the framework of Born-Oppenheimer theory, potential energy surfaces are calculated in both first-order perturbation theory and exact diagonalization. Besides the known pure triplet states, mixed-spin character states are obtained, opening up a whole new landscape of molecular potentials. We determine exact binding energies and wave functions of the nuclear rotational and vibrational motion numerically from the various potential energy surfaces.

Localizing high-lying Rydberg wave packets with two-color laser fields

NASA Astrophysics Data System (ADS)

Larimian, Seyedreza; Lemell, Christoph; Stummer, Vinzenz; Geng, Ji-Wei; Roither, Stefan; Kartashov, Daniil; Zhang, Li; Wang, Mu-Xue; Gong, Qihuang; Peng, Liang-You; Yoshida, Shuhei; Burgdörfer, Joachim; Baltuška, Andrius; Kitzler, Markus; Xie, Xinhua

2017-08-01

We demonstrate control over the localization of high-lying Rydberg wave packets in argon atoms with phase-locked orthogonally polarized two-color laser fields. With a reaction microscope, we measure ionization signals of high-lying Rydberg states induced by a weak dc field and blackbody radiation as a function of the relative phase between the two-color fields. We find that the dc-field-ionization yield of high-lying Rydberg argon atoms oscillates with the relative two-color phase with a period of 2 π while the photoionization signal by blackbody radiation shows a period of π . Accompanying simulations show that these observations are a clear signature of the asymmetric localization of electrons recaptured into very elongated (low angular momentum) high-lying Rydberg states after conclusion of the laser pulse. Our findings thus open an effective pathway to control the localization of high-lying Rydberg wave packets.

Calculated gadolinium atomic electron energy levels and Auger electron emission probability as a function of atomic number Z

NASA Astrophysics Data System (ADS)

Miloshevsky, G. V.; Tolkach, V. I.; Shani, Gad; Rozin, Semion

2002-06-01

Auger electron interaction with matter is gaining importance in particular in medical application of radiation. The production probability and energy spectrum is therefore of great importance. A good source of Auger electrons is the 157Gd(n,γ) 158Gd reaction. The present article describes calculations of electron levels in Gd atoms and provides missing data of outer electron energy levels. The energy of these electron levels missing in published tables, was found to be in the 23-24 and 6-7 eV energy ranges respectively. The probability of Auger emission was calculated as an interaction of wave function of the initial and final electron states. The wave functions were calculated using the Hartree-Fock-Slater approximation with relativistic correction. The equations were solved using a spherical symmetry potential. The error for inner shell level is less than 10%, it is increased to the order of 10-15% for the outer shells. The width of the Auger process changes from 0.1 to 1.2 eV for atomic number Z from 5 to 70. The fluorescence yield width changes five orders of magnitude in this range. Auger electron emission width from the K shell changes from 10 -2 to ˜1 eV with Z changing from 10 to 64, depending on the final state. For the L shell it changes from 0 to 0.25 when it Z changes from 20 to 64.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trubilko, A. I., E-mail: trubilko.andrey@gmail.com

Coherent scattering of a two-level atom in the field of a quantized standing wave of a micromaser is considered under conditions of initial quantum correlation between the atom and the field. Such a correlation can be produced by a broadband parametric source. The interaction leading to scattering of the atom from the nonuniform field occurs in the dispersion limit or in the wing of the absorption line of the atom. Apart from the quantized field, the atom simultaneously interacts with two classical counterpropagating waves with different frequencies, which are acting in the plane perpendicular to the atom’s propagation velocity andmore » to the wavevector of the standing wave. Joint action of the quantized field and two classical waves induces effective two-photon and Raman resonance interaction on the working transition. The effective Hamiltonian of the interaction is derived using the unitary transformation method developed for a moving atom. A strong effect is detected, which makes it possible to distinguish the correlated initial state of the atom and the field in the scattering of atom from the state of independent systems. For all three waves, scattering is not observed when systems with quantum correlation are prepared using a high-intensity parametric source. Conversely, when the atom interacts only with the nonuniform field of the standing wave, scattering is not observed in the case of the initial factorized state.« less

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

DOE PAGES

Chen, K.; Strigari, F.; Sundermann, M.; ...

2018-01-17

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, K.; Strigari, F.; Sundermann, M.

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Distinguishing between evidence and its explanations in the steering of atomic clocks

NASA Astrophysics Data System (ADS)

Myers, John M.; Hadi Madjid, F.

2014-11-01

Quantum theory reflects within itself a separation of evidence from explanations. This separation leads to a known proof that: (1) no wave function can be determined uniquely by evidence, and (2) any chosen wave function requires a guess reaching beyond logic to things unforeseeable. Chosen wave functions are encoded into computer-mediated feedback essential to atomic clocks, including clocks that step computers through their phases of computation and clocks in space vehicles that supply evidence of signal propagation explained by hypotheses of spacetimes with metric tensor fields. The propagation of logical symbols from one computer to another requires a shared rhythm-like a bucket brigade. Here we show how hypothesized metric tensors, dependent on guesswork, take part in the logical synchronization by which clocks are steered in rate and position toward aiming points that satisfy phase constraints, thereby linking the physics of signal propagation with the sharing of logical symbols among computers. Recognizing the dependence of the phasing of symbol arrivals on guesses about signal propagation transports logical synchronization from the engineering of digital communications to a discipline essential to physics. Within this discipline we begin to explore questions invisible under any concept of time that fails to acknowledge unforeseeable events. In particular, variation of spacetime curvature is shown to limit the bit rate of logical communication.

Orbital electron capture by the nucleus

NASA Technical Reports Server (NTRS)

Bambynek, W.; Behrens, H.; Chen, M. H.; Crasemann, B.; Fitzpatrick, M. L.; Ledingham, K. W. D.; Genz, H.; Mutterer, M.; Intemann, R. L.

1976-01-01

The theory of nuclear electron capture is reviewed in the light of current understanding of weak interactions. Experimental methods and results regarding capture probabilities, capture ratios, and EC/Beta(+) ratios are summarized. Radiative electron capture is discussed, including both theory and experiment. Atomic wave function overlap and electron exchange effects are covered, as are atomic transitions that accompany nuclear electron capture. Tables are provided to assist the reader in determining quantities of interest for specific cases.

Angular distribution of photoelectrons from atomic oxygen, nitrogen and carbon. [in upper atmosphere

NASA Technical Reports Server (NTRS)

Manson, S. J.; Kennedy, D. J.; Starace, A. F.; Dill, D.

1974-01-01

The angular distributions of photoelectrons from atomic oxygen, nitrogen, and carbon are calculated. Both Hartree-Fock and Hartree-Slater (Herman-Skillman) wave functions are used for oxygen, and the agreement is excellent; thus only Hartree-Slater functions are used for carbon and nitrogen. The pitch-angle distribution of photoelectrons is discussed, and it is shown that previous approximations of energy-independent isotropic or sin squared theta distributions are at odds with the authors' results, which vary with energy. This variation with energy is discussed, as is the reliability of these calculations.

Tables Of Gaussian-Type Orbital Basis Functions

NASA Technical Reports Server (NTRS)

Partridge, Harry

1992-01-01

NASA technical memorandum contains tables of estimated Hartree-Fock wave functions for atoms lithium through neon and potassium through krypton. Sets contain optimized Gaussian-type orbital exponents and coefficients, and near Hartree-Fock quality. Orbital exponents optimized by minimizing restricted Hartree-Fock energy via scaled Newton-Raphson scheme in which Hessian evaluated numerically by use of analytically determined gradients.

2016 Summer Series - Mark Kasevich: Quantum Mechanics at Macroscopic Scales

NASA Image and Video Library

2016-06-09

The underpinning of the universe is quantum mechanics. It can be used to explain the observed particle and wave nature of atoms. Atom interferometry uses the wave characteristics of atoms to investigate fundamental physics and advance our understanding of the macroscopic world. NASA is working with Dr. Mark Kasevich to apply this technology to advance astrophysics and improve navigation. In his seminar, Kasevich will delve into the world of atom interferometry, gravitational waves and quantum sensors.

Non-expanded dispersion and induction energies, and damping functions, for molecular interactions with application to HF-He

NASA Astrophysics Data System (ADS)

Knowles, Peter J.; Meath, William J.

The evaluation of second order non-expanded dispersion and induction energies, and the associated damping functions, for interactions involving molecules is discussed with emphasis placed on using the time-dependent coupled Hartree-Fock method. Results are given for the HF-He interaction for all individual partial wave non-expanded dispersion and induction energies varying asymptotically for large R through O(R-8) and O(R-10) respectively and for most of the individual dispersion energies varying as R-9 and R-10. They are used to illustrate various features of charge overlap effects and the damping functions for molecular interactions, which are considerably more complicated than for atom-atom interactions.

Techniques for measuring the atomic recoil frequency using a grating-echo atom interferometer

NASA Astrophysics Data System (ADS)

Barrett, Brynle

I have developed three types of time-domain echo atom interferometer (AIs) that use either two or three standing-wave pulses in different configurations. Experiments approaching the transit time limit are achieved using samples of laser-cooled rubidium atoms with temperatures < 5 μK contained within a glass vacuum chamber—an environment that is largely free of both magnetic fields and field gradients. The principles of the atom-interferometric measurement of Eq can be understood based on a description of the "two-pulse" AI. This interferometer uses two standing-wave pulses applied at times t = 0 and t = T 21 to create a superposition of atomic momentum states differing by multiples of the two-photon momentum, ħq = 2 ħk where k is the optical wave number, that interfere in the vicinity of t = 2T 21. This interference or "echo" manifests itself as a density grating in the atomic sample, and is probed by applying a near-resonant traveling-wave "read-out" pulse and measuring the intensity of the coherent light Bragg-scattered in the backward direction. The scattered light from the grating is associated with a λ/2-periodic modulation produced by the interference of momentum states differing by ħq. Interfering states that differ by more than ħq—which produce higher-frequency spatial modulation within the sample—cannot be detected due to the nature of the Bragg scattering detection technique employed in the experiment. The intensity of the scattered light varies in a periodic manner as a function of the standing-wave pulse separation, T21. The fundamental frequency of this modulation is the two-photon atomic recoil frequency, ω q = ħq2/2M, where q = 2k and M is the mass of the atom (a rubidium isotope in this case). The recoil frequency, ω q, is related to the recoil energy, Eq = ħωq, which is the kinetic energy associated with the recoil of the atom after a coherent two-photon scattering process. By performing the experiment on a suitably long time scale ( T21 >> τq = π/ω q ˜32 μs), ωq can be measured precisely. Since ωq contains the ratio of Planck's constant to the mass of the atom, h/M, a precise measurement of ωq can be used as a strict test of quantum theories of the electromagnetic force. This two-pulse technique has a number of disadvantages for a precision measurement of ωq, such as a complicated functional dependence on T21 (due to the nature of Kapitza-Dirac diffraction, the level structure of the atom, and spontaneous emission). However, many of these difficulties can be avoided by using a three-pulse "perturbative" echo technique, where a third standing-wave pulse is applied at t = T21 + δT , with δT < T21. The function of the third pulse is to convert the difference between interfering momentum states from nħq (n > 1) to ħq. In this manner, interference between high-order momentum states contributes more significantly to the three-pulse echo than to the two-pulse echo. By fixing T21 and varying δT between the second standing-wave pulse and the echo time, the signal exhibits a simple shape with narrow fringes that revive periodically at the recoil period, τq. Using this technique, I have achieved a single measurement of ωq with a relative statistical uncertainty of ˜ 180 parts per 109 (ppb) on a time scale of 2T21 ˜ 72 ms in ˜ 15 minutes of data acquisition. Further improvements are anticipated by extending the experimental time scale and narrowing the signal fringe width. To demonstrate the final statistical uncertainty using the current configuration of the experiment, I acquired 82 individual measurements of ω q under the same experimental conditions. This resulted in a final measurement with a statistical precision of 37 ppb. However, this measurement is currently overwhelmed by systematic errors at the level of ˜ 5.7 parts per 106 (ppm). The first survey of systematic effects on the measurement of ωq with this technique has also been carried out, where individual measurements had relative statistical uncertainties of ≲ 1 ppm. These experimental studies, along with theoretical calculations, can be used to reduce and eliminate such effects in future rounds of experimentation. (Abstract shortened by UMI.).

Estimation of chirp rates of music-adapted prolate spheroidal atoms using reassignment

NASA Astrophysics Data System (ADS)

Mesz, Bruno; Serrano, Eduardo

2007-09-01

We introduce a modified Matching Pursuit algorithm for estimating frequency and frequency slope of FM-modulated music signals. The use of Matching Pursuit with constant frequency atoms provides coarse estimates which could be improved with chirped atoms, more suited in principle to this kind of signals. Application of the reassignment method is suggested by its good localization properties for chirps. We start considering a family of atoms generated by modulation and scaling of a prolate spheroidal wave function. These functions are concentrated in frequency on intervals of a semitone centered at the frequencies of the well-tempered scale. At each stage of the pursuit, we search the atom most correlated with the signal. We then consider the spectral peaks at each frame of the spectrogram and calculate a modified frequency and frequency slope using the derivatives of the reassignment operators; this is then used to estimate the parameters of a cubic interpolation polynomial that models local pitch fluctuations. We apply the method both to synthetic and music signals.

Atomic-level imaging, processing and characterization of semiconductor surfaces

DOEpatents

Kazmerski, Lawrence L.

1995-01-01

A method for selecting and removing single specific atoms from a solid material surface uses photon biasing to break down bonds that hold the selected atom in the lattice and to reduce barrier effects that hold the atom from transferring to a probe. The photon bias is preferably light or other electromagnetic radiation with a wavelength and frequency that approximately matches the wave function of the target atom species to be removed to induce high energy, selective thermionic-like vibration. An electric field potential is then applied between the probe and the surface of the solid material to pull the atom out of the lattice and to transfer the atom to the probe. Different extrinsic atoms can be installed in the lattice sites that are vacated by the removed atoms by using a photon bias that resonates the extrinsic atom species, reversing polarity of the electric field, and blowing gas comprising the extrinsic atoms through a hollow catheter probe.

Atomic-level imaging, processing and characterization of semiconductor surfaces

DOEpatents

Kazmerski, L.L.

1995-08-22

A method for selecting and removing single specific atoms from a solid material surface uses photon biasing to break down bonds that hold the selected atom in the lattice and to reduce barrier effects that hold the atom from transferring to a probe. The photon bias is preferably light or other electromagnetic radiation with a wavelength and frequency that approximately matches the wave function of the target atom species to be removed to induce high energy, selective thermionic-like vibration. An electric field potential is then applied between the probe and the surface of the solid material to pull the atom out of the lattice and to transfer the atom to the probe. Different extrinsic atoms can be installed in the lattice sites that are vacated by the removed atoms by using a photon bias that resonates the extrinsic atom species, reversing polarity of the electric field, and blowing gas comprising the extrinsic atoms through a hollow catheter probe. 8 figs.

Quantum delayed-choice experiment with a single neutral atom.

PubMed

Li, Gang; Zhang, Pengfei; Zhang, Tiancai

2017-10-01

We present a proposal to implement a quantum delayed-choice (QDC) experiment with a single neutral atom, such as a rubidium or cesium atom. In our proposal, a Ramsey interferometer is adopted to observe the wave-like or particle-like behaviors of a single atom depending on the existence or absence of the second π/2-rotation. A quantum-controlled π/2-rotation on target atom is realized through a Rydberg-Rydberg interaction by another ancilla atom. It shows that a heavy neutral atom can also have a morphing behavior between the particle and the wave. The realization of the QDC experiment with such heavy neutral atoms not only is significant to understand the Bohr's complementarity principle in matter-wave and matter-particle domains but also has great potential on the quantum information process with neutral atoms.

Experiments with BECs in a Painted Potential: Atom SQUID, Matter Wave Bessel Beams, and Matter Wave Circuits

NASA Astrophysics Data System (ADS)

Boshier, Malcolm; Ryu, Changhyun; Blackburn, Paul; Blinova, Alina; Henderson, Kevin

2014-05-01

The painted potential is a time-averaged optical dipole potential which is able to create arbitrary and dynamic two dimensional potentials for Bose Einstein condensates (BECs). This poster reports three recent experiments using this technique. First, we have realized the dc atom SQUID geometry of a BEC in a toroidal trap with two Josephson junctions. We observe Josephson effects, measure the critical current of the junctions, and find dynamic behavior that is in good agreement with the simple Josephson equations for a tunnel junction with the ideal sinusoidal current-phase relation expected for the parameters of the experiment. Second, we have used free expansion of a rotating toroidal BEC to create matter wave Bessel beams, which are of interest because perfect Bessel beams (plane waves with amplitude profiles described by Bessel functions) propagate without diffraction. Third, we have realized the basic circuit elements necessary to create complex matter wave circuits. We launch BECs at arbitrary velocity along straight waveguides, propagate them around curved waveguides and stadium-shaped waveguide traps, and split them coherently at y-junctions that can also act as switches. Supported by LANL/LDRD.

Optical atomic phase reference and timing.

PubMed

Hollberg, L; Cornell, E H; Abdelrahmann, A

2017-08-06

Atomic clocks based on laser-cooled atoms have made tremendous advances in both accuracy and stability. However, advanced clocks have not found their way into widespread use because there has been little need for such high performance in real-world/commercial applications. The drive in the commercial world favours smaller, lower-power, more robust compact atomic clocks that function well in real-world non-laboratory environments. Although the high-performance atomic frequency references are useful to test Einstein's special relativity more precisely, there are not compelling scientific arguments to expect a breakdown in special relativity. On the other hand, the dynamics of gravity, evidenced by the recent spectacular results in experimental detection of gravity waves by the LIGO Scientific Collaboration, shows dramatically that there is new physics to be seen and understood in space-time science. Those systems require strain measurements at less than or equal to 10 -20 As we discuss here, cold atom optical frequency references are still many orders of magnitude away from the frequency stability that should be achievable with narrow-linewidth quantum transitions and large numbers of very cold atoms, and they may be able to achieve levels of phase stability, Δ Φ / Φ total  ≤ 10 -20 , that could make an important impact in gravity wave science.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).

Optical Lattice Bose-Einstein Condensates and the dd Fusion - Iwamura Connection

NASA Astrophysics Data System (ADS)

Chubb, Talbot

2003-03-01

My conjecture: LENR dd fusion occurs in PdDx when a subset of the interstitial deuterons occupy tetrahedral sites in a PdDx crystallite. The tetrahedral deuterons(d's), which occupy shallow potential wells, behave as a superfluid, similar to ultracold Na atoms in shallow-well optical traps, as modeled by Jaksch et al.(D. Jaksch, et al, Phys. Rev. Lett., 81, 3108 (1998).) The tetrahedral d's form a deuteron (d) subsystem, which is neutralized by an electron subsystem containing an equal number of electrons. In the superfluid all the properties of each quasiparticle d are partitioned among N_s_i_te equivalent sites. The partitioning of the d point charge reduces the Coulomb self-repulsion within each quasiparticle pair, which causes wave function overlap at large N_s_i_t_e, allowing d-d fusion. Similarly, partitioning of the point charge of each single quasiparticle d reduces the Coulomb repulsion between it and an obstructing impurity atom, which causes wave function overlap between quasiparticle and atom at large N_s_i_t_e, allowing transmutation of the impurity atom. The Iwamura reaction(Y. Iwamura, et al, Japan J. of Appl. Physics, 41A, 4642 (2002).) is 4 ^2D^+_B_l_o_ch + 4 e^-_B_l_o_ch + ^1^3^3Cs arrow ^1^4^1Pr, with the reaction energy incoherently transferred to the lattice.

Survival resonances in an atom-optics system driven by temporally and spatially periodic dissipation

NASA Astrophysics Data System (ADS)

Chai, Shijie; Fekete, Julia; McDowall, Peter; Coop, Simon; Lindballe, Thue; Andersen, Mikkel F.

2018-03-01

We investigate laser-cooled atoms periodically driven by pulsed standing waves of light tuned close to an open atomic transition. This nonunitary system displays survival resonances for certain driving frequencies. The survival resonances emerge as a result of the matter-wave Talbot-Lau effect, similar to the Talbot effect causing quantum resonances in the atom optics δ -kicked rotor. Since the Talbot-Lau effect occurs for incoherent waves, the survival resonances can be observed using thermal atoms. A microlensing effect can enhance the height and incisiveness of the resonances. This may find applications in precision measurements.

Change in the frequency and intensity of the spectral lines of a hydrogen-like atom in the field of a point charge

NASA Astrophysics Data System (ADS)

Ovsyannikov, V. D.; Kamenskii, A. A.

2002-03-01

The changes in the wave functions and the energies of a hydrogen-like atom in the static field of a structureless charged particle are calculated in the asymptotic approximation. The corrections to the energy of states, as well as to the dipole matrix elements of radiative transitions caused by the interaction of the atom with the point charge at long range are calculated using the perturbation theory and the Sturm series for a reduced Coulomb Green’s function in parabolic coordinates. The analytical expressions are derived and tables of numerical values of the coefficients of asymptotic series that determine the corrections to the matrix elements and the intensities of transitions of the Lyman and Balmer series are presented.

Semi-empirical model for stopping cross sections of p, α and Li ions

NASA Astrophysics Data System (ADS)

Alfaz Uddin, M.; Fazlul Haque, A. K.; Talukder, Tanvir I.; Basak, Arun K.; Saha, Bidhan C.; Malik, Fary B.

2013-10-01

Absolute magnitudes of stopping cross sections (SCS) for H+, He2+ and Li3+ in various stopping media with atomic numbers Z 2 = 2 to 100 are calculated using atomic density functions from Dirac-Hartree-Fock-Slater wave functions in the Lindhard-Schraff theory [J. Lindhard, M. Scharff, Kgl. Danske Videnskab. Selskab. Mat. Fys. Medd. 27, 15 (1953)]. The newly proposed formula, characterizing projectile-specific parameters in the incident energy range considered herein, describes satisfactorily the experimental and SRIM-simulated SCS data from low energies, with projectile velocities nearing v = Z 1 v 0 (with Z 1 as the projectile’s atomic number, v 0 = c / 137, the Bohr velocity and c, the speed of light in vacuum), to high energies up to about 2.5 MeV/u.

Comparing ab initio density-functional and wave function theories: the impact of correlation on the electronic density and the role of the correlation potential.

PubMed

Grabowski, Ireneusz; Teale, Andrew M; Śmiga, Szymon; Bartlett, Rodney J

2011-09-21

The framework of ab initio density-functional theory (DFT) has been introduced as a way to provide a seamless connection between the Kohn-Sham (KS) formulation of DFT and wave-function based ab initio approaches [R. J. Bartlett, I. Grabowski, S. Hirata, and S. Ivanov, J. Chem. Phys. 122, 034104 (2005)]. Recently, an analysis of the impact of dynamical correlation effects on the density of the neon atom was presented [K. Jankowski, K. Nowakowski, I. Grabowski, and J. Wasilewski, J. Chem. Phys. 130, 164102 (2009)], contrasting the behaviour for a variety of standard density functionals with that of ab initio approaches based on second-order Møller-Plesset (MP2) and coupled cluster theories at the singles-doubles (CCSD) and singles-doubles perturbative triples [CCSD(T)] levels. In the present work, we consider ab initio density functionals based on second-order many-body perturbation theory and coupled cluster perturbation theory in a similar manner, for a range of small atomic and molecular systems. For comparison, we also consider results obtained from MP2, CCSD, and CCSD(T) calculations. In addition to this density based analysis, we determine the KS correlation potentials corresponding to these densities and compare them with those obtained for a range of ab initio density functionals via the optimized effective potential method. The correlation energies, densities, and potentials calculated using ab initio DFT display a similar systematic behaviour to those derived from electronic densities calculated using ab initio wave function theories. In contrast, typical explicit density functionals for the correlation energy, such as VWN5 and LYP, do not show behaviour consistent with this picture of dynamical correlation, although they may provide some degree of correction for already erroneous explicitly density-dependent exchange-only functionals. The results presented here using orbital dependent ab initio density functionals show that they provide a treatment of exchange and correlation contributions within the KS framework that is more consistent with traditional ab initio wave function based methods.

Non-autonomous matter-wave solitons in hybrid atomic-molecular Bose-Einstein condensates with tunable interactions and harmonic potential

NASA Astrophysics Data System (ADS)

Wang, Deng-Shan; Liu, Jiang; Wang, Lizhen

2018-03-01

In this paper, we investigate matter-wave solitons in hybrid atomic-molecular Bose-Einstein condensates with tunable interactions and external potentials. Three types of time-modulated harmonic potentials are considered and, for each of them, two groups of exact non-autonomous matter-wave soliton solutions of the coupled Gross-Pitaevskii equation are presented. Novel nonlinear structures of these non-autonomous matter-wave solitons are analyzed by displaying their density distributions. It is shown that the time-modulated nonlinearities and external potentials can support exact non-autonomous atomic-molecular matter-wave solitons.

Resonance fluorescence microscopy via three-dimensional atom localization

NASA Astrophysics Data System (ADS)

Panchadhyayee, Pradipta; Dutta, Bibhas Kumar; Das, Nityananda; Mahapatra, Prasanta Kumar

2018-02-01

A scheme is proposed to realize three-dimensional (3D) atom localization in a driven two-level atomic system via resonance fluorescence. The field arrangement for the atom localization involves the application of three mutually orthogonal standing-wave fields and an additional traveling-wave coupling field. We have shown the efficacy of such field arrangement in tuning the spatially modulated resonance in all directions. Under different parametric conditions, the 3D localization patterns originate with various shapes such as sphere, sheets, disk, bowling pin, snake flute, flower vase. High-precision localization is achieved when the radiation field detuning equals twice the combined Rabi frequencies of the standing-wave fields. Application of a traveling-wave field of suitable amplitude at optimum radiation field detuning under symmetric standing-wave configuration leads to 100% detection probability even in sub-wavelength domain. Asymmetric field configuration is also taken into consideration to exhibit atom localization with appreciable precision compared to that of the symmetric case. The momentum distribution of the localized atoms is found to follow the Heisenberg uncertainty principle under the validity of Raman-Nath approximation. The proposed field configuration is suitable for application in the study of atom localization in an optical lattice arrangement.

Atomic data for a five-configuration model of Fe XIV

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Kastner, S. O.

1993-01-01

Collision strengths calculated in the distorted wave approximation are presented for electron excitation of Fe XIV at incident energies of 10, 20 and 30 Rydbergs. Configurations 3s(2)3p, 3s3p(2), 3s(2)3d, 3p(3), and 3s3p3d are included, comprising 40 levels, and wave function mixing coefficients are tabulated. Radiative transition rates are given for the same model using the Superstructure program.

Coherence in the presence of absorption and heating in a molecule interferometer

PubMed Central

Cotter, J. P.; Eibenberger, S.; Mairhofer, L.; Cheng, X.; Asenbaum, P.; Arndt, M.; Walter, K.; Nimmrichter, S.; Hornberger, K.

2015-01-01

Matter-wave interferometry can be used to probe the foundations of physics and to enable precise measurements of particle properties and fundamental constants. It relies on beam splitters that coherently divide the wave function. In atom interferometers, such elements are often realised using lasers by exploiting the dipole interaction or through photon absorption. It is intriguing to extend these ideas to complex molecules where the energy of an absorbed photon can rapidly be redistributed across many internal degrees of freedom. Here, we provide evidence that center-of-mass coherence can be maintained even when the internal energy and entropy of the interfering particle are substantially increased by absorption of photons from a standing light wave. Each photon correlates the molecular center-of-mass wave function with its internal temperature and splits it into a superposition with opposite momenta in addition to the beam-splitting action of the optical dipole potential. PMID:26066053

Design of graphene nanoparticle undergoing axial compression: quantum study

NASA Astrophysics Data System (ADS)

Glukhova, O. E.; Kirillova, I. V.; Saliy, I. N.; Kolesnikova, A. S.; Slepchenkov, M. M.

2011-03-01

We report the results of quantum mechanical investigations of the atomic structure and deformations of graphene nanoparticle undergoing axial compression. We applied the tight-binding (TB) method. Our transferable tightbinding potential correctly reproduced tight-binding changes in the electronic configuration as a function of the local bonding geometry around each carbon atom. The tight-binding method applied provided the consideration and calculation of the rehybridization between σ- and π-orbitals. To research nanoribbons using tight-binding potential our own program was used. We adapted TB method to be able to run the algorithm on a parallel computing machine (computer cluster). To simulate axial compression of graphene nanoparticles the atoms on the ends were fixed on the plates. The plates were moved towards each other to decrease the length at some percent. Plane atomic network undergoing axial compression became wave-like. The amplitude of wave and its period were not constant and changed along axis. This is a phase transition. The strain energy collapse occurs at the value of axial compression 0.03-0.04. The strain energy increased up to the quantity compression 0.03, then collapsed sharply and decreased. So according to our theoretical investigation, the elasticity of graphene nanoparticles is more than the elasticity of nanotubes the same width and length. The curvature of the atomic network because of compression will decrease the reactivity of graphene nanoparticles. We have calculated the atomic structure and electronic structure of the compression graphene nanopaticle at each step of strain of axial compression. We have come to the conclusion that the wave-like graphenes adsorbing protein and nucleic acid are the effective nanosensors and bionanosensors.

Composite pulses for interferometry in a thermal cold atom cloud

NASA Astrophysics Data System (ADS)

Dunning, Alexander; Gregory, Rachel; Bateman, James; Cooper, Nathan; Himsworth, Matthew; Jones, Jonathan A.; Freegarde, Tim

2014-09-01

Atom interferometric sensors and quantum information processors must maintain coherence while the evolving quantum wave function is split, transformed, and recombined, but suffer from experimental inhomogeneities and uncertainties in the speeds and paths of these operations. Several error-correction techniques have been proposed to isolate the variable of interest. Here we apply composite pulse methods to velocity-sensitive Raman state manipulation in a freely expanding thermal atom cloud. We compare several established pulse sequences, and follow the state evolution within them. The agreement between measurements and simple predictions shows the underlying coherence of the atom ensemble, and the inversion infidelity in a ˜80μK atom cloud is halved. Composite pulse techniques, especially if tailored for atom interferometric applications, should allow greater interferometer areas, larger atomic samples, and longer interaction times, and hence improve the sensitivity of quantum technologies from inertial sensing and clocks to quantum information processors and tests of fundamental physics.

Atomic Interferometric Gravitational-Wave Space Observatory (AIGSO)

NASA Astrophysics Data System (ADS)

Gao, Dong-Feng; Wang, Jin; Zhan, Ming-Sheng

2018-01-01

We propose a space-borne gravitational-wave detection scheme, called atom interferometric gravitational-wave space observatory (AIGSO). It is motivated by the progress in the atomic matter-wave interferometry, which solely utilizes the standing light waves to split, deflect and recombine the atomic beam. Our scheme consists of three drag-free satellites orbiting the Earth. The phase shift of AIGSO is dominated by the Sagnac effect of gravitational-waves, which is proportional to the area enclosed by the atom interferometer, the frequency and amplitude of gravitational-waves. The scheme has a strain sensitivity < {10}-20/\\sqrt{{Hz}} in the 100 mHz-10 Hz frequency range, which fills in the detection gap between space-based and ground-based laser interferometric detectors. Thus, our proposed AIGSO can be a good complementary detection scheme to the space-borne laser interferometric schemes, such as LISA. Considering the current status of relevant technology readiness, we expect our AIGSO to be a promising candidate for the future space-based gravitational-wave detection plan. Supported by the National Key Research Program of China under Grant No. 2016YFA0302002, the National Science Foundation of China under Grant Nos. 11227803 and 91536221, and the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No. XDB21010100

Optical potential approach to the electron-atom impact ionization threshold problem

NASA Technical Reports Server (NTRS)

Temkin, A.; Hahn, Y.

1973-01-01

The problem of the threshold law for electron-atom impact ionization is reconsidered as an extrapolation of inelastic cross sections through the ionization threshold. The cross sections are evaluated from a distorted wave matrix element, the final state of which describes the scattering from the Nth excited state of the target atom. The actual calculation is carried for the e-H system, and a model is introduced which is shown to preserve the essential properties of the problem while at the same time reducing the dimensionability of the Schrodinger equation. Nevertheless, the scattering equation is still very complex. It is dominated by the optical potential which is expanded in terms of eigen-spectrum of QHQ. It is shown by actual calculation that the lower eigenvalues of this spectrum descend below the relevant inelastic thresholds; it follows rigorously that the optical potential contains repulsive terms. Analytical solutions of the final state wave function are obtained with several approximations of the optical potential.

Interactions and low-energy collisions between an alkali ion and an alkali atom of a different nucleus

NASA Astrophysics Data System (ADS)

Rakshit, Arpita; Ghanmi, Chedli; Berriche, Hamid; Deb, Bimalendu

2016-05-01

We study theoretically interaction potentials and low-energy collisions between different alkali atoms and alkali ions. Specifically, we consider systems such as X + {{{Y}}}+, where X({{{Y}}}+) is either Li(Cs+) or Cs(Li+), Na(Cs+) or Cs(Na+) and Li(Rb+) or Rb(Li+). We calculate the molecular potentials of the ground and first two excited states of these three systems using a pseudopotential method and compare our results with those obtained by others. We derive ground-state scattering wave functions and analyze the cold collisional properties of these systems for a wide range of energies. We find that, in order to get convergent results for the total scattering cross sections for energies of the order 1 K, one needs to take into account at least 60 partial waves. The low-energy scattering properties calculated in this paper may serve as a precursor for experimental exploration of quantum collisions between an alkali atom and an alkali ion of a different nucleus.

Review of Quantum Electromagnetic States

DTIC Science & Technology

1999-10-01

product space. 227 The wave functions used in the Jaynes - Cummings ’ model reside in a direct product space Va ɠ> Vf where Va and Vf are the Hubert...Dependent Probability 215 5.1.3 The Relaxation Term 217 5.2 Jaynes - Cummings ’ Model for Matter-Field Interactions 218 5.2.1 The Atomic Hamiltonian 218...5.3 The Interaction Representation for the Jaynes - Cummings ’ Model 224 5.3.1 Atomic Creation and Annihilation Operators 224 5.3.2 The Boson Creation

Bloch equation and atom-field entanglement scenario in three-level systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, Surajit; Nath, Mihir Ranjan; Dey, Tushar Kanti

2011-09-23

We study the exact solution of the lambda, vee and cascade type of three-level system with distinct Hamiltonian for each configuration expressed in the SU(3) basis. The semiclassical models are solved by solving respective Bloch equation and the existence of distinct non-linear constants are discussed which are different for different configuration. Apart from proposing a qutrit wave function, the atom-field entanglement is studied for the quantized three-level systems using the Phoenix-Knight formalism and corresponding population inversion are compared.

Kinetic theory of weakly ionized dilute gas of hydrogen-like atoms of the first principles of quantum statistics and dispersion laws of eigenwaves

NASA Astrophysics Data System (ADS)

Slyusarenko, Yurii V.; Sliusarenko, Oleksii Yu.

2017-11-01

We develop a microscopic approach to the construction of the kinetic theory of dilute weakly ionized gas of hydrogen-like atoms. The approach is based on the statements of the second quantization method in the presence of bound states of particles. The basis of the derivation of kinetic equations is the method of reduced description of relaxation processes. Within the framework of the proposed approach, a system of common kinetic equations for the Wigner distribution functions of free oppositely charged fermions of two kinds (electrons and cores) and their bound states—hydrogen-like atoms— is obtained. Kinetic equations are used to study the spectra of elementary excitations in the system when all its components are non-degenerate. It is shown that in such a system, in addition to the typical plasma waves, there are longitudinal waves of matter polarization and the transverse ones with a behavior characteristic of plasmon polaritons. The expressions for the dependence of the frequencies and Landau damping coefficients on the wave vector for all branches of the oscillations discovered are obtained. Numerical evaluation of the elementary perturbation parameters in the system on an example of a weakly ionized dilute gas of the 23Na atoms using the D2-line characteristics of the natrium atom is given. We note the possibility of using the results of the developed theory to describe the properties of a Bose condensate of photons in the diluted weakly ionized gas of hydrogen-like atoms.

On the non-linear spectroscopy including saturated absorption and four-wave mixing in two and multi-level atoms: a computational study

NASA Astrophysics Data System (ADS)

Patel, M.; De Jager, G.; Nkosi, Z.; Wyngaard, A.; Govender, K.

2017-10-01

In this paper we report on the study of two and multi-level atoms interacting with multiple laser beams. The semi-classical approach is used to describe the system in which the atoms are treated quantum mechanically via the density matrix operator, while the laser beams are treated classically using Maxwells equations. We present results of a two level atom interacting with single and multiple laser beams and demonstrate Rabi oscillations between the levels. The effects of laser modulation on the dynamics of the atom (atomic populations and coherences) are examined by solving the optical Bloch equations. Plots of the density matrix elements as a function of time are presented for various parameters such as laser intensity, detuning, modulation etc. In addition, phase-space plots and Fourier analysis of the density matrix elements are provided. The atomic polarization, estimated from the coherence terms of the density matrix elements, is used in the numerical solution of Maxwells equations to determine the behaviour of the laser beams as they propagate through the atomic ensemble. The effects of saturation and hole-burning are demonstrated in the case of two counter propagating beams with one being a strong beam and the other being very weak. The above work is extended to include four-wave mixing in four level atoms in a diamond configuration. Two co-propagating beams of different wavelengths drive the atoms from a ground state |1〉 to an excited state |3〉 via an intermediate state |2〉. The atoms then move back to the ground state via another intermediate state |4〉, resulting in the generation of two additional correlated photon beams. The characteristics of these additional photons are studied.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowan, R. D.; Rajnak, K.; Renard, P.

This is a set of three Fortran IV programs, RCN29, HFMOD7, and RCN229, based on the Herman--Skillman and Charlotte Froese Fischer programs, with extensive modifications and additions. The programs compute self-consistent-field radial wave functions and the various radial integrals involved in the computation of atomic energy levels and spectra.

Wave-function-renormalization effects in resonantly enhanced tunneling

NASA Astrophysics Data System (ADS)

Lörch, N.; Pepe, F. V.; Lignier, H.; Ciampini, D.; Mannella, R.; Morsch, O.; Arimondo, E.; Facchi, P.; Florio, G.; Pascazio, S.; Wimberger, S.

2012-05-01

We study the time evolution of ultracold atoms in an accelerated optical lattice. For a Bose-Einstein condensate with a narrow quasimomentum distribution in a shallow optical lattice the decay of the survival probability in the ground band has a steplike structure. In this regime we establish a connection between the wave-function-renormalization parameter Z introduced by P. Facchi, H. Nakazato, and S. Pascazio [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.86.2699 86, 2699 (2001)] to characterize nonexponential decay and the phenomenon of resonantly enhanced tunneling, where the decay rate is peaked for particular values of the lattice depth and the accelerating force.

Decoherence and Determinism in a One-Dimensional Cloud-Chamber Model

NASA Astrophysics Data System (ADS)

Sparenberg, Jean-Marc; Gaspard, David

2018-03-01

The hypothesis (Sparenberg et al. in EPJ Web Conf 58:01016, [1]. https://doi.org/10.1051/epjconf/20135801016) that the particular linear tracks appearing in the measurement of a spherically-emitting radioactive source in a cloud chamber are determined by the (random) positions of atoms or molecules inside the chamber is further explored in the framework of a recently established one-dimensional model (Carlone et al. Comm Comput Phys 18:247, [2]. https://doi.org/10.4208/cicp.270814.311214a). In this model, meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the spherical wave is replaced by a linear superposition of two wave packets moving from the origin to the left and to the right, evolving deterministically according to the Schrödinger equation. We first revisit these results using a time-dependent approach, where the wave packets impinge on a symmetric two-sided detector. We discuss the evolution of the wave function in the configuration space and stress the interest of a non-symmetric detector in a quantum-measurement perspective. Next we use a time-independent approach to study the scattering of a plane wave on a single-sided detector. Preliminary results are obtained, analytically for the single-spin case and numerically for up to 8 spins. They show that the spin-excitation probabilities are sometimes very sensitive to the parameters of the model, which corroborates the idea that the measurement result could be determined by the atom positions. The possible origin of decoherence and entropy increase in future models is finally discussed.

Multielectron effects in the photoelectron momentum distribution of noble-gas atoms driven by visible-to-infrared-frequency laser pulses: A time-dependent density-functional-theory approach

NASA Astrophysics Data System (ADS)

Murakami, Mitsuko; Zhang, G. P.; Chu, Shih-I.

2017-05-01

We present the photoelectron momentum distributions (PMDs) of helium, neon, and argon atoms driven by a linearly polarized, visible (527-nm) or near-infrared (800-nm) laser pulse (20 optical cycles in duration) based on the time-dependent density-functional theory (TDDFT) under the local-density approximation with a self-interaction correction. A set of time-dependent Kohn-Sham equations for all electrons in an atom is numerically solved using the generalized pseudospectral method. An effect of the electron-electron interaction driven by a visible laser field is not recognizable in the helium and neon PMDs except for a reduction of the overall photoelectron yield, but there is a clear difference between the PMDs of an argon atom calculated with the frozen-core approximation and TDDFT, indicating an interference of its M -shell wave functions during the ionization. Furthermore, we find that the PMDs of degenerate p states are well separated in intensity when driven by a near-infrared laser field, so that the single-active-electron approximation can be adopted safely.

Configurational forces in electronic structure calculations using Kohn-Sham density functional theory

NASA Astrophysics Data System (ADS)

Motamarri, Phani; Gavini, Vikram

2018-04-01

We derive the expressions for configurational forces in Kohn-Sham density functional theory, which correspond to the generalized variational force computed as the derivative of the Kohn-Sham energy functional with respect to the position of a material point x . These configurational forces that result from the inner variations of the Kohn-Sham energy functional provide a unified framework to compute atomic forces as well as stress tensor for geometry optimization. Importantly, owing to the variational nature of the formulation, these configurational forces inherently account for the Pulay corrections. The formulation presented in this work treats both pseudopotential and all-electron calculations in a single framework, and employs a local variational real-space formulation of Kohn-Sham density functional theory (DFT) expressed in terms of the nonorthogonal wave functions that is amenable to reduced-order scaling techniques. We demonstrate the accuracy and performance of the proposed configurational force approach on benchmark all-electron and pseudopotential calculations conducted using higher-order finite-element discretization. To this end, we examine the rates of convergence of the finite-element discretization in the computed forces and stresses for various materials systems, and, further, verify the accuracy from finite differencing the energy. Wherever applicable, we also compare the forces and stresses with those obtained from Kohn-Sham DFT calculations employing plane-wave basis (pseudopotential calculations) and Gaussian basis (all-electron calculations). Finally, we verify the accuracy of the forces on large materials systems involving a metallic aluminum nanocluster containing 666 atoms and an alkane chain containing 902 atoms, where the Kohn-Sham electronic ground state is computed using a reduced-order scaling subspace projection technique [P. Motamarri and V. Gavini, Phys. Rev. B 90, 115127 (2014), 10.1103/PhysRevB.90.115127].

Search for light scalar dark matter with atomic gravitational wave detectors

NASA Astrophysics Data System (ADS)

Arvanitaki, Asimina; Graham, Peter W.; Hogan, Jason M.; Rajendran, Surjeet; Van Tilburg, Ken

2018-04-01

We show that gravitational wave detectors based on a type of atom interferometry are sensitive to ultralight scalar dark matter. Such dark matter can cause temporal oscillations in fundamental constants with a frequency set by the dark matter mass and amplitude determined by the local dark matter density. The result is a modulation of atomic transition energies. We point out a new time-domain signature of this effect in a type of gravitational wave detector that compares two spatially separated atom interferometers referenced by a common laser. Such a detector can improve on current searches for electron-mass or electric-charge modulus dark matter by up to 10 orders of magnitude in coupling, in a frequency band complementary to that of other proposals. It demonstrates that this class of atomic sensors is qualitatively different from other gravitational wave detectors, including those based on laser interferometry. By using atomic-clock-like interferometers, laser noise is mitigated with only a single baseline. These atomic sensors can thus detect scalar signals in addition to tensor signals.

Ultrasonic atomization of liquids in drop-chain acoustic fountains

PubMed Central

Simon, Julianna C.; Sapozhnikov, Oleg A.; Khokhlova, Vera A.; Crum, Lawrence A.; Bailey, Michael R.

2015-01-01

When focused ultrasound waves of moderate intensity in liquid encounter an air interface, a chain of drops emerges from the liquid surface to form what is known as a drop-chain fountain. Atomization, or the emission of micro-droplets, occurs when the acoustic intensity exceeds a liquid-dependent threshold. While the cavitation-wave hypothesis, which states that atomization arises from a combination of capillary-wave instabilities and cavitation bubble oscillations, is currently the most accepted theory of atomization, more data on the roles of cavitation, capillary waves, and even heat deposition or boiling would be valuable. In this paper, we experimentally test whether bubbles are a significant mechanism of atomization in drop-chain fountains. High-speed photography was used to observe the formation and atomization of drop-chain fountains composed of water and other liquids. For a range of ultrasonic frequencies and liquid sound speeds, it was found that the drop diameters approximately equalled the ultrasonic wavelengths. When water was exchanged for other liquids, it was observed that the atomization threshold increased with shear viscosity. Upon heating water, it was found that the time to commence atomization decreased with increasing temperature. Finally, water was atomized in an overpressure chamber where it was found that atomization was significantly diminished when the static pressure was increased. These results indicate that bubbles, generated by either acoustic cavitation or boiling, contribute significantly to atomization in the drop-chain fountain. PMID:25977591

Influence of the frequency detuning on the four-wave mixing efficiency in three-level system coupled by standing-wave

NASA Astrophysics Data System (ADS)

Zhou, Hai-Tao; Che, Shao-Na; Han, Yu-Hong; Wang, Dan

2018-05-01

In a Λ-type three-level atomic system coupled by an off-resonant standing-wave, the reflected four-wave mixing (FWM) spectrum is studied. It shows that the maximum reflection efficiency occurs when both of the coupling and probe fields are tuned off resonances from the atomic transitions. The essence of enhanced reflection is that the nonlinear efficiency of the FWM based on coherent atoms is improved due to the significant reduction of phase mismatch. The theoretical analysis shows good agreement with the experimental results. Furthermore, the influence of the atomic number density on the coupling frequency detuning of the optimum reflection efficiency and the linewidth are also investigated.

Neutral-atom electron binding energies from relaxed-orbital relativistic Hartree-Fock-Slater calculations for Z between 2 and 106

NASA Technical Reports Server (NTRS)

Huang, K.-N.; Aoyagi, M.; Mark, H.; Chen, M. H.; Crasemann, B.

1976-01-01

Electron binding energies in neutral atoms have been calculated relativistically, with the requirement of complete relaxation. Hartree-Fock-Slater wave functions served as zeroth-order eigenfunctions to compute the expectation of the total Hamiltonian. A first-order correction to the local approximation was thus included. Quantum-electrodynamic corrections were made. For all elements with atomic numbers ranging from 2 to 106, the following quantities are listed: total energies, electron kinetic energies, electron-nucleus potential energies, electron-electron potential energies consisting of electrostatic and Breit interaction (magnetic and retardation) terms, and vacuum polarization energies. Binding energies including relaxation are listed for all electrons in all atoms over the indicated range of atomic numbers. A self-energy correction is included for the 1s, 2s, and 2p(1/2) levels. Results for selected atoms are compared with energies calculated by other methods and with experimental values.

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17)/cu cm. The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3x10(exp 17) and 9x10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

NASA Technical Reports Server (NTRS)

Meyer, Scott Andrew

1995-01-01

The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

Photoionization of Atoms and Molecules using a Configuration-Average Distorted-Wave Method

NASA Astrophysics Data System (ADS)

Pindzola, M. S.; Balance, C. P.; Loch, S. D.; Ludlow, J. A.

2011-05-01

A configuration-average distorted-wave method is applied to calculate the photoionization cross section for the outer subshells of the C atom and the C2 diatomic molecule. Comparisions are made with previous R-matrix and Hartree- Fock distorted-wave calculations.

DFT calculations for Au adsorption onto a reduced TiO2 (110) surface with the coexistence of Cl

NASA Astrophysics Data System (ADS)

Tada, Kohei; Sakata, Kohei; Yamada, Satoru; Okazaki, Kazuyuki; Kitagawa, Yasutaka; Kawakami, Takashi; Yamanaka, Shusuke; Okumura, Mitsutaka

2014-02-01

Residual chlorines, which originate from HAuCl4, enhance the aggregation of gold (Au) nanoparticles and clusters, preventing the generation of highly active supported Au catalysts. However, the detailed mechanism of residual-chlorine-promoted aggregation of Au is unknown. Herein to investigate this mechanism, density functional theory (DFT) calculations of Au and Cl adsorption onto a reduced rutile TiO2 (110) surface were performed using a generalised gradient approximation Perdew, Burke, and Ernzerhof formula (GGA-PBE) functional and plane-wave basis. Although both Au and Cl atoms prefer to mono-absorb onto oxygen defect sites, Cl atoms have a stronger absorption onto a reduced TiO2 (110) surface, abbreviated as rTiO2 (110) in the following, than Au atoms. Additionally, co-adsorption of a Cl atom and a Au atom or Au nanorod onto a rTiO2 surface was investigated; Cl adsorption onto an oxygen defect site weakens the interaction between a Au atom or Au nanorod and rTiO2 (110) surface. The calculation results suggest that the depletion of interaction between Au and rTiO2 surface is due to strong interaction between Cl atoms at oxygen defect sites and neighbouring bridging oxygen (OB) atoms.

Exotic topological density waves in cold atomic Rydberg-dressed fermions

PubMed Central

Li, Xiaopeng; Sarma, S Das

2015-01-01

Versatile controllability of interactions in ultracold atomic and molecular gases has now reached an era where quantum correlations and unconventional many-body phases can be studied with no corresponding analogues in solid-state systems. Recent experiments in Rydberg atomic gases have achieved exquisite control over non-local interactions, allowing novel quantum phases unreachable with the usual local interactions in atomic systems. Here we study Rydberg-dressed atomic fermions in a three-dimensional optical lattice predicting the existence of hitherto unheard-of exotic mixed topological density wave phases. By varying the spatial range of the non-local interaction, we find various chiral density waves with spontaneous time-reversal symmetry breaking, whose quasiparticles form three-dimensional quantum Hall and Weyl semimetal states. Remarkably, certain density waves even exhibit mixed topologies beyond the existing topological classification. Our results suggest gapless fermionic states could exhibit far richer topology than previously expected. PMID:25972134

Ultralong-range Rydberg Molecules: Investigation of a Novel Binding Mechanism

NASA Astrophysics Data System (ADS)

Butscher, Björn; Bendkowsky, Vera; Nipper, Johannes; Balewski, Jonathan; Shaffer, James P.; Löw, Robert; Pfau, Tilman

2010-03-01

For highly excited Rydberg atoms, the scattering of the Rydberg electron from a nearby polarizable ground state atom can generate an attractive mean-field potential which is able to bind the ground state atom to the Rydberg atom within the Rydberg electron wave function at binding energies ranging from a few MHz to hundreds of MHz[1]. We present spectroscopic data on the observation of various bound states including the vibrational ground and excited states of rubidium dimers Rb(5S)-Rb(nS) as well as those of trimer states. Furthermore, we show calculations that reproduce the observed binding energies remarkably well and reveal that some of the excited states are purely bound by quantum reflection at a shape resonance for p-wave scattering [2]. To further characterize the coherent excitation of the molecular states, we performed echo experiments. [0pt] [1] V. Bendkowsky, B. Butscher, J. Nipper, J. P. Shaffer, R. Löw, T. Pfau, Nature 458, 1005 (2009); [2] V. Bendkowsky, B. Butscher, J. Nipper, J. Balewski, J. P. Shaffer, R. Löw, T. Pfau, W. Li, J. Stanojevic, T. Pohl,and J. M. Rost, arXiv:0912.4058 (2009)

Atomic structure calculations and identification of EUV and SXR spectral lines in Sr XXX

NASA Astrophysics Data System (ADS)

Goyal, Arun; Khatri, Indu; Aggarwal, Sunny; Singh, A. K.; Mohan, Man

2015-08-01

We report an extensive theoretical study of atomic data for Sr XXX in a wide range with L-shell electron excitations to the M-shell. We have calculated energy levels, wave-function compositions and lifetimes for lowest 113 fine structure levels and wavelengths of an extreme Ultraviolet (EUV) and soft X-ray (SXR) transitions. We have employed multi-configuration Dirac Fock method (MCDF) approach within the framework of Dirac-Coulomb Hamiltonian including quantum electrodynamics (QED) and Breit corrections. We have also presented the radiative data for electric and magnetic dipole (E1, M1) and quadrupole (E2, M2) transitions from the ground state. We have made comparisons with available energy levels compiled by NIST and achieve good agreement. But due to inadequate data in the literature, analogous relativistic distorted wave calculations have also been performed using flexible atomic code (FAC) to assess the reliability and accuracy of our results. Additionally, we have provided new atomic data for Sr XXX which is not published elsewhere in the literature and we believe that our results may be beneficial in fusion plasma research and astrophysical investigations and applications.

Full quantum mechanical analysis of atomic three-grating Mach–Zehnder interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanz, A.S., E-mail: asanz@iff.csic.es; Davidović, M.; Božić, M.

2015-02-15

Atomic three-grating Mach–Zehnder interferometry constitutes an important tool to probe fundamental aspects of the quantum theory. There is, however, a remarkable gap in the literature between the oversimplified models and robust numerical simulations considered to describe the corresponding experiments. Consequently, the former usually lead to paradoxical scenarios, such as the wave–particle dual behavior of atoms, while the latter make difficult the data analysis in simple terms. Here these issues are tackled by means of a simple grating working model consisting of evenly-spaced Gaussian slits. As is shown, this model suffices to explore and explain such experiments both analytically and numerically,more » giving a good account of the full atomic journey inside the interferometer, and hence contributing to make less mystic the physics involved. More specifically, it provides a clear and unambiguous picture of the wavefront splitting that takes place inside the interferometer, illustrating how the momentum along each emerging diffraction order is well defined even though the wave function itself still displays a rather complex shape. To this end, the local transverse momentum is also introduced in this context as a reliable analytical tool. The splitting, apart from being a key issue to understand atomic Mach–Zehnder interferometry, also demonstrates at a fundamental level how wave and particle aspects are always present in the experiment, without incurring in any contradiction or interpretive paradox. On the other hand, at a practical level, the generality and versatility of the model and methodology presented, makes them suitable to attack analogous problems in a simple manner after a convenient tuning. - Highlights: • A simple model is proposed to analyze experiments based on atomic Mach–Zehnder interferometry. • The model can be easily handled both analytically and computationally. • A theoretical analysis based on the combination of the position and momentum representations is considered. • Wave and particle aspects are shown to coexist within the same experiment, thus removing the old wave-corpuscle dichotomy. • A good agreement between numerical simulations and experimental data is found without appealing to best-fit procedures.« less

Algebraic tools for dealing with the atomic shell model. I. Wavefunctions and integrals for hydrogen-like ions

NASA Astrophysics Data System (ADS)

Surzhykov, Andrey; Koval, Peter; Fritzsche, Stephan

2005-01-01

Today, the 'hydrogen atom model' is known to play its role not only in teaching the basic elements of quantum mechanics but also for building up effective theories in atomic and molecular physics, quantum optics, plasma physics, or even in the design of semiconductor devices. Therefore, the analytical as well as numerical solutions of the hydrogen-like ions are frequently required both, for analyzing experimental data and for carrying out quite advanced theoretical studies. In order to support a fast and consistent access to these (Coulomb-field) solutions, here we present the DIRAC program which has been developed originally for studying the properties and dynamical behavior of the (hydrogen-like) ions. In the present version, a set of MAPLE procedures is provided for the Coulomb wave and Green's functions by applying the (wave) equations from both, the nonrelativistic and relativistic theory. Apart from the interactive access to these functions, moreover, a number of radial integrals are also implemented in the DIRAC program which may help the user to construct transition amplitudes and cross sections as they occur frequently in the theory of ion-atom and ion-photon collisions. Program summaryTitle of program:DIRAC Catalogue number: ADUQ Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUQ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: None Computer for which the program is designed and has been tested: All computers with a license of the computer algebra package MAPLE [1] Program language used: Maple 8 and 9 No. of lines in distributed program, including test data, etc.:2186 No. of bytes in distributed program, including test data, etc.: 162 591 Distribution format: tar gzip file CPC Program Library subprograms required: None Nature of the physical problem: Analytical solutions of the hydrogen atom are widely used in very different fields of physics [2,3]. Despite of the rather simple structure of the hydrogen-like ions, however, the underlying 'mathematics' is not always that easy to deal with. Apart from the well-known level structure of these ions as obtained from either the Schrödinger or Dirac equation, namely, a great deal of other properties are often needed. These properties are related to the interaction of bound electron(s) with external particles and fields and, hence, require to evaluate transition amplitudes, including wavefunctions and (transition) operators of quite different complexity. Although various special functions, such as the Laguerre polynomials, spherical harmonics, Whittaker functions, or the hypergeometric functions of various kinds can be used in most cases in order to express these amplitudes in a concise form, their derivation is time consuming and prone for making errors. In addition to their complexity, moreover, there exist a large number of mathematical relations among these functions which are difficult to remember in detail and which have often hampered quantitative studies in the past. Method of solution: A set of MAPLE procedures is developed which provides both the nonrelativistic and relativistic (analytical) solutions of the 'hydrogen atom model' and which facilitates the symbolic evaluation of various transition amplitudes. Restrictions onto the complexity of the problem: Over the past decades, a large number of representations have been worked out for the hydrogenic wave and Green's functions, using different variables and coordinates [2]. From these, the position-space representation in spherical coordinates is certainly of most practical interest and has been used as the basis of the present implementation. No attempt has been made by us so far to provide the wave and Green's functions also in momentum space, for which the relativistic momentum functions would have to be constructed numerically. Although the DIRAC program supports both symbolic and numerical computations, the latter one are based on MAPLE's standard software floating-point algorithms and on the (attempted) precision as defined by the global Digits variable. Although the default number, Digits = 10, appears sufficient for many computations, it often leads to a rather dramatic loss in the accuracy of the relativistic wave functions and integrals, mainly owing to MAPLE's imprecise internal evaluation of the corresponding special functions. Therefore, in order to avoid such computational difficulties, the Digits variable is set to 20 whenever the DIRAC program is (re-)loaded. Unusual features of the program: The DIRAC program has been designed for interactive work which, apart from the standard solutions and integrals of the hydrogen atom, also support the use of (approximate) semirelativistic wave functions for both, the bound- and continuum-states of the electron. To provide a fast and accurate access to a number of radial integrals which arise frequently in applications, the analytical expressions for these integrals have been implemented for the one-particle operators r, e, d/dr, j(kr) as well as for the (so-called) two-particle Slater integrals which are needed to describe the Coulomb repulsion among the electrons. Further procedures of the DIRAC program concern, for instance, the conversion of the physical results between different unit systems or for different sets of quantum numbers. A brief description of all procedures as available in the present version of the DIRAC program is given in the user manual Dirac-commands.pdf which is distributed together with the code. Typical running time: Although the program replies promptly on most requests, the running time also depends on the particular task. References: [1] Maple is a registered trademark of Waterloo Maple Inc. [2] H.A. Bethe and E.E. Salpeter, Quantum Mechanics of One- and Two-Electron Atoms, Springer, Berlin, 1957. [3] J. Eichler and W. Meyerhof, Relativistic Atomic Collisions, Academic Press, New York, 1995.

Speckle reduction in optical coherence tomography images based on wave atoms

PubMed Central

Du, Yongzhao; Liu, Gangjun; Feng, Guoying; Chen, Zhongping

2014-01-01

Abstract. Optical coherence tomography (OCT) is an emerging noninvasive imaging technique, which is based on low-coherence interferometry. OCT images suffer from speckle noise, which reduces image contrast. A shrinkage filter based on wave atoms transform is proposed for speckle reduction in OCT images. Wave atoms transform is a new multiscale geometric analysis tool that offers sparser expansion and better representation for images containing oscillatory patterns and textures than other traditional transforms, such as wavelet and curvelet transforms. Cycle spinning-based technology is introduced to avoid visual artifacts, such as Gibbs-like phenomenon, and to develop a translation invariant wave atoms denoising scheme. The speckle suppression degree in the denoised images is controlled by an adjustable parameter that determines the threshold in the wave atoms domain. The experimental results show that the proposed method can effectively remove the speckle noise and improve the OCT image quality. The signal-to-noise ratio, contrast-to-noise ratio, average equivalent number of looks, and cross-correlation (XCOR) values are obtained, and the results are also compared with the wavelet and curvelet thresholding techniques. PMID:24825507

Elastic scattering of X-rays and gamma rays by 2S electrons in ions and neutral atoms

NASA Astrophysics Data System (ADS)

Costescu, A.; Spânulescu, S.; Stoica, C.

2012-08-01

The nonrelativistic limit of Rayleigh scattering amplitude on 2s electrons of neutral and partially ionized atoms is obtained by making use of the Green Function method. The result takes into consideration the retardation, relativistic kinematics and screening effects. The spurious singularities introduced by the retardation in a nonrelativistic approach are cancelled by the relativistic kinematics. For neutral and partially ionized atoms, a screening model is considered with an effective charge obtained by fitting the Hartree-Fock charge distribution with pure Coulombian wave functions corresponding to a central potential of a nucleus with Zeff as the atomic number. The total cross section of the photoeffect on the 2s electrons is also calculated from the imaginary part of the forward scattering amplitude by means of the optical theorem. The numerical results obtained are in a good agreement (10%) with the ones obtained by Kissell for the Rayleigh amplitude and by Scofield for the Photoeffect total cross section on the 2s electrons, for atoms with atomic number 18 ≤ Z ≤ 92 and photon energies ω≤αZm. (α=1/137,... is the fine structure constant, m is the electron mass).

Variational treatment of electron-polyatomic-molecule scattering calculations using adaptive overset grids

NASA Astrophysics Data System (ADS)

Greenman, Loren; Lucchese, Robert R.; McCurdy, C. William

2017-11-01

The complex Kohn variational method for electron-polyatomic-molecule scattering is formulated using an overset-grid representation of the scattering wave function. The overset grid consists of a central grid and multiple dense atom-centered subgrids that allow the simultaneous spherical expansions of the wave function about multiple centers. Scattering boundary conditions are enforced by using a basis formed by the repeated application of the free-particle Green's function and potential Ĝ0+V ̂ on the overset grid in a Born-Arnoldi solution of the working equations. The theory is shown to be equivalent to a specific Padé approximant to the T matrix and has rapid convergence properties, in both the number of numerical basis functions employed and the number of partial waves employed in the spherical expansions. The method is demonstrated in calculations on methane and CF4 in the static-exchange approximation and compared in detail with calculations performed with the numerical Schwinger variational approach based on single-center expansions. An efficient procedure for operating with the free-particle Green's function and exchange operators (to which no approximation is made) is also described.

Spin-Multiplet Components and Energy Splittings by Multistate Density Functional Theory.

PubMed

Grofe, Adam; Chen, Xin; Liu, Wenjian; Gao, Jiali

2017-10-05

Kohn-Sham density functional theory has been tremendously successful in chemistry and physics. Yet, it is unable to describe the energy degeneracy of spin-multiplet components with any approximate functional. This work features two contributions. (1) We present a multistate density functional theory (MSDFT) to represent spin-multiplet components and to determine multiplet energies. MSDFT is a hybrid approach, taking advantage of both wave function theory and density functional theory. Thus, the wave functions, electron densities and energy density-functionals for ground and excited states and for different components are treated on the same footing. The method is illustrated on valence excitations of atoms and molecules. (2) Importantly, a key result is that for cases in which the high-spin components can be determined separately by Kohn-Sham density functional theory, the transition density functional in MSDFT (which describes electronic coupling) can be defined rigorously. The numerical results may be explored to design and optimize transition density functionals for configuration coupling in multiconfigurational DFT.

Observation of the Rabi oscillation of light driven by an atomic spin wave.

PubMed

Chen, L Q; Zhang, Guo-Wan; Bian, Cheng-Ling; Yuan, Chun-Hua; Ou, Z Y; Zhang, Weiping

2010-09-24

Coherent conversion between a Raman pump field and its Stokes field is observed in a Raman process with a strong atomic spin wave initially prepared by another Raman process operated in the stimulated emission regime. The oscillatory behavior resembles the Rabi oscillation in atomic population in a two-level atomic system driven by a strong light field. The Rabi-like oscillation frequency is found to be related to the strength of the prebuilt atomic spin wave. High conversion efficiency of 40% from the Raman pump field to the Stokes field is recorded and it is independent of the input Raman pump field. This process can act as a photon frequency multiplexer and may find wide applications in quantum information science.

Direct Calculation of the Scattering Amplitude Without Partial Wave Decomposition. III; Inclusion of Correlation Effects

NASA Technical Reports Server (NTRS)

Shertzer, Janine; Temkin, Aaron

2007-01-01

In the first two papers in this series, we developed a method for studying electron-hydrogen scattering that does not use partial wave analysis. We constructed an ansatz for the wave function in both the static and static exchange approximations and calculated the full scattering amplitude. Here we go beyond the static exchange approximation, and include correlation in the wave function via a modified polarized orbital. This correlation function provides a significant improvement over the static exchange approximation: the resultant elastic scattering amplitudes are in very good agreement with fully converged partial wave calculations for electron-hydrogen scattering. A fully variational modification of this approach is discussed in the conclusion of the article Popular summary of Direct calculation of the scattering amplitude without partial wave expansion. III ....." by J. Shertzer and A. Temkin. In this paper we continue the development of In this paper we continue the development of a new approach to the way in which researchers have traditionally used to calculate the scattering cross section of (low-energy) electrons from atoms. The basic mathematical problem is to solve the Schroedinger Equation (SE) corresponding the above physical process. Traditionally it was always the case that the SE was reduced to a sequence of one-dimensional (ordinary) differential equations - called partial waves which were solved and from the solutions "phase shifts" were extracted, from which the scattering cross section was calculated.

High-sensitivity rotation sensing with atom interferometers using Aharonov-Bohm effect

NASA Astrophysics Data System (ADS)

Özcan, Meriac

2006-02-01

In recent years there has been significant activity in research and development of high sensitivity accelerometers and gyroscopes using atom interferometers. In these devices, a fringe shift in the interference of atom de Broglie waves indicates the rotation rate of the interferometer relative to an inertial frame of reference. In both optical and atomic conventional Sagnac interferometers, the resultant phase difference due to rotation is independent of the wave velocity. However, we show that if an atom interforemeter is enclosed in a Faraday cage which is at some potential, the phase difference of the counter-propagating waves is proportional to the inverse square of the particle velocity and it is proportional to the applied potential. This is due to Aharonov-Bohm effect and it can be used to increase the rotation sensitivity of atom interferometers.

Charge exchange cross sections in slow collisions of Si3+ with Hydrogen atom

NASA Astrophysics Data System (ADS)

Joseph, Dwayne; Quashie, Edwin; Saha, Bidhan

2011-05-01

In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. Work supported by NSF CREST project (grant #0630370).

An electron of helium atom under a high-intensity laser field

NASA Astrophysics Data System (ADS)

Falaye, Babatunde James; Sun, Guo-Hua; Adepoju, Adenike Grace; Liman, Muhammed S.; Oyewumi, K. J.; Dong, Shi-Hai

2017-02-01

We scrutinize the behavior of eigenvalues of an electron in a helium (He) atom as it interacts with electric field directed along the z-axis and is exposed to linearly polarized intense laser field radiation. To achieve this, we freeze one electron of the He atom at its ionic ground state and the motion of the second electron in the ion core is treated via a more general case of screened Coulomb potential model. Using the Kramers-Henneberger (KH) unitary transformation, which is the semiclassical counterpart of the Block-Nordsieck transformation in the quantized field formalism, the squared vector potential that appears in the equation of motion is eliminated and the resultant equation is expressed in the KH frame. Within this frame, the resulting potential and the corresponding wave function are expanded in Fourier series and using Ehlotzky’s approximation, we obtain a laser-dressed potential to simulate intense laser field. By fitting the more general case of screened Coulomb potential model into the laser-dressed potential, and then expanding it in Taylor series up to O≤ft({{r}4},α 09\\right) , we obtain the solution (eigenvalues and wave function) of an electron in a He atom under the influence of external electric field and high-intensity laser field, within the framework of perturbation theory formalism. We found that the variation in frequency of laser radiation has no effect on the eigenvalues of a He electron for a particular electric field intensity directed along z-axis. Also, for a very strong external electric field and an infinitesimal screening parameter, the system is strongly bound. This work has potential application in the areas of atomic and molecular processes in external fields including interactions with strong fields and short pulses.

Impact of inelastic processes on the chaotic dynamics of a Bose-Einstein condensate trapped into a moving optical lattice

NASA Astrophysics Data System (ADS)

Tchatchueng, Sylvin; Siewe Siewe, Martin; Marie Moukam Kakmeni, François; Tchawoua, Clément

2017-03-01

We investigate the dynamics of a Bose-Einstein condensate with attractive two-body and repulsive three-body interactions between atoms trapped into a moving optical lattice and subjected to some inelastic processes (a linear atomic feeding and two dissipative terms related to dipolar relaxation and three-body recombination). We are interested in finding out how the nonconservative terms mentioned above act on the dynamical behaviour of the condensate, and how they can be used in the control of possible chaotic dynamics. Seeking the wave function of condensate on the form of Bloch waves, we notice that the real amplitude of the condensate is governed by an integro-differential equation. As theoretical tool of prediction of homoclinic and heteroclinic chaos, we use the Melnikov method, which provides two Melnikov functions related to homoclinic and heteroclinic bifurcations. Applying the Melnikov criterion, some regions of instability are plotted in the parameter space and reveal complex dynamics (solitonic stable solutions, weak and strong instabilities leading to collapse, growth-collapse cycles and finally to chaotic oscillations). It comes from some parameter space that coupling the optical intensity and parameters related to atomic feeding and atomic losses (dissipations) as control parameters can help to reduce or annihilate chaotic behaviours of the condensate. Moreover, the theoretical study reveals that there is a certain ratio between the atomic feeding parameter and the parameters related to the dissipation for the occurrence of chaotic oscillations in the dynamics of condensate. The theoretical predictions are verified by numerical simulations (Poincaré sections), and there is a certain reliability of our analytical treatment.

Chirped-Pulse Millimeter-Wave Spectroscopy of Rydberg-Rydberg Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prozument, Kirill; Colombo, Anthony P.; Zhou Yan

2011-09-30

Transitions between Rydberg states of Ca atoms, in a pulsed, supersonic atomic beam, are directly detected by chirped-pulse millimeter-wave spectroscopy. Broadband, high-resolution spectra with accurate relative intensities are recorded instantly. Free induction decay (FID) of atoms, polarized by the chirped pulse, at their Rydberg-Rydberg transition frequencies, is heterodyne detected, averaged in the time domain, and Fourier transformed into the frequency domain. Millimeter-wave transient nutations are observed, and the possibility of FID evolving to superradiance is discussed.

A quantum trampoline for ultra-cold atoms

NASA Astrophysics Data System (ADS)

Robert-de-Saint-Vincent, M.; Brantut, J.-P.; Bordé, Ch. J.; Aspect, A.; Bourdel, T.; Bouyer, P.

2010-01-01

We have observed the interferometric suspension of a free-falling Bose-Einstein condensate periodically submitted to multiple-order diffraction by a vertical 1D standing wave. This scheme permits simultaneously the compensation of gravity and coherent splitting/recombination of the matter waves. It results in high-contrast interference in the number of atoms detected at constant height. For long suspension times, multiple-wave interference is revealed through a sharpening of the fringes. We characterize our atom interferometer and use it to measure the acceleration of gravity.

Atomic adsorption on pristine graphene along the Periodic Table of Elements - From PBE to non-local functionals

NASA Astrophysics Data System (ADS)

Pašti, Igor A.; Jovanović, Aleksandar; Dobrota, Ana S.; Mentus, Slavko V.; Johansson, Börje; Skorodumova, Natalia V.

2018-04-01

The understanding of atomic adsorption on graphene is of high importance for many advanced technologies. Here we present a complete database of the atomic adsorption energies for the elements of the Periodic Table up to the atomic number 86 (excluding lanthanides) on pristine graphene. The energies have been calculated using the projector augmented wave (PAW) method with PBE, long-range dispersion interaction corrected PBE (PBE+D2, PBE+D3) as well as non-local vdW-DF2 approach. The inclusion of dispersion interactions leads to an exothermic adsorption for all the investigated elements. Dispersion interactions are found to be of particular importance for the adsorption of low atomic weight earth alkaline metals, coinage and s-metals (11th and 12th groups), high atomic weight p-elements and noble gases. We discuss the observed adsorption trends along the groups and rows of the Periodic Table as well some computational aspects of modelling atomic adsorption on graphene.

Revisiting the adsorption of copper-phthalocyanine on Au(111) including van der Waals corrections.

PubMed

Lüder, Johann; Eriksson, Olle; Sanyal, Biplab; Brena, Barbara

2014-03-28

We have studied the adsorption of copper-phthalocyanine on Au(111) by means of van der Waals corrected density functional theory using the Tkatchenko-Scheffler method. We have compared the element and site resolved adsorption distances to recent experimental normal-incident X-ray standing wave measurements. The measured adsorption distances could be reproduced within a deviation of 1% for the Cu atom, 1% for the C atoms, and 2% for the N atoms. The molecule was found to have a magnetic moment of 1 μB distributed over the Cu and the N atoms of the pyrrole ring. Simulated scanning tunnel microscopy images based on the total and on the spin-resolved differential charge densities are provided for bias voltages of -1.45 and 1.45 eV.

Coherent forward broadening in cold atom clouds

NASA Astrophysics Data System (ADS)

Sutherland, R. T.; Robicheaux, F.

2016-02-01

It is shown that homogeneous line-broadening in a diffuse cold atom cloud is proportional to the resonant optical depth of the cloud. Furthermore, it is demonstrated how the strong directionality of the coherent interactions causes the cloud's spectra to depend strongly on its shape, even when the cloud is held at constant densities. These two numerical observations can be predicted analytically by extending the single-photon wave-function model. Lastly, elongating a cloud along the line of laser propagation causes the excitation probability distribution to deviate from the exponential decay predicted by the Beer-Lambert law to the extent where the atoms at the back of the cloud are more excited than the atoms at the front. These calculations are conducted at the low densities relevant to recent experiments.

Atomic photoionization in a strong magnetic field

NASA Astrophysics Data System (ADS)

Greene, C. H.

1983-10-01

The photoionization of hydrogen atoms in a strong magnetic field is formulated as a multichannel problem by representing the asymptotic electron-wave function in cylindrical coordinates. Departures from cylindrical symmetry close to the nucleus are incorporated by an R-matrix treatment at short range, which then merges with standard quantum-defect procedures. The R-matrix calculation utilizes the eigenchannel approach, recast in noniterative form. At the field strength treated here, B = 4.7 x 10 to the 9th G, the photoionization cross section displays narrow 'autoionizing' resonances near the excited Landau thresholds.

Experimental Observation of Two-Dimensional Anderson Localization with the Atomic Kicked Rotor.

PubMed

Manai, Isam; Clément, Jean-François; Chicireanu, Radu; Hainaut, Clément; Garreau, Jean Claude; Szriftgiser, Pascal; Delande, Dominique

2015-12-11

Dimension 2 is expected to be the lower critical dimension for Anderson localization in a time-reversal-invariant disordered quantum system. Using an atomic quasiperiodic kicked rotor-equivalent to a two-dimensional Anderson-like model-we experimentally study Anderson localization in dimension 2 and we observe localized wave function dynamics. We also show that the localization length depends exponentially on the disorder strength and anisotropy and is in quantitative agreement with the predictions of the self-consistent theory for the 2D Anderson localization.

Round Table Workshop on the Frontiers of Condensed Matter Physics Held in Broomcroft Hall, Manchester on 24-25 September 1990

DTIC Science & Technology

1990-12-01

Jaynes - Cummings model (describing a two-level atom in a radiant cavity), in which the interaction between atom and radiation field is non- linearly...dependent on the field intensity [14]. It is interesting to notice that such an application was fostered by the observation that the Jaynes - Cummings model in...ai i an anilation operator of the radition field and .o is a spin operator of an electron wave function, can be approximated by the product <a,,> ɜ"V

Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

NASA Astrophysics Data System (ADS)

Borges, L. H. C.; Barone, F. A.

2016-02-01

Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schrödinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector.

The divine clockwork: Bohr's correspondence principle and Nelson's stochastic mechanics for the atomic elliptic state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durran, Richard; Neate, Andrew; Truman, Aubrey

2008-03-15

We consider the Bohr correspondence limit of the Schroedinger wave function for an atomic elliptic state. We analyze this limit in the context of Nelson's stochastic mechanics, exposing an underlying deterministic dynamical system in which trajectories converge to Keplerian motion on an ellipse. This solves the long standing problem of obtaining Kepler's laws of planetary motion in a quantum mechanical setting. In this quantum mechanical setting, local mild instabilities occur in the Keplerian orbit for eccentricities greater than (1/{radical}(2)) which do not occur classically.

Wigner molecules: the strong-correlation limit of the three-electron harmonium.

PubMed

Cioslowski, Jerzy; Pernal, Katarzyna

2006-08-14

At the strong-correlation limit, electronic states of the three-electron harmonium atom are described by asymptotically exact wave functions given by products of distinct Slater determinants and a common Gaussian factor that involves interelectron distances and the center-of-mass position. The Slater determinants specify the angular dependence and the permutational symmetry of the wave functions. As the confinement strength becomes infinitesimally small, the states of different spin multiplicities become degenerate, their limiting energy reflecting harmonic vibrations of the electrons about their equilibrium positions. The corresponding electron densities are given by products of angular factors and a Gaussian function centered at the radius proportional to the interelectron distance at equilibrium. Thanks to the availability of both the energy and the electron density, the strong-correlation limit of the three-electron harmonium is well suited for testing of density functionals.

Liquid?solid helium interface: some conceptual questions

NASA Astrophysics Data System (ADS)

Leggett, A. J.

2003-12-01

I raise, and discuss qualitatively, some conceptual issues concerning the interface between the crystalline solid and superfluid liquid phases of 4He emphasizing, in particular, the fact that the ground-state wave functions of the two phases are prima facie qualitatively quite different, in that the superfluid liquid phase possesses off-diagonal long-range order (ODLRO), while the crystalline solid does not. The fact that the statics and dynamics of the interface do not appear to be particularly sensitive to the presence of ODLRO in the liquid is tentatively explained by the fact that because of a subtlety associated with the Bose statistics obeyed by the atoms, the solid and liquid wave functions are not locally very different.

Two-body loss rates for reactive collisions of cold atoms

NASA Astrophysics Data System (ADS)

Cop, C.; Walser, R.

2018-01-01

We present an effective two-channel model for reactive collisions of cold atoms. It augments elastic molecular channels with an irreversible, inelastic loss channel. Scattering is studied with the distorted-wave Born approximation and yields general expressions for angular momentum resolved cross sections as well as two-body loss rates. Explicit expressions are obtained for piecewise constant potentials. A pole expansion reveals simple universal shape functions for cross sections and two-body loss rates in agreement with the Wigner threshold laws. This is applied to collisions of metastable 20Ne and 21Ne atoms, which decay primarily through exothermic Penning or associative ionization processes. From a numerical solution of the multichannel Schrödinger equation using the best currently available molecular potentials, we have obtained synthetic scattering data. Using the two-body loss shape functions derived in this paper, we can match these scattering data very well.

Magnetism and exchange interaction of small rare-earth clusters; Tb as a representative

PubMed Central

Peters, Lars; Ghosh, Saurabh; Sanyal, Biplab; van Dijk, Chris; Bowlan, John; de Heer, Walt; Delin, Anna; Di Marco, Igor; Eriksson, Olle; Katsnelson, Mikhail I.; Johansson, Börje; Kirilyuk, Andrei

2016-01-01

Here we follow, both experimentally and theoretically, the development of magnetism in Tb clusters from the atomic limit, adding one atom at a time. The exchange interaction is, surprisingly, observed to drastically increase compared to that of bulk, and to exhibit irregular oscillations as a function of the interatomic distance. From electronic structure theory we find that the theoretical magnetic moments oscillate with cluster size in exact agreement with experimental data. Unlike the bulk, the oscillation is not caused by the RKKY mechanism. Instead, the inter-atomic exchange is shown to be driven by a competition between wave-function overlap of the 5d shell and the on-site exchange interaction, which leads to a competition between ferromagnetic double-exchange and antiferromagnetic super-exchange. This understanding opens up new ways to tune the magnetic properties of rare-earth based magnets with nano-sized building blocks. PMID:26795239

Fluorine and sulfur simultaneously co-doped suspended graphene

NASA Astrophysics Data System (ADS)

Struzzi, C.; Sezen, H.; Amati, M.; Gregoratti, L.; Reckinger, N.; Colomer, J.-F.; Snyders, R.; Bittencourt, C.; Scardamaglia, M.

2017-11-01

Suspended graphene flakes are exposed simultaneously to fluorine and sulfur ions produced by the μ-wave plasma discharge of the SF6 precursor gas. The microscopic and spectroscopic analyses, performed by Raman spectroscopy, scanning electron microscopy and photoelectron spectromicroscopy, show the homogeneity in functionalization yield over the graphene flakes with F and S atoms covalently bonded to the carbon lattice. This promising surface shows potential for several applications ranging from biomolecule immobilization to lithium battery and hydrogen storage devices. The present co-doping process is an optimal strategy to engineer the graphene surface with a concurrent hydrophobic character, thanks to the fluorine atoms, and a high affinity with metal nanoparticles due to the presence of sulfur atoms.

Dynamics of entanglement between two atomic samples with spontaneous scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Lisi, Antonio; De Siena, Silvio; Illuminati, Fabrizio

2004-07-01

We investigate the effects of spontaneous scattering on the evolution of entanglement of two atomic samples, probed by phase-shift measurements on optical beams interacting with both samples. We develop a formalism of conditional quantum evolutions and present a wave function analysis implemented in numerical simulations of the state vector dynamics. This method allows us to track the evolution of entanglement and to compare it with the predictions obtained when spontaneous scattering is neglected. We provide numerical evidence that the interferometric scheme to entangle atomic samples is only marginally affected by the presence of spontaneous scattering and should thus be robustmore » even in more realistic situations.« less

Matter-wave diffraction approaching limits predicted by Feynman path integrals for multipath interference

NASA Astrophysics Data System (ADS)

Barnea, A. Ronny; Cheshnovsky, Ori; Even, Uzi

2018-02-01

Interference experiments have been paramount in our understanding of quantum mechanics and are frequently the basis of testing the superposition principle in the framework of quantum theory. In recent years, several studies have challenged the nature of wave-function interference from the perspective of Born's rule—namely, the manifestation of so-called high-order interference terms in a superposition generated by diffraction of the wave functions. Here we present an experimental test of multipath interference in the diffraction of metastable helium atoms, with large-number counting statistics, comparable to photon-based experiments. We use a variation of the original triple-slit experiment and accurate single-event counting techniques to provide a new experimental bound of 2.9 ×10-5 on the statistical deviation from the commonly approximated null third-order interference term in Born's rule for matter waves. Our value is on the order of the maximal contribution predicted for multipath trajectories by Feynman path integrals.

Nonautonomous characteristics of the breathers and rogue waves for a amplifier nonlinear Schrödinger Maxwell-Bloch system

NASA Astrophysics Data System (ADS)

Wang, Lei; Li, Xiao; Zhang, Lu Lu; Li, Min; Qi, Feng-Hua

2015-09-01

Under investigation in this paper is a amplifier nonlinear Schrödinger Maxwell-Bloch (NLS-MB) system which describes the propagation of optical pulses in an inhomogeneous erbium doped fiber. Nonautonomous breather and rogue wave (RW) solutions of the amplifier NLS-MB system are constructed via the modified Darboux transformation with the inhomogeneous parameters. By suitably choosing the dispersion coefficient function, several types of inhomogeneous nonlinear waves are obtained in: (1) periodically fluctuating dispersion profile; (2) exponentially increasing (or decreasing) dispersion profile; and (3) linearly decreasing (increasing) dispersion profile. The nonautonomous characteristics of the breathers and RWs are graphically investigated, including the breather accelerating and decelerating motions, boomerang breather, breather compression, breather evolution, periodic RW, boomerang RW and stationary RW. Such novel patterns as the periodic breathers and rogue-wave fission of the amplifier NLS-MB system are exhibited by properly adjusting the group velocity dispersion function and interaction parameter between silica and doped atoms.

Theory of electron-impact ionization of atoms

NASA Astrophysics Data System (ADS)

Kadyrov, A. S.; Mukhamedzhanov, A. M.; Stelbovics, A. T.; Bray, I.

2004-12-01

The existing formulations of electron-impact ionization of a hydrogenic target suffer from a number of formal problems including an ambiguous and phase-divergent definition of the ionization amplitude. An alternative formulation of the theory is given. An integral representation for the ionization amplitude which is free of ambiguity and divergence problems is derived and is shown to have four alternative, but equivalent, forms well suited for practical calculations. The extension to amplitudes of all possible scattering processes taking place in an arbitrary three-body system follows. A well-defined conventional post form of the breakup amplitude valid for arbitrary potentials including the long-range Coulomb interaction is given. Practical approaches are based on partial-wave expansions, so the formulation is also recast in terms of partial waves and partial-wave expansions of the asymptotic wave functions are presented. In particular, expansions of the asymptotic forms of the total scattering wave function, developed from both the initial and the final state, for electron-impact ionization of hydrogen are given. Finally, the utility of the present formulation is demonstrated on some well-known model problems.

Periodic boundary conditions for QM/MM calculations: Ewald summation for extended Gaussian basis sets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holden, Zachary C.; Richard, Ryan M.; Herbert, John M., E-mail: herbert@chemistry.ohio-state.edu

2013-12-28

An implementation of Ewald summation for use in mixed quantum mechanics/molecular mechanics (QM/MM) calculations is presented, which builds upon previous work by others that was limited to semi-empirical electronic structure for the QM region. Unlike previous work, our implementation describes the wave function's periodic images using “ChElPG” atomic charges, which are determined by fitting to the QM electrostatic potential evaluated on a real-space grid. This implementation is stable even for large Gaussian basis sets with diffuse exponents, and is thus appropriate when the QM region is described by a correlated wave function. Derivatives of the ChElPG charges with respect tomore » the QM density matrix are a potentially serious bottleneck in this approach, so we introduce a ChElPG algorithm based on atom-centered Lebedev grids. The ChElPG charges thus obtained exhibit good rotational invariance even for sparse grids, enabling significant cost savings. Detailed analysis of the optimal choice of user-selected Ewald parameters, as well as timing breakdowns, is presented.« less

Towards laser spectroscopy of the proton-halo candidate boron-8

NASA Astrophysics Data System (ADS)

Maaß, Bernhard; Müller, Peter; Nörtershäuser, Wilfried; Clark, Jason; Gorges, Christian; Kaufmann, Simon; König, Kristian; Krämer, Jörg; Levand, Anthony; Orford, Rodney; Sánchez, Rodolfo; Savard, Guy; Sommer, Felix

2017-11-01

We propose to determine the nuclear charge radius of 8B by high-resolution laser spectroscopy. 8B (t 1/2 = 770 ms) is perhaps the best candidate of a nucleus exhibiting an extended proton wave-function or "one-proton-halo" in a more descriptive picture. Laser spectroscopic measurements of the isotope shift will be used to probe the change in nuclear charge radius along the three boron isotopes 8B, 10B and 11B. The change in nuclear charge radius directly correlates with the extent of the proton wave function. In-flight production and preparation of sufficient yields of 8B ions at low energies is provided by the Argonne Tandem Linac Accelerator System (ATLAS) at Argonne National Laboratory (ANL) in Chicago, IL, USA. Subsequently, the ions will be guided through a charge exchange cell for neutralization and the fluorescence signal of the atoms which interact with the resonant laser light will be detected. The charge radius can then be extracted from the measured isotope shift by employing highly accurate atomic theory calculations of this five-electron system which are carried out presently.

Highly Efficient Wave-Front Reshaping of Surface Waves with Dielectric Metawalls

NASA Astrophysics Data System (ADS)

Dong, Shaohua; Zhang, Yu; Guo, Huijie; Duan, Jingwen; Guan, Fuxin; He, Qiong; Zhao, Haibin; Zhou, Lei; Sun, Shulin

2018-01-01

Controlling the wave fronts of surface waves (including surface-plamon polaritons and their equivalent counterparts) at will is highly important in photonics research, but the available mechanisms suffer from the issues of low efficiency, bulky size, and/or limited functionalities. Inspired by recent studies of metasurfaces that can freely control the wave fronts of propagating waves, we propose to use metawalls placed on a plasmonic surface to efficiently reshape the wave fronts of incident surface waves (SWs). Here, the metawall is constructed by specifically designed meta-atoms that can reflect SWs with desired phases and nearly unit amplitudes. As a proof of concept, we design and fabricate a metawall in the microwave regime (around 12 GHz) that can anomalously reflect the SWs following the generalized Snell's law with high efficiency (approximately 70%). Our results, in excellent agreement with full-wave simulations, provide an alternative yet efficient way to control the wave fronts of SWs in different frequency domains. We finally employ full-wave simulations to demonstrate a surface-plasmon-polariton focusing effect at telecom wavelength based on our scheme.

One-dimensional Coulomb problem in Dirac materials

NASA Astrophysics Data System (ADS)

Downing, C. A.; Portnoi, M. E.

2014-11-01

We investigate the one-dimensional Coulomb potential with application to a class of quasirelativistic systems, so-called Dirac-Weyl materials, described by matrix Hamiltonians. We obtain the exact solution of the shifted and truncated Coulomb problems, with the wave functions expressed in terms of special functions (namely, Whittaker functions), while the energy spectrum must be determined via solutions to transcendental equations. Most notably, there are critical band gaps below which certain low-lying quantum states are missing in a manifestation of atomic collapse.

ELSEPA—Dirac partial-wave calculation of elastic scattering of electrons and positrons by atoms, positive ions and molecules

NASA Astrophysics Data System (ADS)

Salvat, Francesc; Jablonski, Aleksander; Powell, Cedric J.

2005-01-01

The FORTRAN 77 code system ELSEPA for the calculation of elastic scattering of electrons and positrons by atoms, positive ions and molecules is presented. These codes perform relativistic (Dirac) partial-wave calculations for scattering by a local central interaction potential V(r). For atoms and ions, the static-field approximation is adopted, with the potential set equal to the electrostatic interaction energy between the projectile and the target, plus an approximate local exchange interaction when the projectile is an electron. For projectiles with kinetic energies up to 10 keV, the potential may optionally include a semiempirical correlation-polarization potential to describe the effect of the target charge polarizability. Also, for projectiles with energies less than 1 MeV, an imaginary absorptive potential can be introduced to account for the depletion of the projectile wave function caused by open inelastic channels. Molecular cross sections are calculated by means of a single-scattering independent-atom approximation in which the electron density of a bound atom is approximated by that of the free neutral atom. Elastic scattering by individual atoms in solids is described by means of a muffin-tin model potential. Partial-wave calculations are feasible on modest personal computers for energies up to about 5 MeV. The ELSEPA code also implements approximate factorization methods that allow the fast calculation of elastic cross sections for much higher energies. The interaction model adopted in the calculations is defined by the user by combining the different options offered by the code. The nuclear charge distribution can be selected among four analytical models (point nucleus, uniformly charged sphere, Fermi's distribution and Helm's uniform-uniform distribution). The atomic electron density is handled in numerical form. The distribution package includes data files with electronic densities of neutral atoms of the elements hydrogen to lawrencium ( Z=1-103) obtained from multiconfiguration Dirac-Fock self-consistent calculations. For comparison purposes, three simple analytical approximations to the electron density of neutral atoms (corresponding to the Thomas-Fermi, the Thomas-Fermi-Dirac and the Dirac-Hartree-Fock-Slater models) are also included. For calculations of elastic scattering by ions, the electron density should be provided by the user. The exchange potential for electron scattering can be selected among three different analytical approximations (Thomas-Fermi, Furness-McCarthy, Riley-Truhlar). The offered options for the correlation-polarization potential are based on the empirical Buckingham potential. The imaginary absorption potential is calculated from the local-density approximation proposed by Salvat [Phys. Rev. A 68 (2003) 012708]. Program summaryTitle of program:ELSEPA Catalogue identifier: ADUS Program summary URL:http://cpc.cs.qub.ac.uk/cpc/summaries/ADUS Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland License provisions: none Computer for which the program is designed and others in which it is operable: Any computer with a FORTRAN 77 compiler Operating systems under which the program has been tested: Windows XP, Windows 2000, Debian GNU/Linux 3.0r0 (sarge) Compilers:Compaq Visual Fortran v6.5 (Windows); GNU FORTRAN, g77 (Windows and Linux) Programming language used: FORTRAN 77 No. of bits in a word: 32 Memory required to execute with typical data: 0.6 Mb No. of lines in distributed program, including test data, etc.:135 489 No. of bytes in distributed program, including test data, etc.: 1 280 006 Distribution format: tar.gz Keywords: Dirac partial-wave analysis, electron elastic scattering, positron elastic scattering, differential cross sections, momentum transfer cross sections, transport cross sections, scattering amplitudes, spin polarization, scattering by complex potentials, high-energy atomic screening functions Nature of the physical problem: The code calculates differential cross sections, total cross sections and transport cross sections for single elastic scattering of electrons and positrons by neutral atoms, positive ions and randomly oriented molecules. For projectiles with kinetic energies less than about 5 MeV, the programs can also compute scattering amplitudes and spin polarization functions. Method of solution: The effective interaction between the projectile and a target atom is represented by a local central potential that can optionally include an imaginary (absorptive) part to account approximately for the coupling with inelastic channels. For projectiles with kinetic energy less that about 5 MeV, the code performs a conventional relativistic Dirac partial-wave analysis. For higher kinetic energies, where the convergence of the partial-wave series is too slow, approximate factorization methods are used. Restrictions on the complexity of the program: The calculations are based on the static-field approximation. The optional correlation-polarization and inelastic absorption corrections are obtained from approximate, semiempirical models. Calculations for molecules are based on a single-scattering independent-atom approximation. To ensure accuracy of the results for scattering by ions, the electron density of the ion must be supplied by the user. Typical running time: on a 2.8 GHz Pentium 4, the calculation of elastic scattering by atoms and ions takes between a few seconds and about two minutes, depending on the atomic number of the target, the adopted potential model and the kinetic energy of the projectile. Unusual features of the program: The program calculates elastic cross sections for electrons and positrons with kinetic energies in a wide range, from a few tens of eV up to about 1 GeV. Calculations can be performed for neutral atoms of all elements, from hydrogen to lawrencium ( Z=1-103), ions and simple molecules. Commercial products are identified to specify the calculational procedures. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, the University of Barcelona or the Polish Academy of Sciences, nor does it imply that the products are necessarily the best available for the purpose.

Tunable microwave metasurfaces for high-performance operations: dispersion compensation and dynamical switch

PubMed Central

Xu, He-Xiu; Tang, Shiwei; Ma, Shaojie; Luo, Weijie; Cai, Tong; Sun, Shulin; He, Qiong; Zhou, Lei

2016-01-01

Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices’ performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode. We experimentally demonstrate two effects utilizing our scheme. First, we show that a tunable gradient metasurface exhibits single-mode high-efficiency operation within a wide frequency band, while its passive counterpart only works at a single frequency but exhibits deteriorated performances at other frequencies. Second, we demonstrate that the functionality of our metasurface can be dynamically switched from a specular reflector to a surface-wave convertor. Our approach paves the road to achieve dispersion-corrected and switchable manipulations of electromagnetic waves. PMID:27901088

Tunable microwave metasurfaces for high-performance operations: dispersion compensation and dynamical switch.

PubMed

Xu, He-Xiu; Tang, Shiwei; Ma, Shaojie; Luo, Weijie; Cai, Tong; Sun, Shulin; He, Qiong; Zhou, Lei

2016-11-30

Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices' performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode. We experimentally demonstrate two effects utilizing our scheme. First, we show that a tunable gradient metasurface exhibits single-mode high-efficiency operation within a wide frequency band, while its passive counterpart only works at a single frequency but exhibits deteriorated performances at other frequencies. Second, we demonstrate that the functionality of our metasurface can be dynamically switched from a specular reflector to a surface-wave convertor. Our approach paves the road to achieve dispersion-corrected and switchable manipulations of electromagnetic waves.

Tunable microwave metasurfaces for high-performance operations: dispersion compensation and dynamical switch

NASA Astrophysics Data System (ADS)

Xu, He-Xiu; Tang, Shiwei; Ma, Shaojie; Luo, Weijie; Cai, Tong; Sun, Shulin; He, Qiong; Zhou, Lei

2016-11-01

Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices’ performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode. We experimentally demonstrate two effects utilizing our scheme. First, we show that a tunable gradient metasurface exhibits single-mode high-efficiency operation within a wide frequency band, while its passive counterpart only works at a single frequency but exhibits deteriorated performances at other frequencies. Second, we demonstrate that the functionality of our metasurface can be dynamically switched from a specular reflector to a surface-wave convertor. Our approach paves the road to achieve dispersion-corrected and switchable manipulations of electromagnetic waves.

Basis convergence of range-separated density-functional theory.

PubMed

Franck, Odile; Mussard, Bastien; Luppi, Eleonora; Toulouse, Julien

2015-02-21

Range-separated density-functional theory (DFT) is an alternative approach to Kohn-Sham density-functional theory. The strategy of range-separated density-functional theory consists in separating the Coulomb electron-electron interaction into long-range and short-range components and treating the long-range part by an explicit many-body wave-function method and the short-range part by a density-functional approximation. Among the advantages of using many-body methods for the long-range part of the electron-electron interaction is that they are much less sensitive to the one-electron atomic basis compared to the case of the standard Coulomb interaction. Here, we provide a detailed study of the basis convergence of range-separated density-functional theory. We study the convergence of the partial-wave expansion of the long-range wave function near the electron-electron coalescence. We show that the rate of convergence is exponential with respect to the maximal angular momentum L for the long-range wave function, whereas it is polynomial for the case of the Coulomb interaction. We also study the convergence of the long-range second-order Møller-Plesset correlation energy of four systems (He, Ne, N2, and H2O) with cardinal number X of the Dunning basis sets cc - p(C)V XZ and find that the error in the correlation energy is best fitted by an exponential in X. This leads us to propose a three-point complete-basis-set extrapolation scheme for range-separated density-functional theory based on an exponential formula.

Total Born approximation cross sections for single electron loss by atoms and ions colliding with atoms

NASA Technical Reports Server (NTRS)

Rule, D. W.

1977-01-01

The first born approximation (FBA) is applied to the calculation of single electron loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions were used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors were used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with respect to the projectile nuclear charge was explored in the case of hydrogen-like ions. Scaling of the cross section with respect to the target nuclear charge for electron loss by Fe (+25) in collision with neutral atoms ranging from H to Fe is also examined. These results were compared to those of the binary encounter approximation and to the FBA for the case of ionization by completely stripped target ions.

Realization of a twin beam source based on four-wave mixing in Cesium

NASA Astrophysics Data System (ADS)

Adenier, G.; Calonico, D.; Micalizio, S.; Samantaray, N.; Degiovanni, I. P.; Berchera, I. Ruo

2016-05-01

Four-wave mixing (4WM) is a known source of intense non-classical twin beams. It can be generated when an intense laser beam (the pump) and a weak laser beam (the seed) overlap in a χ(3) medium (here Cesium vapor), with frequencies close to resonance with atomic transitions. The twin beams generated by 4WM have frequencies naturally close to atomic transitions, and can be intense (gain ≫1) even in the CW pump regime, which is not the case for PDC χ(2) phenomenon in nonlinear crystals. So, 4WM is well suited for atom-light interaction and atom-based quantum-protocols. Here, we present the first realization of a source of 4-wave mixing exploiting D2 line of Cesium atoms.

Solving the Schroedinger equation for helium atom and its isoelectronic ions with the free iterative complement interaction (ICI) method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakashima, Hiroyuki; Nakatsuji, Hiroshi

2007-12-14

The Schroedinger equation was solved very accurately for helium atom and its isoelectronic ions (Z=1-10) with the free iterative complement interaction (ICI) method followed by the variational principle. We obtained highly accurate wave functions and energies of helium atom and its isoelectronic ions. For helium, the calculated energy was -2.903 724 377 034 119 598 311 159 245 194 404 446 696 905 37 a.u., correct over 40 digit accuracy, and for H{sup -}, it was -0.527 751 016 544 377 196 590 814 566 747 511 383 045 02 a.u. These results prove numerically that with the free ICImore » method, we can calculate the solutions of the Schroedinger equation as accurately as one desires. We examined several types of scaling function g and initial function {psi}{sub 0} of the free ICI method. The performance was good when logarithm functions were used in the initial function because the logarithm function is physically essential for three-particle collision area. The best performance was obtained when we introduce a new logarithm function containing not only r{sub 1} and r{sub 2} but also r{sub 12} in the same logarithm function.« less

Inertial quantum sensors using light and matter

NASA Astrophysics Data System (ADS)

Barrett, B.; Bertoldi, A.; Bouyer, P.

2016-05-01

The past few decades have seen dramatic progress in our ability to manipulate and coherently control matter-waves. Although the duality between particles and waves has been well tested since de Broglie introduced the matter-wave analog of the optical wavelength in 1924, manipulating atoms with a level of coherence that enables one to use these properties for precision measurements has only become possible with our ability to produce atomic samples exhibiting temperatures of only a few millionths of a degree above absolute zero. Since the initial experiments a few decades ago, the field of atom optics has developed in many ways, with both fundamental and applied significance. The exquisite control of matter waves offers the prospect of a new generation of force sensors exhibiting unprecedented sensitivity and accuracy, for applications from navigation and geophysics to tests of general relativity. Thanks to the latest developments in this field, the first commercial products using this quantum technology are now available. In the future, our ability to create large coherent ensembles of atoms will allow us an even more precise control of the matter-wave and the ability to create highly entangled states for non-classical atom interferometry.

Prototyping method for Bragg-type atom interferometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benton, Brandon; Krygier, Michael; Heward, Jeffrey

2011-10-15

We present a method for rapid modeling of new Bragg ultracold atom-interferometer (AI) designs useful for assessing the performance of such interferometers. The method simulates the overall effect on the condensate wave function in a given AI design using two separate elements. These are (1) modeling the effect of a Bragg pulse on the wave function and (2) approximating the evolution of the wave function during the intervals between the pulses. The actual sequence of these pulses and intervals is then followed to determine the approximate final wave function from which the interference pattern can be calculated. The exact evolutionmore » between pulses is assumed to be governed by the Gross-Pitaevskii (GP) equation whose solution is approximated using a Lagrangian variational method to facilitate rapid estimation of performance. The method presented here is an extension of an earlier one that was used to analyze the results of an experiment [J. E. Simsarian et al., Phys. Rev. Lett. 85, 2040 (2000)], where the phase of a Bose-Einstein condensate was measured using a Mach-Zehnder-type Bragg AI. We have developed both 1D and 3D versions of this method and we have determined their validity by comparing their predicted interference patterns with those obtained by numerical integration of the 1D GP equation and with the results of the above experiment. We find excellent agreement between the 1D interference patterns predicted by this method and those found by the GP equation. We show that we can reproduce all of the results of that experiment without recourse to an ad hoc velocity-kick correction needed by the earlier method, including some experimental results that the earlier model did not predict. We also found that this method provides estimates of 1D interference patterns at least four orders-of-magnitude faster than direct numerical solution of the 1D GP equation.« less

Integrated coherent matter wave circuits

DOE PAGES

Ryu, C.; Boshier, M. G.

2015-09-21

An integrated coherent matter wave circuit is a single device, analogous to an integrated optical circuit, in which coherent de Broglie waves are created and then launched into waveguides where they can be switched, divided, recombined, and detected as they propagate. Applications of such circuits include guided atom interferometers, atomtronic circuits, and precisely controlled delivery of atoms. We report experiments demonstrating integrated circuits for guided coherent matter waves. The circuit elements are created with the painted potential technique, a form of time-averaged optical dipole potential in which a rapidly moving, tightly focused laser beam exerts forces on atoms through theirmore » electric polarizability. Moreover, the source of coherent matter waves is a Bose–Einstein condensate (BEC). Finally, we launch BECs into painted waveguides that guide them around bends and form switches, phase coherent beamsplitters, and closed circuits. These are the basic elements that are needed to engineer arbitrarily complex matter wave circuitry.« less

Denoising in digital speckle pattern interferometry using wave atoms.

PubMed

Federico, Alejandro; Kaufmann, Guillermo H

2007-05-15

We present an effective method for speckle noise removal in digital speckle pattern interferometry, which is based on a wave-atom thresholding technique. Wave atoms are a variant of 2D wavelet packets with a parabolic scaling relation and improve the sparse representation of fringe patterns when compared with traditional expansions. The performance of the denoising method is analyzed by using computer-simulated fringes, and the results are compared with those produced by wavelet and curvelet thresholding techniques. An application of the proposed method to reduce speckle noise in experimental data is also presented.

Excitation of the hydrogen atom by fast-electron impact in the presence of a laser field

NASA Astrophysics Data System (ADS)

Bhattacharya, Manabesh; Sinha, C.; Sil, N. C.

1991-08-01

An approach has been developed to study the excitation of a ground-state H atom to the n=2 level under the simultaneous action of fast-electron impact and a monochromatic, linearly polarized, homogeneous laser beam. The laser frequency is assumed to be low (soft-photon limit) so that a stationary-state perturbation theory can be applied as is done in the adiabatic theory. An elegant method has been developed in the present work to construct the dressed excited-state wave functions of the H atom using first-order perturbation theory in the parabolic coordinate representation. By virtue of this method, the problem arising due to the degeneracy of the excited states of the H atom has been successfully overcome. The main advantage of the present approach is that the dressed wave function has been obtained in terms of a finite number of Laguerre polynomials instead of an infinite summation occurring in the usual perturbative treatment. The amplitude for direct excitation (without exchange) has been obtained in closed form. Numerical results for differential cross sections are presented for individual excitations to different Stark manifolds as well as for excitations to the n=2 level at high energies (100 and 200 eV) and for field directions both parallel and perpendicular to the incident electron momentum. Extension to a higher order of perturbation is also possible in the present approach for the construction of the dressed states, and the electron-exchange effect can also be taken into account without any further approximation.

Hybrid Surface Acoustic Wave- Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films

PubMed Central

Choi, Kyung Hyun; Kim, Hyun Bum; Ali, Kamran; Sajid, Memoon; Uddin Siddiqui, Ghayas; Chang, Dong Eui; Kim, Hyung Chan; Ko, Jeong Beom; Dang, Hyun Woo; Doh, Yang Hoi

2015-01-01

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PEDOT:PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films’ characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics. PMID:26478189

Hybrid Surface Acoustic Wave- Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films

NASA Astrophysics Data System (ADS)

Choi, Kyung Hyun; Kim, Hyun Bum; Ali, Kamran; Sajid, Memoon; Uddin Siddiqui, Ghayas; Chang, Dong Eui; Kim, Hyung Chan; Ko, Jeong Beom; Dang, Hyun Woo; Doh, Yang Hoi

2015-10-01

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PEDOT:PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films’ characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics.

Hybrid Surface Acoustic Wave-Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films.

PubMed

Choi, Kyung Hyun; Kim, Hyun Bum; Ali, Kamran; Sajid, Memoon; Uddin Siddiqui, Ghayas; Chang, Dong Eui; Kim, Hyung Chan; Ko, Jeong Beom; Dang, Hyun Woo; Doh, Yang Hoi

2015-10-19

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate ( PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films' characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics.

A universal quantum information processor for scalable quantum communication and networks

PubMed Central

Yang, Xihua; Xue, Bolin; Zhang, Junxiang; Zhu, Shiyao

2014-01-01

Entanglement provides an essential resource for quantum computation, quantum communication, and quantum networks. How to conveniently and efficiently realize the generation, distribution, storage, retrieval, and control of multipartite entanglement is the basic requirement for realistic quantum information processing. Here, we present a theoretical proposal to efficiently and conveniently achieve a universal quantum information processor (QIP) via atomic coherence in an atomic ensemble. The atomic coherence, produced through electromagnetically induced transparency (EIT) in the Λ-type configuration, acts as the QIP and has full functions of quantum beam splitter, quantum frequency converter, quantum entangler, and quantum repeater. By employing EIT-based nondegenerate four-wave mixing processes, the generation, exchange, distribution, and manipulation of light-light, atom-light, and atom-atom multipartite entanglement can be efficiently and flexibly achieved in a deterministic way with only coherent light fields. This method greatly facilitates the operations in quantum information processing, and holds promising applications in realistic scalable quantum communication and quantum networks. PMID:25316514

Electron-Impact Cross Sections for Ground State to np Excitations of Sodium and Potassium.

PubMed

Stone, Philip M; Kim, Yong-Ki

2004-01-01

Cross sections for electron impact excitation of atoms are important for modeling of low temperature plasmas and gases. While there are many experimental and theoretical results for excitation to the first excited states, little information is available for excitation to higher states. We present here calculations of excitations from the ground state to the np levels of sodium (n = 3 through 11) and potassium (n = 4 through 12). We also present a calculation for a transition from the excited sodium level 3p to 3d to show the generality of the method. Scaling formulas developed earlier by Kim [Phys. Rev. A 64, 032713 (2001)] for plane-wave Born cross sections are used. These formulas have been shown to be remarkably accurate yet simple to use. We have used a core polarization potential in a Dirac-Fock wave function code to calculate target atom wave functions and a matching form of the dipole transition operator to calculate oscillator strengths and Born cross sections. The scaled Born results here for excitation to the first excited levels are in very good agreement with experimental and other theoretical data, and the results for excitation to the next few levels are in satisfactory agreement with the limited data available. The present results for excitation to the higher levels are believed to be the only data available.

Relativistic calculations of atomic properties

NASA Astrophysics Data System (ADS)

Kaur, Jasmeet; Sahoo, B. K.; Arora, Bindiya

2017-04-01

Singly charged ions are engaging candidates in many areas of Physics. They are especially important in astrophysics for evaluating the radiative properties of stellar objects, in optical frequency standards and for fundamental physics studies such as searches for permanent electric dipole moments and atomic parity violation. Interpretation of these experiments often requires a knowledge of their transition wavelengths and electric dipole amplitudes. In this work, we discuss the calculation of various properties of alkaline earth ions. The relativistic all-order SD method in which all single and double excitations of the Dirac-Fock wave function are included, is used to calculate these atomic properties. We use this method for evaluation of electric dipole matrix elements of alkaline earth ions. Combination of these matrix elements with experimental energies allow to obtain the polarizabilities of ground and excited states of ions. We discuss the applications of estimated polarizabiities as a function of imaginary frequencies in the calculations of long-range atom-ion interactions. We have also located the magic wavelengths for nS1 / 2 - nD3 / 2 , 5 / 2 transitions of alkaline earth ions. These calculated properties will be highly valuable to atomic and astrophysics community. UGC-BSR Grant No. F.7-273/2009/BSR.

Dynamic evolution of double Λ five-level atom interacting with one-mode electromagnetic cavity field

NASA Astrophysics Data System (ADS)

Abdel-Wahab, N. H.; Salah, Ahmed

2017-12-01

In this paper, the model describing a double Λ five-level atom interacting with a single mode electromagnetic cavity field in the (off) non-resonate case is studied. We obtained the constants of motion for the considered model. Also, the state vector of the wave function is given by using the Schrödinger equation when the atom is initially prepared in its excited state. The dynamical evolutions for the collapse revivals, the antibunching of photons and the field squeezing phenomena are investigated when the field is considered in a coherent state. The influence of detuning parameters on these phenomena is investigated. We noticed that the atom-field properties are influenced by changing the detuning parameters. The investigation of these aspects by numerical simulations is carried out using the Quantum Toolbox in Python (QuTip).

Creation of Rydberg Polarons in a Bose Gas

NASA Astrophysics Data System (ADS)

Camargo, F.; Schmidt, R.; Whalen, J. D.; Ding, R.; Woehl, G.; Yoshida, S.; Burgdörfer, J.; Dunning, F. B.; Sadeghpour, H. R.; Demler, E.; Killian, T. C.

2018-02-01

We report spectroscopic observation of Rydberg polarons in an atomic Bose gas. Polarons are created by excitation of Rydberg atoms as impurities in a strontium Bose-Einstein condensate. They are distinguished from previously studied polarons by macroscopic occupation of bound molecular states that arise from scattering of the weakly bound Rydberg electron from ground-state atoms. The absence of a p -wave resonance in the low-energy electron-atom scattering in Sr introduces a universal behavior in the Rydberg spectral line shape and in scaling of the spectral width (narrowing) with the Rydberg principal quantum number, n . Spectral features are described with a functional determinant approach (FDA) that solves an extended Fröhlich Hamiltonian for a mobile impurity in a Bose gas. Excited states of polyatomic Rydberg molecules (trimers, tetrameters, and pentamers) are experimentally resolved and accurately reproduced with a FDA.

Revisiting the adsorption of copper-phthalocyanine on Au(111) including van der Waals corrections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lüder, Johann; Eriksson, Olle; Sanyal, Biplab

2014-03-28

We have studied the adsorption of copper-phthalocyanine on Au(111) by means of van der Waals corrected density functional theory using the Tkatchenko-Scheffler method. We have compared the element and site resolved adsorption distances to recent experimental normal-incident X-ray standing wave measurements. The measured adsorption distances could be reproduced within a deviation of 1% for the Cu atom, 1% for the C atoms, and 2% for the N atoms. The molecule was found to have a magnetic moment of 1 μ{sub B} distributed over the Cu and the N atoms of the pyrrole ring. Simulated scanning tunnel microscopy images based onmore » the total and on the spin-resolved differential charge densities are provided for bias voltages of −1.45 and 1.45 eV.« less

Application of P-wave Hybrid Theory to the Scattering of Electrons from He+ and Resonances in He and H ion

NASA Technical Reports Server (NTRS)

Bhatia, A. K.

2012-01-01

The P-wave hybrid theory of electron-hydrogen elastic scattering [Phys. Rev. A 85, 052708 (2012)] is applied to the P-wave scattering from He ion. In this method, both short-range and long-range correlations are included in the Schroedinger equation at the same time, by using a combination of a modified method of polarized orbitals and the optical potential formalism. The short-correlation functions are of Hylleraas type. It is found that the phase shifts are not significantly affected by the modification of the target function by a method similar to the method of polarized orbitals and they are close to the phase shifts calculated earlier by Bhatia [Phys. Rev. A 69, 032714 (2004)]. This indicates that the correlation function is general enough to include the target distortion (polarization) in the presence of the incident electron. The important fact is that in the present calculation, to obtain similar results only a 20-term correlation function is needed in the wave function compared to the 220- term wave function required in the above-mentioned calculation. Results for the phase shifts, obtained in the present hybrid formalism, are rigorous lower bounds to the exact phase shifts. The lowest P-wave resonances in He atom and hydrogen ion have been calculated and compared with the results obtained using the Feshbach projection operator formalism [Phys. Rev. A, 11, 2018 (1975)]. It is concluded that accurate resonance parameters can be obtained by the present method, which has the advantage of including corrections due to neighboring resonances, bound states and the continuum in which these resonance are embedded.

Optical Precursor with Four-Wave Mixing and Storage Based on a Cold-Atom Ensemble

NASA Astrophysics Data System (ADS)

Ding, Dong-Sheng; Jiang, Yun Kun; Zhang, Wei; Zhou, Zhi-Yuan; Shi, Bao-Sen; Guo, Guang-Can

2015-03-01

We observed optical precursors in four-wave mixing based on a cold-atom gas. Optical precursors appear at the edges of pulses of the generated optical field, and propagate through the atomic medium without absorption. Theoretical analysis suggests that these precursors correspond to high-frequency components of the signal pulse, which means the atoms cannot respond quickly to rapid changes in the electromagnetic field. In contrast, the low-frequency signal components are absorbed by the atoms during transmission. We also showed experimentally that the backward precursor can be stored using a Raman transition of the atomic ensemble and retrieved later.

Efficient atom localization via probe absorption in an inverted-Y atomic system

NASA Astrophysics Data System (ADS)

Wu, Jianchun; Wu, Bo; Mao, Jiejian

2018-06-01

The behaviour of atom localization in an inverted-Y atomic system is theoretically investigated. For the atoms interacting with a weak probe field and several orthogonal standing-wave fields, their position information can be obtained by measuring the probe absorption. Compared with the traditional scheme, we couple the probe field to the transition between the middle and top levels. It is found that the probe absorption sensitively depends on the detuning and strength of the relevant light fields. Remarkably, the atom can be localized at a particular position in the standing-wave fields by coupling a microwave field to the transition between the two ground levels.

Faculty Member for Research in an Undergraduate Institution Prize Talk: Research and Teaching through high-precision spectroscopy of heavy atoms

NASA Astrophysics Data System (ADS)

Majumder, Tiku

2017-04-01

In recent decades, substantial experimental effort has centered on heavy (high-Z) atomic and molecular systems for atomic-physics-based tests of standard model physics, through (for example) measurements of atomic parity nonconservation and searches for permanent electric dipole moments. In all of this work, a crucial role is played by atomic theorists, whose accurate wave function calculations are essential in connecting experimental observables to tests of relevant fundamental physics parameters. At Williams College, with essential contributions from dozens of undergraduate students, we have pursued a series of precise atomic structure measurements in heavy metal atoms such as thallium, indium, and lead. These include measurements of hyperfine structure, transition amplitudes, and atomic polarizability. This work, involving diode lasers, heated vapor cells, and an atomic beam apparatus, has both tested the accuracy and helped guide the refinement of new atomic theory calculations. I will discuss a number of our recent experimental results, emphasizing the role played by students and the opportunities that have been afforded for research-training in this undergraduate environment. Work supported by Research Corporation, the NIST Precision Measurement Grants program, and the National Science Foundation.

Retina as Reciprocal Spatial Fourier Transform Space Implies ``Wave-transformation'' Functions, String Theory, the Inappropriate Uncertainty Principle, and Predicts ``Quarked'' Protons.

NASA Astrophysics Data System (ADS)

Mc Leod, Roger David; Mc Leod, David M.

2007-10-01

Vision, via transform space: ``Nature behaves in a reciprocal way;' also, Rect x pressure-input sense-reports as Sinc p, indicating brain interprets reciprocal ``p'' space as object space. Use Mott's and Sneddon's Wave Mechanics and Its Applications. Wave transformation functions are strings of positron, electron, proton, and neutron; uncertainty is a semantic artifact. Neutrino-string de Broglie-Schr"odinger wave-function models for electron, positron, suggest three-quark models for protons, neutrons. Variably vibrating neutrino-quills of this model, with appropriate mass-energy, can be a vertical proton string, quills leftward; thread string circumferentially, forming three interlinked circles with ``overpasses''. Diameters are 2:1:2, center circle has quills radially outward; call it a down quark, charge --1/3, charge 2/3 for outward quills, the up quarks of outer circles. String overlap summations are nodes; nodes also far left and right. Strong nuclear forces may be --px. ``Dislodging" positron with neutrino switches quark-circle configuration to 1:2:1, `downers' outside. Unstable neutron charge is 0. Atoms build. With scale factors, retinal/vision's, and quantum mechanics,' spatial Fourier transforms/inverses are equivalent.

Non-local electron transport through normal and topological ladder-like atomic systems

NASA Astrophysics Data System (ADS)

Kurzyna, Marcin; Kwapiński, Tomasz

2018-05-01

We propose a locally protected ladder-like atomic system (nanoconductor) on a substrate that is insensitive to external perturbations. The system corresponds to coupled atomic chains fabricated on different surfaces. Electron transport properties of such conductors are studied theoretically using the model tight-binding Su-Schriffer-Hegger (SSH) Hamiltonian and Green's function formalism. We have found that the conductance of the system is almost insensitive to single adatoms and oscillates as a function of the side chain length with very large periods. Non-local character of the electron transport was observed also for topological SSH chains where nontrivial end states survive in the presence of disturbances as well as for different substrates. We have found that the careful inspection of the density of states or charge waves can provide the information about the atom energy levels and hopping amplitudes. Moreover, the ladder-like geometry allows one to distinguish between normal and topological zero-energy states. It is important that topological chains do not reveal Friedel oscillations which are observed in non-topological chains.

Molecular dynamics simulation of shock wave and spallation phenomena in metal foils irradiated by femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Zhakhovsky, Vasily; Demaske, Brian; Inogamov, Nail; Oleynik, Ivan

2010-03-01

Femtosecond laser irradiation of metals is an effective technique to create a high-pressure frontal layer of 100-200 nm thickness. The associated ablation and spallation phenomena can be studied in the laser pump-probe experiments. We present results of a large-scale MD simulation of ablation and spallation dynamics developing in 1,2,3μm thick Al and Au foils irradiated by a femtosecond laser pulse. Atomic-scale mechanisms of laser energy deposition, transition from pressure wave to shock, reflection of the shock from the rear-side of the foil, and the nucleation of cracks in the reflected tensile wave, having a very high strain rate, were all studied. To achieve a realistic description of the complex phenomena induced by strong compression and rarefaction waves, we developed new embedded atom potentials for Al and Au based on cold pressure curves. MD simulations revealed the complex interplay between spallation and ablation processes: dynamics of spallation depends on the pressure profile formed in the ablated zone at the early stage of laser energy absorption. It is shown that the essential information such as material properties at high strain rate and spall strength can be extracted from the simulated rear-side surface velocity as a function of time.

Dual-Beam Atom Laser Driven by Spinor Dynamics

NASA Technical Reports Server (NTRS)

Thompson, Robert; Lundblad, Nathan; Maleki, Lute; Aveline, David

2007-01-01

An atom laser now undergoing development simultaneously generates two pulsed beams of correlated Rb-87 atoms. (An atom laser is a source of atoms in beams characterized by coherent matter waves, analogous to a conventional laser, which is a source of coherent light waves.) The pumping mechanism of this atom laser is based on spinor dynamics in a Bose-Einstein condensate. By virtue of the angular-momentum conserving collisions that generate the two beams, the number of atoms in one beam is correlated with the number of atoms in the other beam. Such correlations are intimately linked to entanglement and squeezing in atomic ensembles, and atom lasers like this one could be used in exploring related aspects of Bose-Einstein condensates, and as components of future sensors relying on atom interferometry. In this atom-laser apparatus, a Bose-Einstein condensate of about 2 x 10(exp 6) Rb-87 atoms at a temperature of about 120 micro-K is first formed through all-optical means in a relatively weak singlebeam running-wave dipole trap that has been formed by focusing of a CO2-laser beam. By a technique that is established in the art, the trap is loaded from an ultrahigh-vacuum magnetooptical trap that is, itself, loaded via a cold atomic beam from an upstream two-dimensional magneto-optical trap that resides in a rubidium-vapor cell that is differentially pumped from an adjoining vacuum chamber, wherein are performed scientific observations of the beams ultimately generated by the atom laser.

A note on the accuracy of KS-DFT densities

NASA Astrophysics Data System (ADS)

Ranasinghe, Duminda S.; Perera, Ajith; Bartlett, Rodney J.

2017-11-01

The accuracy of the density of wave function methods and Kohn-Sham (KS) density functionals is studied using moments of the density, ⟨rn ⟩ =∫ ρ (r )rnd τ =∫0∞4 π r2ρ (r ) rnd r ,where n =-1 ,-2,0,1,2 ,and 3 provides information about the short- and long-range behavior of the density. Coupled cluster (CC) singles, doubles, and perturbative triples (CCSD(T)) is considered as the reference density. Three test sets are considered: boron through neon neutral atoms, two and four electron cations, and 3d transition metals. The total density and valence only density are distinguished by dropping appropriate core orbitals. Among density functionals tested, CAMQTP00 and ωB97x show the least deviation for boron through neon neutral atoms. They also show accurate eigenvalues for the HOMO indicating that they should have a more correct long-range behavior for the density. For transition metals, some density functional approximations outperform some wave function methods, suggesting that the KS determinant could be a better starting point for some kinds of correlated calculations. By using generalized many-body perturbation theory (MBPT), the convergence of second-, third-, and fourth-order KS-MBPT for the density is addressed as it converges to the infinite-order coupled cluster result. For the transition metal test set, the deviations in the KS density functional theory methods depend on the amount of exact exchange the functional uses. Functionals with exact exchange close to 25% show smaller deviations from the CCSD(T) density.

Kinetic-energy matrix elements for atomic Hylleraas-CI wave functions.

PubMed

Harris, Frank E

2016-05-28

Hylleraas-CI is a superposition-of-configurations method in which each configuration is constructed from a Slater-type orbital (STO) product to which is appended (linearly) at most one interelectron distance rij. Computations of the kinetic energy for atoms by this method have been difficult due to the lack of formulas expressing these matrix elements for general angular momentum in terms of overlap and potential-energy integrals. It is shown here that a strategic application of angular-momentum theory, including the use of vector spherical harmonics, enables the reduction of all atomic kinetic-energy integrals to overlap and potential-energy matrix elements. The new formulas are validated by showing that they yield correct results for a large number of integrals published by other investigators.

Atomic electron energies including relativistic effects and quantum electrodynamic corrections

NASA Technical Reports Server (NTRS)

Aoyagi, M.; Chen, M. H.; Crasemann, B.; Huang, K. N.; Mark, H.

1977-01-01

Atomic electron energies have been calculated relativistically. Hartree-Fock-Slater wave functions served as zeroth-order eigenfunctions to compute the expectation of the total Hamiltonian. A first order correction to the local approximation was thus included. Quantum-electrodynamic corrections were made. For all orbitals in all atoms with 2 less than or equal to Z less than or equal to 106, the following quantities are listed: total energies, electron kinetic energies, electron-nucleus potential energies, electron-electron potential energies consisting of electrostatic and Breit interaction (magnetic and retardation) terms, and vacuum polarization energies. These results will serve for detailed comparison of calculations based on other approaches. The magnitude of quantum electrodynamic corrections is exhibited quantitatively for each state.

Efimov effect for heteronuclear three-body systems at positive scattering length and finite temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emmons, Samuel B.; Kang, Daekyoung; Acharya, Bijaya

2017-09-08

Here, we study the recombination process of three atoms scattering into an atom and diatomic molecule in heteronuclear mixtures of ultracold atomic gases with large and positive interspecies scattering length at finite temperature. We calculate the temperature dependence of the three-body recombination rates by extracting universal scaling functions that parametrize the energy dependence of the scattering matrix. We compare our results to experimental data for the 40K– 87Rb mixture and make a prediction for 6Li– 87Rb. We find that contributions from higher partial wave channels significantly impact the total rate and, in systems with particularly large mass imbalance, can evenmore » obliterate the recombination minima associated with the Efimov effect.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orlenko, E. V., E-mail: eorlenko@mail.ru; Evstafev, A. V.; Orlenko, F. E.

A formalism of exchange perturbation theory (EPT) is developed for the case of interactions that explicitly depend on time. Corrections to the wave function obtained in any order of perturbation theory and represented in an invariant form include exchange contributions due to intercenter electron permutations in complex multicenter systems. For collisions of atomic systems with an arbitrary type of interaction, general expressions are obtained for the transfer (T) and scattering (S) matrices in which intercenter electron permutations between overlapping nonorthogonal states belonging to different centers (atoms) are consistently taken into account. The problem of collision of alpha particles with lithiummore » atoms accompanied by the redistribution of electrons between centers is considered. The differential and total charge-exchange cross sections of lithium are calculated.« less

Parity oscillations and photon correlation functions in the Z2-U (1 ) Dicke model at a finite number of atoms or qubits

NASA Astrophysics Data System (ADS)

Yi-Xiang, Yu; Ye, Jinwu; Zhang, CunLin

2016-08-01

Four standard quantum optics models, that is, the Rabi, Dicke, Jaynes-Cummings, and Tavis-Cummings models, were proposed by physicists many decades ago. Despite their relative simple forms and many previous theoretical works, their physics at a finite N , especially inside the superradiant regime, remain unknown. In this work, by using the strong-coupling expansion and exact diagonalization (ED), we study the Z2-U(1 ) Dicke model with independent rotating-wave coupling g and counterrotating-wave coupling g' at a finite N . This model includes the four standard quantum optics models as its various special limits. We show that in the superradiant phase, the system's energy levels are grouped into doublets with even and odd parity. Any anisotropy β =g'/g ≠1 leads to the oscillation of parities in both the ground and excited doublets as the atom-photon coupling strength increases. The oscillations will be pushed to the infinite coupling strength in the isotropic Z2 limit β =1 . We find nearly perfect agreement between the strong-coupling expansion and the ED in the superradiant regime when β is not too small. We also compute the photon correlation functions, squeezing spectrum, and number correlation functions that can be measured by various standard optical techniques.

The Transcorrelated Method Combined with the Variational Monte Carlo Calculation: Application to Atoms

NASA Astrophysics Data System (ADS)

Umezawa, Naoto; Tsuneyuki, Shinji; Ohno, Takahisa; Shiraishi, Kenji; Chikyow, Toyohiro

2005-03-01

The transcorrelated (TC) method is a useful approach to optimize the Jastrow-Slater-type many-body wave function FD. The basic idea of the TC method [1] is based on the similarity transformation of a many-body Hamiltonian H with respect to the Jastrow factor F: HTC=frac1F H F in order to incorporate the correlation effect into HTC. Both the F and D are optimized by minimizing the variance ^2=|Hrm TCD - E D |^2 d^3N x. The optimization for F is implemented by the variational Monte Carlo calculation, and D is determined by the TC self-consistent-field equation for the one-body wave functions φμ(x), which is derived from the functional derivative of ^2 with respect to φmu(x). In this talk, we will present the results given by the transcorrelated variational Monte Carlo (TC-VMC) method for the ground state [2] and the excited states of atoms [3]. [1]S. F. Boys and N. C. Handy, Proc. Roy. Soc. A, 309, 209; 310, 43; 310, 63; 311, 309 (1969). [2]N. Umezawa and S. Tsuneyuki, J. Chem. Phys. 119, 10015 (2003). [3]N. Umezawa and S. Tsuneyuki, J. Chem. Phys. 121, 7070 (2004).

Tunable optical and excitonic properties of phosphorene via oxidation

NASA Astrophysics Data System (ADS)

Sadki, S.; Drissi, L. B.

2018-06-01

The optical properties and excitonic wave function of phosphorene oxides (PO) are studied using the first principle many-body Green function and the Bethe–Salpeter equation formalism. In this work, the optical properties are determined using ab initio calculations of the dielectric function. At the long wavelength limit q of EM wave (i.e. ), the dielectric function, the absorption spectrum, the lectivity, the electron energy loss spectra (EELS) and the wave function are calculated. The results show an excitonic binding energy of 818 meV with a bright exciton located in the armchair direction in pristine phosphorene. For PO, the arrangement of the oxygen atoms significantly influences the optical properties. In particular, the absorption spectrum is extended along the solar spectrum, with a high absorption coefficient observed in the dangling structures. The maximum lectivity values are observed for the high energies of the light spectrum. Moreover, the first EELS peak is located in the visible region in all the structures except for one configuration that exhibits the same behavior as pure phosphorene. Finally, the exciton effect reveals that all PO conformers have a dark exciton state, which is suitable for long-lived applications.

Spatial transport of electron quantum states with strong attosecond pulses

NASA Astrophysics Data System (ADS)

Chovancova, M.; Agueny, H.; Førre, M.; Kocbach, L.; Hansen, J. P.

2017-11-01

This work follows up the work of Dimitrovsky, Briggs and co-workers on translated electron atomic states by a strong field of an atto-second laser pulse, also described as creation of atoms without a nucleus. Here, we propose a new approach by analyzing the electron states in the Kramers-Henneberger moving frame in the dipole approximation. The wave function follows the displacement vector α (t). This allows arbitrarily shaped pulses, including the model delta-function potentials in the Dimitrovsky and Briggs approach. In the case of final-length single-cycle pulses, we apply both the Kramers-Henneberger moving frame analysis and a full numerical treatment of our 1D model. When the laser pulse frequency exceeds the frequency associated by the energy difference between initial and final states, the entire wavefunction is translated in space nearly without loss of coherence, to a well defined distance from the original position where the ionized core is left behind. This statement is demonstrated on the excited Rydberg states (n = 10, n = 15), where almost no distortion in the transported wave functions has been observed. However, the ground state (n = 1) is visibly distorted during the removal by pulses of reasonable frequencies, as also predicted by Dimitrovsky and Briggs analysis. Our approach allows us to analyze general pulses as well as the model delta-function potentials on the same footing in the Kramers-Henneberger frame.

An array of correlated atom interferometers to study to study the local fluctuations of the gravitational field and its impact on low fequency gravitational waves observations

NASA Astrophysics Data System (ADS)

Bouyer, P.; Canuel, B.; Pelisson, S.; Harms, J.; Bertoldi, A.; Gaffet, S.; Landragin, A.; Lefevre, G.; Riou, I.; Geiger, R.

2016-12-01

We will present here the Matter-Wave laser Interferometer Gravitation Antenna, MIGA, a hybrid instrument composed of a network of atom interferometers horizontally aligned and interrogated by the resonant field of an optical cavity. This detector will provide measurements of sub Hertz variations of the gravitational strain tensor. MIGA will bring new methods for geophysics for the characterization of spatial and temporal variations of the local gravity field and will also be a demonstrator for future low frequency Gravitational Wave (GW) detections. The recent first direct observation of gravitational radiation opens the way towards a novel astronomy requires a new class of low frequency Gravitational Wave detectors such as MIGA. Nevertheless, the fluctuations of the Earth gravitational field over different baselines are of high relevance for the functioning of such experiments. Indeed, a fluctuating gravity gradient causes a tidal effect that cannot, in principle, be distinguished from Gravitational Waves.This so-called « Newtonian Noise » is therefore considered up to now as a fundamental limit for any ground based detector and the main reason for restricting future low frequency GW detectors to space. Nevertheless, these two contributions may become discernible by the use of a network of test masses. Indeed, both GW and NN effects will have different spatial signatures over the test mass network. While GW has extremely long characteristic length, NN has shorter characteristic lengths going from the meter to a few kilometers.The array of distant Atom Interferometers in MIGA can be used as network of test masses, which can be correlated using a common laser link. Differential measurements between the atom interferometers of the Network enables for a large reduction of the effect of NN and opens the way towards the realization of low frequency GW detectors.In this paper, we will detail the projection of background NN in the underground environment of the LSBB and present GW interferometer geometries enabling its reduction.

Collective emission of matter-wave jets from driven Bose-Einstein condensates.

PubMed

Clark, Logan W; Gaj, Anita; Feng, Lei; Chin, Cheng

2017-11-16

Scattering is used to probe matter and its interactions in all areas of physics. In ultracold atomic gases, control over pairwise interactions enables us to investigate scattering in quantum many-body systems. Previous experiments on colliding Bose-Einstein condensates have revealed matter-wave interference, haloes of scattered atoms, four-wave mixing and correlations between counter-propagating pairs. However, a regime with strong stimulation of spontaneous collisions analogous to superradiance has proved elusive. In this regime, the collisions rapidly produce highly correlated states with macroscopic population. Here we find that runaway stimulated collisions in Bose-Einstein condensates with periodically modulated interaction strength cause the collective emission of matter-wave jets that resemble fireworks. Jets appear only above a threshold modulation amplitude and their correlations are invariant even when the number of ejected atoms grows exponentially. Hence, we show that the structures and atom occupancies of the jets stem from the quantum fluctuations of the condensate. Our findings demonstrate the conditions required for runaway stimulated collisions and reveal the quantum nature of matter-wave emission.

The Independent Gradient Model: A New Approach for Probing Strong and Weak Interactions in Molecules from Wave Function Calculations.

PubMed

Lefebvre, Corentin; Khartabil, Hassan; Boisson, Jean-Charles; Contreras-García, Julia; Piquemal, Jean-Philip; Hénon, Eric

2018-03-19

Extraction of the chemical interaction signature from local descriptors based on electron density (ED) is still a fruitful field of development in chemical interpretation. In a previous work that used promolecular ED (frozen ED), the new descriptor, δg , was defined. It represents the difference between a virtual upper limit of the ED gradient (∇ρIGM , IGM=independent gradient model) that represents a noninteracting system and the true ED gradient (∇ρ ). It can be seen as a measure of electron sharing brought by ED contragradience. A compelling feature of this model is to provide an automatic workflow that extracts the signature of interactions between selected groups of atoms. As with the noncovalent interaction (NCI) approach, it provides chemists with a visual understanding of the interactions present in chemical systems. ∇ρIGM is achieved simply by using absolute values upon summing the individual gradient contributions that make up the total ED gradient. Hereby, we extend this model to relaxed ED calculated from a wave function. To this end, we formulated gradient-based partitioning (GBP) to assess the contribution of each orbital to the total ED gradient. We highlight these new possibilities across two prototypical examples of organic chemistry: the unconventional hexamethylbenzene dication, with a hexa-coordinated carbon atom, and β-thioaminoacrolein. It will be shown how a bond-by-bond picture can be obtained from a wave function, which opens the way to monitor specific interactions along reaction paths. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Matter-wave entanglement and teleportation by molecular dissociation and collisions.

PubMed

Opatrný, T; Kurizki, G

2001-04-02

We propose dissociation of cold diatomic molecules as a source of atom pairs with highly correlated (entangled) positions and momenta, approximating the original quantum state introduced by Einstein, Podolsky, and Rosen (EPR) [Phys. Rev. 47, 777 (1935)]. Wave packet teleportation is shown to be achievable by its collision with one of the EPR correlated atoms and manipulation of the other atom in the pair.

Matter-Wave Entanglement and Teleportation by Molecular Dissociation and Collisions

NASA Astrophysics Data System (ADS)

Opatrný, T.; Kurizki, G.

2001-04-01

We propose dissociation of cold diatomic molecules as a source of atom pairs with highly correlated (entangled) positions and momenta, approximating the original quantum state introduced by Einstein, Podolsky, and Rosen (EPR) [Phys. Rev. 47, 777 (1935)]. Wave packet teleportation is shown to be achievable by its collision with one of the EPR correlated atoms and manipulation of the other atom in the pair.

Radiation force on a single atom in a cavity

NASA Technical Reports Server (NTRS)

Kim, M. S.

1992-01-01

We consider the radiation pressure microscopically. Two perfectly conducting plates are parallelly placed in a vacuum. As the vacuum field hits the plates they get pressure from the vacuum. The excessive outside modes of the vacuum field push the plates together, which is known as the Casimer force. We investigate the quantization of the standing wave between the plates to study the interaction between this wave and the atoms on the plates or between the plates. We show that even the vacuum field pushes the atom to place it at nodes of the standing wave.

Guitar Strings as Standing Waves: A Demonstration

NASA Astrophysics Data System (ADS)

Davis, Michael

2007-08-01

An undergraduate student's first exposure to modern atomic theory tends to start with Bohr's model of the atom. This familiar introduction to atomic structure also marks a general chemistry student's first foray into waves. Many popular chemistry textbooks illustrate the concept of a standing wave in the development of the modern quantum model by using the phrase “as seen on a guitar string”. In these illustrations, the wave itself is often small and difficult to discern. The same phenomenon, however, can be easily and audibly observed. This demonstration uses an acoustic guitar to produce three unique harmonic vibrations, each of which is representative of a standing wave and illustrates the concept of quantization. Manipulation of the guitar string to produce a standing wave is pervasive in popular music and is audibly recognizable. Lightly placing a finger on the 12th, 7th, or 5th fret and strumming any one or all six strings can produce an audible example of a standing wave on a guitar. This corresponds to a standing wave with 1, 2, or 3 nodes, respectively. Attempting to induce a node at other points on a guitar string does not generate a standing wave, due to destructive interference, thus no audible tone is produced.

Basis convergence of range-separated density-functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franck, Odile, E-mail: odile.franck@etu.upmc.fr; Mussard, Bastien, E-mail: bastien.mussard@upmc.fr; CNRS, UMR 7616, Laboratoire de Chimie Théorique, F-75005 Paris

2015-02-21

Range-separated density-functional theory (DFT) is an alternative approach to Kohn-Sham density-functional theory. The strategy of range-separated density-functional theory consists in separating the Coulomb electron-electron interaction into long-range and short-range components and treating the long-range part by an explicit many-body wave-function method and the short-range part by a density-functional approximation. Among the advantages of using many-body methods for the long-range part of the electron-electron interaction is that they are much less sensitive to the one-electron atomic basis compared to the case of the standard Coulomb interaction. Here, we provide a detailed study of the basis convergence of range-separated density-functional theory. Wemore » study the convergence of the partial-wave expansion of the long-range wave function near the electron-electron coalescence. We show that the rate of convergence is exponential with respect to the maximal angular momentum L for the long-range wave function, whereas it is polynomial for the case of the Coulomb interaction. We also study the convergence of the long-range second-order Møller-Plesset correlation energy of four systems (He, Ne, N{sub 2}, and H{sub 2}O) with cardinal number X of the Dunning basis sets cc − p(C)V XZ and find that the error in the correlation energy is best fitted by an exponential in X. This leads us to propose a three-point complete-basis-set extrapolation scheme for range-separated density-functional theory based on an exponential formula.« less

Continuous wave cavity ring-down spectroscopy for velocity distribution measurements in plasma.

PubMed

McCarren, D; Scime, E

2015-10-01

We report the development of a continuous wave cavity ring-down spectroscopic (CW-CRDS) diagnostic for real-time, in situ measurement of velocity distribution functions of ions and neutral atoms in plasma. This apparatus is less complex than conventional CW-CRDS systems. We provide a detailed description of the CW-CRDS apparatus as well as measurements of argon ions and neutrals in a high-density (10(9) cm(-3) < plasma density <10(13) cm(-3)) plasma. The CW-CRDS measurements are validated through comparison with laser induced fluorescence measurements of the same absorbing states of the ions and neutrals.

Measuring and engineering the atomic mass density wave of a Gaussian mass-polariton pulse in optical fibers

NASA Astrophysics Data System (ADS)

Partanen, Mikko; Tulkki, Jukka

2018-02-01

Conventional theories of electromagnetic waves in a medium assume that only the energy of the field propagates inside the medium. Consequently, they neglect the transport of mass density by the medium atoms. We have recently presented foundations of a covariant theory of light propagation in a nondispersive medium by considering a light wave simultaneously with the dynamics of the medium atoms driven by optoelastic forces [Phys. Rev. A 95, 063850 (2017)]. In particular, we have shown that the mass is transferred by an atomic mass density wave (MDW), which gives rise to mass-polariton (MP) quasiparticles, i.e., covariant coupled states of the field and matter having a nonzero rest mass. Another key observation of the mass-polariton theory of light is that, in common semiconductors, most of the momentum of light is transferred by moving atoms, e.g., 92% in the case of silicon. In this work, we generalize the MP theory of light for dispersive media and consider experimental measurement of the mass transferred by the MDW atoms when an intense light pulse propagates in a silicon fiber. In particular, we consider optimal intensity and time dependence of a Gaussian pulse and account for the breakdown threshold irradiance of the material. The optical shock wave property of the MDW, which propagates with the velocity of light instead of the velocity of sound, prompts for engineering of novel device concepts like very high frequency mechanical oscillators not limited by the acoustic cutoff frequency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryu, C.; Boshier, M. G.

An integrated coherent matter wave circuit is a single device, analogous to an integrated optical circuit, in which coherent de Broglie waves are created and then launched into waveguides where they can be switched, divided, recombined, and detected as they propagate. Applications of such circuits include guided atom interferometers, atomtronic circuits, and precisely controlled delivery of atoms. We report experiments demonstrating integrated circuits for guided coherent matter waves. The circuit elements are created with the painted potential technique, a form of time-averaged optical dipole potential in which a rapidly moving, tightly focused laser beam exerts forces on atoms through theirmore » electric polarizability. Moreover, the source of coherent matter waves is a Bose–Einstein condensate (BEC). Finally, we launch BECs into painted waveguides that guide them around bends and form switches, phase coherent beamsplitters, and closed circuits. These are the basic elements that are needed to engineer arbitrarily complex matter wave circuitry.« less

An atomic gravitational wave interferometric sensor in low earth orbit (AGIS-LEO)

NASA Astrophysics Data System (ADS)

Hogan, Jason M.; Johnson, David M. S.; Dickerson, Susannah; Kovachy, Tim; Sugarbaker, Alex; Chiow, Sheng-Wey; Graham, Peter W.; Kasevich, Mark A.; Saif, Babak; Rajendran, Surjeet; Bouyer, Philippe; Seery, Bernard D.; Feinberg, Lee; Keski-Kuha, Ritva

2011-07-01

We propose an atom interferometer gravitational wave detector in low Earth orbit (AGIS-LEO). Gravitational waves can be observed by comparing a pair of atom interferometers separated by a 30 km baseline. In the proposed configuration, one or three of these interferometer pairs are simultaneously operated through the use of two or three satellites in formation flight. The three satellite configuration allows for the increased suppression of multiple noise sources and for the detection of stochastic gravitational wave signals. The mission will offer a strain sensitivity of {<10^{-18}/sqrt{Hz}} in the 50mHz-10Hz frequency range, providing access to a rich scientific region with substantial discovery potential. This band is not currently addressed with the LIGO, VIRGO, or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Finally, we present a brief conceptual overview of shorter-baseline ({lesssim100 m}) atom interferometer configurations that could be deployed as proof-of-principle instruments on the International Space Station (AGIS-ISS) or an independent satellite.

Quantum interference between two phonon paths and reduced heat transport in diamond lattice with atomic-scale planar defects

NASA Astrophysics Data System (ADS)

Kosevich, Yu. A.; Strelnikov, I. A.

2018-02-01

Destructive quantum interference between the waves propagating through laterally inhomogeneous layer can result in their total reflection, which in turn reduces energy flux carried by these waves. We consider the systems of Ge atoms, which fully or partly, in the chequer-wise order, fill a crystal plane in diamond-like Si lattice. We have revealed that a single type of the atomic defects, which are placed in identical positions in different unit cells in the defect crystal plane, can result in double transmission antiresonances of phonon wave packets. This new effect we relate with the complex structure of the diamond-like unit cell, which comprises two atoms in different positions and results in two distinct vibration resonances in two interfering phonon paths. We also consider the propagation of phonon wave packets in the superlatticies made of the defect planes, half-filled in the chequer-wise order with Ge atoms. We have revealed relatively broad phonon stop bands with center frequencies at the transmission antiresonances. We elaborate the equivalent analytical quasi-1D lattice model of the two phonon paths through the complex planar defect in the diamond-like lattice and describe the reduction of phonon heat transfer through the atomic-scale planar defects.

Quantum Optics in Phase Space

NASA Astrophysics Data System (ADS)

Schleich, Wolfgang P.

2001-04-01

Quantum Optics in Phase Space provides a concise introduction to the rapidly moving field of quantum optics from the point of view of phase space. Modern in style and didactically skillful, Quantum Optics in Phase Space prepares students for their own research by presenting detailed derivations, many illustrations and a large set of workable problems at the end of each chapter. Often, the theoretical treatments are accompanied by the corresponding experiments. An exhaustive list of references provides a guide to the literature. Quantum Optics in Phase Space also serves advanced researchers as a comprehensive reference book. Starting with an extensive review of the experiments that define quantum optics and a brief summary of the foundations of quantum mechanics the author Wolfgang P. Schleich illustrates the properties of quantum states with the help of the Wigner phase space distribution function. His description of waves ala WKB connects semi-classical phase space with the Berry phase. These semi-classical techniques provide deeper insight into the timely topics of wave packet dynamics, fractional revivals and the Talbot effect. Whereas the first half of the book deals with mechanical oscillators such as ions in a trap or atoms in a standing wave the second half addresses problems where the quantization of the radiation field is of importance. Such topics extensively discussed include optical interferometry, the atom-field interaction, quantum state preparation and measurement, entanglement, decoherence, the one-atom maser and atom optics in quantized light fields. Quantum Optics in Phase Space presents the subject of quantum optics as transparently as possible. Giving wide-ranging references, it enables students to study and solve problems with modern scientific literature. The result is a remarkably concise yet comprehensive and accessible text- and reference book - an inspiring source of information and insight for students, teachers and researchers alike.

Production of confluent hypergeometric beam by computer-generated hologram

NASA Astrophysics Data System (ADS)

Chen, Jiannong; Wang, Gang; Xu, Qinfeng

2011-02-01

Because of their spiral wave front, phase singularity, zero-intensity center and orbital angular momentum, dark hollow vortex beams have been found many applications in the field of atom optics such as atom cooling, atom transport and atom guiding. In this paper, a method for generating confluent hypergeometric beam by computer-generated hologram displayed on the spatial light modulator is presented. The hologram is formed by interference between a single ring Laguerre-Gaussian beam and a plane wave. The far-field Fraunhofer diffraction of this optical field transmitted from the hologram is the confluent hypergeometric beam. This beam is a circular symmetric beam which has a phase singularity, spiral wave front, zero-intensity center, and intrinsic orbital angular momentum. It is a new dark hollow vortex beam.

Can even-order laser harmonics exhibited by Bohmian trajectories in symmetric potentials be observed?

PubMed

Peatross, J; Johansen, J

2014-01-13

Strong-field laser-atom interactions provide extreme conditions that may be useful for investigating the de Broglie-Bohm quantum interpretation. Bohmian trajectories representing bound electrons in individual atoms exhibit both even and odd harmonic motion when subjected to a strong external laser field. The phases of the even harmonics depend on the random initial positions of the trajectories within the wave function, making the even harmonics incoherent. In contrast, the phases of odd harmonics remain for the most part coherent regardless of initial position. Under the conjecture that a Bohmian point particle plays the role of emitter, this suggests an experiment to determine whether both even and odd harmonics are produced at the atomic level. Estimates suggest that incoherent emission of even harmonics may be detectable out the side of an intense laser focus interacting with a large number of atoms.

A Density Functional Study of Atomic Hydrogen and Oxygen Chemisorptions on the (0001) Surface of Double Hexagonal Close Packed Americium

NASA Astrophysics Data System (ADS)

Dholabhai, Pratik; Atta-Fynn, Raymond; Ray, Asok

2008-03-01

Ab initio total energy calculations within the framework of density functional theory have been performed for atomic hydrogen and oxygen chemisorptions on the (0001) surface of double hexagonal packed americium using a full-potential all-electron linearized augmented plane wave plus local orbitals (FLAPW+lo) method. The three-fold hollow hcp site was found to be the most stable site for H adsorption, while the two-fold bridge adsorption site was found to be the most stable site for O adsorption. Chemisorption energies and adsorption geometries for different adsorption sites will be discussed. The change in work functions, magnetic moments, partial charges inside muffin-tins, difference charge density distributions and density of states for the bare Am slab and the Am slab after adsorption of the adatom will be discussed. The implications of chemisorption on Am 5f electron localization-delocalization will also be discussed.

Dielectric function for doped graphene layer with barium titanate

NASA Astrophysics Data System (ADS)

Martinez Ramos, Manuel; Garces Garcia, Eric; Magana, Fernado; Vazquez Fonseca, Gerardo Jorge

2015-03-01

The aim of our study is to calculate the dielectric function for a system formed with a graphene layer doped with barium titanate. Density functional theory, within the local density approximation, plane-waves and pseudopotentials scheme as implemented in Quantum Espresso suite of programs was used. We considered 128 carbon atoms with a barium titanate cluster of 11 molecules as unit cell with periodic conditions. The geometry optimization is achieved. Optimization of structural configuration is performed by relaxation of all atomic positions to minimize their total energies. Band structure, density of states and linear optical response (the imaginary part of dielectric tensor) were calculated. We thank Dirección General de Asuntos del Personal Académico de la Universidad Nacional Autónoma de México, partial financial support by Grant IN-106514 and we also thank Miztli Super-Computing center the technical assistance.

Seniority and orbital symmetry as tools for establishing a full configuration interaction hierarchy.

PubMed

Bytautas, Laimutis; Henderson, Thomas M; Jiménez-Hoyos, Carlos A; Ellis, Jason K; Scuseria, Gustavo E

2011-07-28

We explore the concept of seniority number (defined as the number of unpaired electrons in a determinant) when applied to the problem of electron correlation in atomic and molecular systems. Although seniority is a good quantum number only for certain model Hamiltonians (such as the pairing Hamiltonian), we show that it provides a useful partitioning of the electronic full configuration interaction (FCI) wave function into rapidly convergent Hilbert subspaces whose weight diminishes as its seniority number increases. The primary focus of this study is the adequate description of static correlation effects. The examples considered are the ground states of the helium, beryllium, and neon atoms, the symmetric dissociation of the N(2) and CO(2) molecules, as well as the symmetric dissociation of an H(8) hydrogen chain. It is found that the symmetry constraints that are normally placed on the spatial orbitals greatly affect the convergence rate of the FCI expansion. The energy relevance of the seniority zero sector (determinants with all paired electrons) increases dramatically if orbitals of broken spatial symmetry (as those commonly used for Hubbard Hamiltonian studies) are allowed in the wave function construction. © 2011 American Institute of Physics

SU-C-204-03: DFT Calculations of the Stability of DOTA-Based-Radiopharmaceuticals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khabibullin, A.R.; Woods, L.M.; Karolak, A.

2016-06-15

Purpose: Application of the density function theory (DFT) to investigate the structural stability of complexes applied in cancer therapy consisting of the 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelated to Ac225, Fr221, At217, Bi213, and Gd68 radio-nuclei. Methods: The possibility to deliver a toxic payload directly to tumor cells is a highly desirable aim in targeted alpha particle therapy. The estimation of bond stability between radioactive atoms and the DOTA chelating agent is the key element in understanding the foundations of this delivery process. Thus, we adapted the Vienna Ab-initio Simulation Package (VASP) with the projector-augmented wave method and a plane-wave basis setmore » in order to study the stability and electronic properties of DOTA ligand chelated to radioactive isotopes. In order to count for the relativistic effect of radioactive isotopes we included Spin-Orbit Coupling (SOC) in the DFT calculations. Five DOTA complex structures were represented as unit cells, each containing 58 atoms. The energy optimization was performed for all structures prior to calculations of electronic properties. Binding energies, electron localization functions as well as bond lengths between atoms were estimated. Results: Calculated binding energies for DOTA-radioactive atom systems were −17.792, −5.784, −8.872, −13.305, −18.467 eV for Ac, Fr, At, Bi and Gd complexes respectively. The displacements of isotopes in DOTA cages were estimated from the variations in bond lengths, which were within 2.32–3.75 angstroms. The detailed representation of chemical bonding in all complexes was obtained with the Electron Localization Function (ELF). Conclusion: DOTA-Gd, DOTA-Ac and DOTA-Bi were the most stable structures in the group. Inclusion of SOC had a significant role in the improvement of DFT calculation accuracy for heavy radioactive atoms. Our approach is found to be proper for the investigation of structures with DOTA-based-radiopharmaceuticals and will enhance our understanding of processes occurring at subatomic levels.« less

Free-space microwave-to-optical conversion via six-wave mixing in Rydberg atoms

NASA Astrophysics Data System (ADS)

Han, Jingshan; Vogt, Thibault; Gross, Christian; Jaksch, Dieter; Kiffner, Martin; Li, Wenhui

2017-04-01

The interconversion of millimeter waves and optical fields is an important and highly topical subject for classical and quantum technologies. In this talk, we report an experimental demonstration of coherent and efficient microwave-to-optical conversion in free space via six-wave mixing in Rydberg atoms. Our scheme utilizes the strong coupling of millimeter waves to Rydberg atoms as well as the frequency mixing based on electromagnetically induced transparency (EIT) that greatly enhances the nonlinearity for the conversion process. We achieve a free-space conversion efficiency of 0.25% with a bandwidth of about 4 MHz in our experiment. Optimized geometry and energy level configurations should enable the broadband interconversion of microwave and optical fields with near-unity efficiency. These results indicate the tremendous potential of Rydberg atoms for the efficient conversion between microwave and optical fields, and thus paves the way to many applications. This work is supported by Singapore Ministry of Education Academic Research Fund Tier 2 (Grant No. MOE2015-T2-1-085).

Calculations of atomic magnetic nuclear shielding constants based on the two-component normalized elimination of the small component method

NASA Astrophysics Data System (ADS)

Yoshizawa, Terutaka; Zou, Wenli; Cremer, Dieter

2017-04-01

A new method for calculating nuclear magnetic resonance shielding constants of relativistic atoms based on the two-component (2c), spin-orbit coupling including Dirac-exact NESC (Normalized Elimination of the Small Component) approach is developed where each term of the diamagnetic and paramagnetic contribution to the isotropic shielding constant σi s o is expressed in terms of analytical energy derivatives with regard to the magnetic field B and the nuclear magnetic moment 𝝁 . The picture change caused by renormalization of the wave function is correctly described. 2c-NESC/HF (Hartree-Fock) results for the σiso values of 13 atoms with a closed shell ground state reveal a deviation from 4c-DHF (Dirac-HF) values by 0.01%-0.76%. Since the 2-electron part is effectively calculated using a modified screened nuclear shielding approach, the calculation is efficient and based on a series of matrix manipulations scaling with (2M)3 (M: number of basis functions).

Projected Hybrid Orbitals: A General QM/MM Method

PubMed Central

2015-01-01

A projected hybrid orbital (PHO) method was described to model the covalent boundary in a hybrid quantum mechanical and molecular mechanical (QM/MM) system. The PHO approach can be used in ab initio wave function theory and in density functional theory with any basis set without introducing system-dependent parameters. In this method, a secondary basis set on the boundary atom is introduced to formulate a set of hybrid atomic orbtials. The primary basis set on the boundary atom used for the QM subsystem is projected onto the secondary basis to yield a representation that provides a good approximation to the electron-withdrawing power of the primary basis set to balance electronic interactions between QM and MM subsystems. The PHO method has been tested on a range of molecules and properties. Comparison with results obtained from QM calculations on the entire system shows that the present PHO method is a robust and balanced QM/MM scheme that preserves the structural and electronic properties of the QM region. PMID:25317748

Macroscopic quantum interference from atomic tunnel arrays

PubMed

Anderson; Kasevich

1998-11-27

Interference of atomic de Broglie waves tunneling from a vertical array of macroscopically populated traps has been observed. The traps were located in the antinodes of an optical standing wave and were loaded from a Bose-Einstein condensate. Tunneling was induced by acceleration due to gravity, and interference was observed as a train of falling pulses of atoms. In the limit of weak atomic interactions, the pulse frequency is determined by the gravitational potential energy difference between adjacent potential wells. The effect is closely related to the ac Josephson effect observed in superconducting electronic systems.

Accuracy of free energies of hydration using CM1 and CM3 atomic charges.

PubMed

Udier-Blagović, Marina; Morales De Tirado, Patricia; Pearlman, Shoshannah A; Jorgensen, William L

2004-08-01

Absolute free energies of hydration (DeltaGhyd) have been computed for 25 diverse organic molecules using partial atomic charges derived from AM1 and PM3 wave functions via the CM1 and CM3 procedures of Cramer, Truhlar, and coworkers. Comparisons are made with results using charges fit to the electrostatic potential surface (EPS) from ab initio 6-31G* wave functions and from the OPLS-AA force field. OPLS Lennard-Jones parameters for the organic molecules were used together with the TIP4P water model in Monte Carlo simulations with free energy perturbation theory. Absolute free energies of hydration were computed for OPLS united-atom and all-atom methane by annihilating the solutes in water and in the gas phase, and absolute DeltaGhyd values for all other molecules were computed via transformation to one of these references. Optimal charge scaling factors were determined by minimizing the unsigned average error between experimental and calculated hydration free energies. The PM3-based charge models do not lead to lower average errors than obtained with the EPS charges for the subset of 13 molecules in the original study. However, improvement is obtained by scaling the CM1A partial charges by 1.14 and the CM3A charges by 1.15, which leads to average errors of 1.0 and 1.1 kcal/mol for the full set of 25 molecules. The scaled CM1A charges also yield the best results for the hydration of amides including the E/Z free-energy difference for N-methylacetamide in water. Copyright 2004 Wiley Periodicals, Inc.

A density difference based analysis of orbital-dependent exchange-correlation functionals

NASA Astrophysics Data System (ADS)

Grabowski, Ireneusz; Teale, Andrew M.; Fabiano, Eduardo; Śmiga, Szymon; Buksztel, Adam; Della Sala, Fabio

2014-03-01

We present a density difference based analysis for a range of orbital-dependent Kohn-Sham functionals. Results for atoms, some members of the neon isoelectronic series and small molecules are reported and compared with ab initio wave function calculations. Particular attention is paid to the quality of approximations to the exchange-only optimised effective potential (OEP) approach: we consider both the localised Hartree-Fock as well as the Krieger-Li-Iafrate methods. Analysis of density differences at the exchange-only level reveals the impact of the approximations on the resulting electronic densities. These differences are further quantified in terms of the ground state energies, frontier orbital energy differences and highest occupied orbital energies obtained. At the correlated level, an OEP approach based on a perturbative second-order correlation energy expression is shown to deliver results comparable with those from traditional wave function approaches, making it suitable for use as a benchmark against which to compare standard density functional approximations.

-X Mixing in T- and V-Shaped Quantum Wires

NASA Astrophysics Data System (ADS)

di Carlo, A.; Pescetelli, S.; Kavokin, A.; Vladimirova, M.; Lugli, P.

1997-11-01

We have applied both tight-binding (TB) and multivalley envelope function (MEF) techniques to calculate the electronic states in T- and V-shaped realistic quantum wires taking into account -X mixing in the conduction band. Strong reduction of the electron quantization energy due to the off-resonant -X mixing has been found in all types of quantum wires. This effect appears to be tied to the localization of the electron wave function and to its overlap with atomic layers next to interfaces.

An open-source framework for analyzing N-electron dynamics. II. Hybrid density functional theory/configuration interaction methodology.

PubMed

Hermann, Gunter; Pohl, Vincent; Tremblay, Jean Christophe

2017-10-30

In this contribution, we extend our framework for analyzing and visualizing correlated many-electron dynamics to non-variational, highly scalable electronic structure method. Specifically, an explicitly time-dependent electronic wave packet is written as a linear combination of N-electron wave functions at the configuration interaction singles (CIS) level, which are obtained from a reference time-dependent density functional theory (TDDFT) calculation. The procedure is implemented in the open-source Python program detCI@ORBKIT, which extends the capabilities of our recently published post-processing toolbox (Hermann et al., J. Comput. Chem. 2016, 37, 1511). From the output of standard quantum chemistry packages using atom-centered Gaussian-type basis functions, the framework exploits the multideterminental structure of the hybrid TDDFT/CIS wave packet to compute fundamental one-electron quantities such as difference electronic densities, transient electronic flux densities, and transition dipole moments. The hybrid scheme is benchmarked against wave function data for the laser-driven state selective excitation in LiH. It is shown that all features of the electron dynamics are in good quantitative agreement with the higher-level method provided a judicious choice of functional is made. Broadband excitation of a medium-sized organic chromophore further demonstrates the scalability of the method. In addition, the time-dependent flux densities unravel the mechanistic details of the simulated charge migration process at a glance. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Realization of localized Bohr-like wave packets.

PubMed

Mestayer, J J; Wyker, B; Lancaster, J C; Dunning, F B; Reinhold, C O; Yoshida, S; Burgdörfer, J

2008-06-20

We demonstrate a protocol to create localized wave packets in very-high-n Rydberg states which travel in nearly circular orbits around the nucleus. Although these wave packets slowly dephase and eventually lose their localization, their motion can be monitored over several orbital periods. These wave packets represent the closest analog yet achieved to the original Bohr model of the hydrogen atom, i.e., an electron in a circular classical orbit around the nucleus. The possible extension of the approach to create "planetary atoms" in highly correlated stable multiply excited states is discussed.

Partial Wave Dispersion Relations: Application to Electron-Atom Scattering

NASA Technical Reports Server (NTRS)

Temkin, A.; Drachman, Richard J.

1999-01-01

In this Letter we propose the use of partial wave dispersion relations (DR's) as the way of solving the long-standing problem of correctly incorporating exchange in a valid DR for electron-atom scattering. In particular a method is given for effectively calculating the contribution of the discontinuity and/or poles of the partial wave amplitude which occur in the negative E plane. The method is successfully tested in three cases: (i) the analytically solvable exponential potential, (ii) the Hartree potential, and (iii) the S-wave exchange approximation for electron-hydrogen scattering.

Interaction potential between a helium atom and metal surfaces

NASA Technical Reports Server (NTRS)

Takada, Y.; Kohn, W.

1985-01-01

By employing an S-matrix theory for evanescent waves, the repulsive potential between a helium atom and corrugated metal surfaces has been calculated. P-wave interactions and intra-atomic correlation effects were found to be very important. The corrugation part of the interaction potential is much weaker than predicted by the effective-medium theory. Application to Cu, Ni, and Ag (110) surfaces gives good agreement with experiment without any adjustable parameters.

From plane waves to local Gaussians for the simulation of correlated periodic systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Booth, George H., E-mail: george.booth@kcl.ac.uk; Tsatsoulis, Theodoros; Grüneis, Andreas, E-mail: a.grueneis@fkf.mpg.de

2016-08-28

We present a simple, robust, and black-box approach to the implementation and use of local, periodic, atom-centered Gaussian basis functions within a plane wave code, in a computationally efficient manner. The procedure outlined is based on the representation of the Gaussians within a finite bandwidth by their underlying plane wave coefficients. The core region is handled within the projected augment wave framework, by pseudizing the Gaussian functions within a cutoff radius around each nucleus, smoothing the functions so that they are faithfully represented by a plane wave basis with only moderate kinetic energy cutoff. To mitigate the effects of themore » basis set superposition error and incompleteness at the mean-field level introduced by the Gaussian basis, we also propose a hybrid approach, whereby the complete occupied space is first converged within a large plane wave basis, and the Gaussian basis used to construct a complementary virtual space for the application of correlated methods. We demonstrate that these pseudized Gaussians yield compact and systematically improvable spaces with an accuracy comparable to their non-pseudized Gaussian counterparts. A key advantage of the described method is its ability to efficiently capture and describe electronic correlation effects of weakly bound and low-dimensional systems, where plane waves are not sufficiently compact or able to be truncated without unphysical artifacts. We investigate the accuracy of the pseudized Gaussians for the water dimer interaction, neon solid, and water adsorption on a LiH surface, at the level of second-order Møller–Plesset perturbation theory.« less

Roothaan-Hartree-Fock ground-state atomic wave functions: Slater-type orbital expansions and expectation values for Z = 2-54

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bunge, C.F.; Barrientos, J.A.; Bunge, A.V.

1993-01-01

Roothaan-Hartree-Fock orbitals expressed in a Slater-type basis are reported for the ground states of He through Xe. Energy accuracy ranges between 8 and 10 significant figures, reducing by between 21 and 2,770 times the energy errors of the previous such compilation (E. Clementi and C. Roetti, Atomic Data and Nuclear Data Tables 14, 177, 1974). For each atom, the total energy, kinetic energy, potential energy, virial ratio, electron density at the nucleus, and the Kato cusp are given together with radial expectation values [l angle]r[sup n][r angle] with n from [minus]3 to 2 for each orbital, orbital energies, and orbitalmore » expansion coefficients. 29 refs., 1 tab.« less

Measurements of the structure of an ionizing shock wave in a hydrogen-helium mixture

NASA Technical Reports Server (NTRS)

Leibowitz, L. P.

1972-01-01

Shock structure during ionization of a hydrogen-helium mixture was studied using hydrogen line and continuum emission measurements. A reaction scheme is proposed which includes hydrogen dissociation and a two-step excitation-ionization mechanism for hydrogen ionization by atom-atom and atom-electron collisions. Agreement was achieved between numerical calculations and measurements of emission intensity as a function of time for shock velocities from 13 to 20 km/sec in a 0.208 H2 - 0.792 He mixture. The electron temperature was found to be significantly different from the heavy particle temperature during much of the ionization process. Similar time histories for H beta and continuum emission indicate upper level populations of hydrogen in equilibrium with the electron concentration during the relaxation process.

Measurements of the structure of an ionizing shock wave in a hydrogen-helium mixture.

NASA Technical Reports Server (NTRS)

Leibowitz, L. P.

1973-01-01

Shock structure during ionization of a hydrogen-helium mixture has been followed using hydrogen line and continuum emission measurements. A reaction scheme is proposed which includes hydrogen dissociation and a two-step excitation-ionization mechanism for hydrogen ionization by atom-atom and atom-electron collisions. Agreement has been achieved between numerical calculations and measurements of emission intensity as a function of time for shock velocities from 13 to 20 km/sec in a 0.208 H2-0.792 He mixture. The electron temperature was found to be significantly different from the heavy particle temperature during much of the ionization process. Similar time histories for H beta and continuum emission indicate upper level populations of hydrogen in equilibrium with the electron concentration during the relaxation process.

Kinetic-energy matrix elements for atomic Hylleraas-CI wave functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, Frank E., E-mail: harris@qtp.ufl.edu

Hylleraas-CI is a superposition-of-configurations method in which each configuration is constructed from a Slater-type orbital (STO) product to which is appended (linearly) at most one interelectron distance r{sub ij}. Computations of the kinetic energy for atoms by this method have been difficult due to the lack of formulas expressing these matrix elements for general angular momentum in terms of overlap and potential-energy integrals. It is shown here that a strategic application of angular-momentum theory, including the use of vector spherical harmonics, enables the reduction of all atomic kinetic-energy integrals to overlap and potential-energy matrix elements. The new formulas are validatedmore » by showing that they yield correct results for a large number of integrals published by other investigators.« less

Simulated quantum computation of molecular energies.

PubMed

Aspuru-Guzik, Alán; Dutoi, Anthony D; Love, Peter J; Head-Gordon, Martin

2005-09-09

The calculation time for the energy of atoms and molecules scales exponentially with system size on a classical computer but polynomially using quantum algorithms. We demonstrate that such algorithms can be applied to problems of chemical interest using modest numbers of quantum bits. Calculations of the water and lithium hydride molecular ground-state energies have been carried out on a quantum computer simulator using a recursive phase-estimation algorithm. The recursive algorithm reduces the number of quantum bits required for the readout register from about 20 to 4. Mappings of the molecular wave function to the quantum bits are described. An adiabatic method for the preparation of a good approximate ground-state wave function is described and demonstrated for a stretched hydrogen molecule. The number of quantum bits required scales linearly with the number of basis functions, and the number of gates required grows polynomially with the number of quantum bits.

Surface phonons and elastic surface waves

NASA Astrophysics Data System (ADS)

Büscher, H.; Klein-Heßling, W.; Ludwig, W.

Theoretical investigations on the dynamics of the (001), (110) and (111) surfaces of some cubic metals (Ag, Cu, Ni) will be reviewed. Both, lattice dynamical and continuum theoretical results are obtained via a Green's function formalism. The main attitude of this paper is the comparison of our results with experiments and with results obtained via slab-calculations. The calculation of elastic surface waves has been performed using a modified surface-green-function-matching method. We have used two different approaches of calculation the bulk Green's function (a) using the spectral representation and (b) a method, what works on residues. The investigations are carried out using shortrange phenomenological potentials. The atomic force constants in the first surface layers are modified to describe surface phonon anomalies, observed by experiments. In the case of Ag (100) and Ag(110) we conclude that the detection of odd symmetry shear modes by Erskine et al. [1 a, b] was not very accurate.

Self-consistent average-atom scheme for electronic structure of hot and dense plasmas of mixture.

PubMed

Yuan, Jianmin

2002-10-01

An average-atom model is proposed to treat the electronic structures of hot and dense plasmas of mixture. It is assumed that the electron density consists of two parts. The first one is a uniform distribution with a constant value, which is equal to the electron density at the boundaries between the atoms. The second one is the total electron density minus the first constant distribution. The volume of each kind of atom is proportional to the sum of the charges of the second electron part and of the nucleus within each atomic sphere. By this way, one can make sure that electrical neutrality is satisfied within each atomic sphere. Because the integration of the electron charge within each atom needs the size of that atom in advance, the calculation is carried out in a usual self-consistent way. The occupation numbers of electron on the orbitals of each kind of atom are determined by the Fermi-Dirac distribution with the same chemical potential for all kinds of atoms. The wave functions and the orbital energies are calculated with the Dirac-Slater equations. As examples, the electronic structures of the mixture of Au and Cd, water (H2O), and CO2 at a few temperatures and densities are presented.

Phase modulation for reduced vibration sensitivity in laser-cooled clocks in space

NASA Technical Reports Server (NTRS)

Klipstein, W.; Dick, G.; Jefferts, S.; Walls, F.

2001-01-01

The standard interrogation technique in atomic beam clocks is square-wave frequency modulation (SWFM), which suffers a first order sensitivity to vibrations as changes in the transit time of the atoms translates to perceived frequency errors. Square-wave phase modulation (SWPM) interrogation eliminates sensitivity to this noise.

Developing density functional theory for Bose-Einstein condensates. The case of chemical bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putz, Mihai V., E-mail: mvputz@cbg.uvt.ro

Since the nowadays growing interest in Bose-Einstein condensates due to the expanded experimental evidence on various atomic systems within optical lattices in weak and strong coupling regimes, the connection with Density Functional Theory is firstly advanced within the mean field framework at three levels of comprehension: the many-body normalization condition, Thomas-Fermi limit, and the chemical hardness closure with the inter-bosonic strength and universal Hohenberg-Kohn functional. As an application the traditional Heitler-London quantum mechanical description of the chemical bonding for homopolar atomic systems is reloaded within the non-linear Schrödinger (Gross-Pitaevsky) Hamiltonian; the results show that a two-fold energetic solution is registeredmore » either for bonding and antibonding states, with the bosonic contribution being driven by the square of the order parameter for the Bose-Einstein condensate density in free (gas) motion, while the associate wave functions remain as in classical molecular orbital model.« less

Coherent and incoherent dipole-dipole interactions between atoms

NASA Astrophysics Data System (ADS)

Robicheaux, Francis

2016-05-01

Results will be presented on the collective interaction between atoms due to the electric dipole-dipole coupling between states of different parity on two different atoms. A canonical example of this effect is when the electronic state of one atom has S-character and the state of another atom has P-character. The energy difference between the two states plays an important role in the interaction since the change in energy determines the wave number of a photon that would cause a transition between the states. If the atoms are much closer than the wave length of this photon, then the dipole-dipole interaction is in the near field and has a 1 /r3 dependence on atomic separation. If the atoms are farther apart than the wave length, then the interaction is in the far field and has a 1 / r dependence. When many atoms interact, collective effects can dominate the system with the character of the collective effect depending on whether the atomic separation leads to near field or far field coupling. As an example of the case where the atoms are in the far field, the line broadening of transitions and strong deviations from the Beer-Lambert law in a diffuse gas will be presented. As an example of near field collective behavior, the radiative properties of a Rydberg gas will be presented. Based upon work supported by the National Science Foundation under Grant No. 1404419-PHY in collaboration with R.T. Sutherland.

a Point-Like Picture of the Hydrogen Atom

NASA Astrophysics Data System (ADS)

Faghihi, F.; Jangjoo, A.; Khani, M.

A point-like picture of the Schrödinger solution for hydrogen atom is worked to emphasize that "point-like particles" may describe as "probability wave function". In each case, the three-dimensional shape of the |Ψnlm(rn, cosθ)|2 is plotted and the paths of the point-like electron (it is better to say reduced mass of the pair particles) are described in each closed shell. Finally, the orbital shape of the molecules are given according to the present simple model. In our opinion, "interpretations of the Correspondence Principle", which is a basic principle in all elementary quantum text, seems to be reviewed again!

Endo-Fullerene and Doped Diamond Nanocrystallite Based Models of Qubits for Solid-State Quantum Computers

NASA Technical Reports Server (NTRS)

Park, Seongjun; Srivastava, Deepak; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)

2001-01-01

Models of encapsulated 1/2 nuclear spin H-1 and P-31 atoms in fullerene and diamond nanocrystallite, respectively, are proposed and examined with ab-initio local density functional method for possible applications as single quantum bits (qubits) in solid-state quantum computers. A H-1 atom encapsulated in a fully deuterated fullerene, C(sub 20)D(sub 20), forms the first model system and ab-initio calculation shows that H-1 atom is stable in atomic state at the center of the fullerene with a barrier of about 1 eV to escape. A P-31 atom positioned at the center of a diamond nanocrystallite is the second model system, and 3 1P atom is found to be stable at the substitutional site relative to interstitial sites by 15 eV, Vacancy formation energy is 6 eV in diamond so that substitutional P-31 atom will be stable against diffusion during the formation mechanisms within the nanocrystallite. The coupling between the nuclear spin and weakly bound (valance) donor electron coupling in both systems is found to be suitable for single qubit applications, where as the spatial distributions of (valance) donor electron wave functions are found to be preferentially spread along certain lattice directions facilitating two or more qubit applications. The feasibility of the fabrication pathways for both model solid-state qubit systems within practical quantum computers is discussed with in the context of our proposed solid-state qubits.

Role of the phase-matching condition in nondegenerate four-wave mixing in hot vapors for the generation of squeezed states of light

NASA Astrophysics Data System (ADS)

Turnbull, M. T.; Petrov, P. G.; Embrey, C. S.; Marino, A. M.; Boyer, V.

2013-09-01

Nondegenerate forward four-wave mixing in hot atomic vapors has been shown to produce strong quantum correlations between twin beams of light [McCormick , Opt. Lett.OPLEDP0146-959210.1364/OL.32.000178 32, 178 (2007)], in a configuration which minimizes losses by absorption. In this paper, we look at the role of the phase-matching condition in the trade-off that occurs between the efficiency of the nonlinear process and the absorption of the twin beams. To this effect, we develop a semiclassical model by deriving the atomic susceptibilities in the relevant double-Λ configuration and by solving the classical propagation of the twin-beam fields for parameters close to those found in typical experiments. These theoretical results are confirmed by a simple experimental study of the nonlinear gain experienced by the twin beams as a function of the phase mismatch. The model shows that the amount of phase mismatch is key to the realization of the physical conditions in which the absorption of the twin beams is minimized while the cross coupling between the twin beams is maintained at the level required for the generation of strong quantum correlations. The optimum is reached when the four-wave mixing process is not phase matched for fully resonant four-wave mixing.

Atomic Gravitational Wave Interferometric Sensors (AGIS) in Space

NASA Astrophysics Data System (ADS)

Sugarbaker, Alex; Hogan, Jason; Johnson, David; Dickerson, Susannah; Kovachy, Tim; Chiow, Sheng-Wey; Kasevich, Mark

2012-06-01

Atom interferometers have the potential to make sensitive gravitational wave detectors, which would reinforce our fundamental understanding of gravity and provide a new means of observing the universe. We focus here on the AGIS-LEO proposal [1]. Gravitational waves can be observed by comparing a pair of atom interferometers separated over an extended baseline. The mission would offer a strain sensitivity that would provide access to a rich scientific region with substantial discovery potential. This band is not currently addressed with the LIGO or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Many of the techniques relevant to an AGIS mission can be investigated in the Stanford 10-m drop tower.[4pt] [1] J.M. Hogan, et al., Gen. Rel. Grav. 43, 1953-2009 (2011).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Peng; Department of Physics, Renmin University of China, Beijing 100872; Naidon, Pascal

Most of the current theories on the p-wave superfluid in cold atomic gases are based on the effective-range theory for the two-body scattering, where the low-energy p-wave scattering amplitude f{sub 1}(k) is given by f{sub 1}(k)=-1/[ik+1/(Vk{sup 2})+1/R]. Here k is the incident momentum, V and R are the k-independent scattering volume and effective range, respectively. However, due to the long-range nature of the van der Waals interaction between two colliding ultracold atoms, the p-wave scattering amplitude of the two atoms is not described by the effective-range theory [J. Math. Phys. 4, 54 (1963); Phys. Rev. A 58, 4222 (1998)]. Inmore » this paper we provide an explicit calculation for the p-wave scattering of two ultracold atoms near the p-wave magnetic Feshbach resonance. We show that in this case the low-energy p-wave scattering amplitude f{sub 1}(k)=-1/[ik+1/(V{sup eff}k{sup 2})+1/(S{sup eff}k)+1/R{sup eff}] where V{sup eff}, S{sup eff}, and R{sup eff} are k-dependent parameters. Based on this result, we identify sufficient conditions for the effective-range theory to be a good approximation of the exact scattering amplitude. Using these conditions we show that the effective-range theory is a good approximation for the p-wave scattering in the ultracold gases of {sup 6}Li and {sup 40}K when the scattering volume is enhanced by the resonance.« less

Charge density wave order in 1D mirror twin boundaries of single-layer MoSe 2

DOE PAGES

Barja, Sara; Wickenburg, Sebastian; Liu, Zhen-Fei; ...

2016-04-18

Here, We provide direct evidence for the existence of isolated, one-dimensional charge density waves at mirror twin boundaries (MTBs) of single-layer semiconducting MoSe 2. Such MTBs have been previously observed by transmission electron microscopy and have been predicted to be metallic in MoSe 2 and MoS 2. Our low-temperature scanning tunnelling microscopy/spectroscopy measurements revealed a substantial bandgap of 100 meV opening at the Fermi energy in the otherwise metallic one-dimensional structures. We found a periodic modulation in the density of states along the MTB, with a wavelength of approximately three lattice constants. In addition to mapping the energy-dependent densitymore » of states, we determined the atomic structure and bonding of the MTB through simultaneous high-resolution non-contact atomic force microscopy. Density functional theory calculations based on the observed structure reproduced both the gap opening and the spatially resolved density of states.« less

An optimized full-configuration-interaction nuclear orbital approach to a ``hard-core'' interaction problem: Application to (3He)N-Cl2(B) clusters (N<=4)

NASA Astrophysics Data System (ADS)

de Lara-Castells, M. P.; Villarreal, P.; Delgado-Barrio, G.; Mitrushchenkov, A. O.

2009-11-01

An efficient full-configuration-interaction nuclear orbital treatment has been recently developed as a benchmark quantum-chemistry-like method to calculate ground and excited "solvent" energies and wave functions in small doped ΔEest clusters (N ≤4) [M. P. de Lara-Castells, G. Delgado-Barrio, P. Villarreal, and A. O. Mitrushchenkov, J. Chem. Phys. 125, 221101 (2006)]. Additional methodological and computational details of the implementation, which uses an iterative Jacobi-Davidson diagonalization algorithm to properly address the inherent "hard-core" He-He interaction problem, are described here. The convergence of total energies, average pair He-He interaction energies, and relevant one- and two-body properties upon increasing the angular part of the one-particle basis set (expanded in spherical harmonics) has been analyzed, considering Cl2 as the dopant and a semiempirical model (T-shaped) He-Cl2(B) potential. Converged results are used to analyze global energetic and structural aspects as well as the configuration makeup of the wave functions, associated with the ground and low-lying "solvent" excited states. Our study reveals that besides the fermionic nature of H3e atoms, key roles in determining total binding energies and wave-function structures are played by the strong repulsive core of the He-He potential as well as its very weak attractive region, the most stable arrangement somehow departing from the one of N He atoms equally spaced on equatorial "ring" around the dopant. The present results for N =4 fermions indicates the structural "pairing" of two H3e atoms at opposite sides on a broad "belt" around the dopant, executing a sort of asymmetric umbrella motion. This pairing is a compromise between maximizing the H3e-H3e and the He-dopant attractions, and suppressing at the same time the "hard-core" repulsion. Although the He-He attractive interaction is rather weak, its contribution to the total energy is found to scale as a power of three and it thus increasingly affects the pair density distributions as the cluster grows in size.

The influence of velocity-changing collisions on resonant degenerate four-wave mixing

NASA Technical Reports Server (NTRS)

Richardson, W. H.; Maleki, L.; Garmire, Elsa

1989-01-01

The phase-conjugate signal observed in resonant degenerate four-wave mixing on the 6 3P2 to 7 3S1 transition of atomic Hg in an Hg-Ar discharge is investigated. At a fixed Ar pressure the variation of the signal with pump powers is explained by a model that includes the effects of velocity-changing collisions (VCCs). As the Ar pressure was varied from 0 to 1 torr, an increase in the phase-conjugate signal was observed and is ascribed to a change in the discharge dynamics with Ar pressure and to the influence of VCCs. To further clarify the role of collisions and optical pumping, degenerate four-wave mixing spectra are examined as a function of pump power. Line shapes are briefly discussed.

Coherent storage of temporally multimode light using a spin-wave atomic frequency comb memory

NASA Astrophysics Data System (ADS)

Gündoǧan, M.; Mazzera, M.; Ledingham, P. M.; Cristiani, M.; de Riedmatten, H.

2013-04-01

We report on the coherent and multi-temporal mode storage of light using the full atomic frequency comb memory scheme. The scheme involves the transfer of optical atomic excitations in Pr3+:Y2SiO5 to spin waves in hyperfine levels using strong single-frequency transfer pulses. Using this scheme, a total of five temporal modes are stored and recalled on-demand from the memory. The coherence of the storage and retrieval is characterized using a time-bin interference measurement resulting in visibilities higher than 80%, independent of the storage time. This coherent and multimode spin-wave memory is promising as a quantum memory for light.

Comparing Laser Interferometry and Atom Interferometry Approaches to Space-Based Gravitational-Wave Measurement

NASA Technical Reports Server (NTRS)

Baker, John; Thorpe, Ira

2012-01-01

Thoroughly studied classic space-based gravitational-wave missions concepts such as the Laser Interferometer Space Antenna (LISA) are based on laser-interferometry techniques. Ongoing developments in atom-interferometry techniques have spurred recently proposed alternative mission concepts. These different approaches can be understood on a common footing. We present an comparative analysis of how each type of instrument responds to some of the noise sources which may limiting gravitational-wave mission concepts. Sensitivity to laser frequency instability is essentially the same for either approach. Spacecraft acceleration reference stability sensitivities are different, allowing smaller spacecraft separations in the atom interferometry approach, but acceleration noise requirements are nonetheless similar. Each approach has distinct additional measurement noise issues.

Gauge symmetry, chirality and parity effects in four-particle systems: Coulomb's law as a universal function for diatomic molecules.

PubMed

Van Hooydonk, G

2000-11-01

Following recent work in search for a universal function (Van Hooydonk, Eur. J. Inorg. Chem., (1999), 1617), we test four symmetric +/- a(n)Rn potentials for reproducing molecular potential energy curves (PECs). Classical gauge symmetry for 1/R-potentials results in generic left right asymmetric PECs. A pair of symmetric perturbed Coulomb potentials is quantitatively in accordance with observed PECs. For a bond, a four-particle system, charge inversion (a parity effect, atom chirality) is the key to explain this shape generically. A parity adapted Hamiltonian reduces from ten to two terms and to a soluble Bohr-like formula, a Kratzer (1 - Re/R)2 potential. The result is similar to the combined action of spin and wave function symmetry upon the Hamiltonian in Heitler-London theory. Analytical perturbed Coulomb functions varying with (1 - Re/R) scale attractive and repulsive branches of PECs for 13 bonds H2, HF, LiH, KH, AuH, Li2, LiF, KLi, NaCs, Rb2, RbCs, Cs2 and I2 in a single straight line. The 400 turning points for 13 bonds are reproduced with a deviation of 0.007 A at both branches. For 230 points at the repulsive side, the deviation is 0.003 A. The perturbed electrostatic Coulomb law is a universal molecular function. Ab initio zero molecular parameter functions give PECs of acceptable quality, just using atomic ionisation energies. The function can be used as a model potential for inverting levels and gives a first principle's comparison of short- and long-range interactions, important for the study of cold atoms. Wave-packet dynamics, femto-chemistry applied to the crossing of covalent and ionic curves, can provide evidence for this theory. We anticipate this scale/shape invariant scheme applies to smaller scales in nuclear and high-energy particle physics. For larger gravitational scales (Newton 1/R potentials), problems with super-unification are discussed. Reactions between hydrogen and antihydrogen, feasible in the near future, will probably produce normal H2.

Plane-Wave Implementation and Performance of à-la-Carte Coulomb-Attenuated Exchange-Correlation Functionals for Predicting Optical Excitation Energies in Some Notorious Cases.

PubMed

Bircher, Martin P; Rothlisberger, Ursula

2018-06-12

Linear-response time-dependent density functional theory (LR-TD-DFT) has become a valuable tool in the calculation of excited states of molecules of various sizes. However, standard generalized-gradient approximation and hybrid exchange-correlation (xc) functionals often fail to correctly predict charge-transfer (CT) excitations with low orbital overlap, thus limiting the scope of the method. The Coulomb-attenuation method (CAM) in the form of the CAM-B3LYP functional has been shown to reliably remedy this problem in many CT systems, making accurate predictions possible. However, in spite of a rather consistent performance across different orbital overlap regimes, some pitfalls remain. Here, we present a fully flexible and adaptable implementation of the CAM for Γ-point calculations within the plane-wave pseudopotential molecular dynamics package CPMD and explore how customized xc functionals can improve the optical spectra of some notorious cases. We find that results obtained using plane waves agree well with those from all-electron calculations employing atom-centered bases, and that it is possible to construct a new Coulomb-attenuated xc functional based on simple considerations. We show that such a functional is able to outperform CAM-B3LYP in some cases, while retaining similar accuracy in systems where CAM-B3LYP performs well.

Continuous wave cavity ring-down spectroscopy for velocity distribution measurements in plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCarren, D.; Lockheed Martin, Palmdale, California 93599; Scime, E., E-mail: earl.scime@mail.wvu.edu

2015-10-15

We report the development of a continuous wave cavity ring-down spectroscopic (CW-CRDS) diagnostic for real-time, in situ measurement of velocity distribution functions of ions and neutral atoms in plasma. This apparatus is less complex than conventional CW-CRDS systems. We provide a detailed description of the CW-CRDS apparatus as well as measurements of argon ions and neutrals in a high-density (10{sup 9} cm{sup −3} < plasma density <10{sup 13} cm{sup −3}) plasma. The CW-CRDS measurements are validated through comparison with laser induced fluorescence measurements of the same absorbing states of the ions and neutrals.

MB3a Infrasound Sensor Evaluation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merchant, Bion J.; McDowell, Kyle D.

2014-11-01

Sandia National Laboratories has tested and evaluated a new infrasound sensor, the MB3a, manufactured by Seismo Wave. These infrasound sensors measure pressure output by a methodology developed by researchers at the French Alternative Energies and Atomic Energy Commission (CEA) and the technology was recently licensed to Seismo Wave for production and sales. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, transfer function, power, self-noise, dynamic range, seismic sensitivity, and self- calibration ability. The MB3a infrasound sensors are being evaluated for potential use in the International Monitoring System (IMS) of the Comprehensive Nuclear Test-Ban-Treaty Organization (CTBTO).

On the bosonic atoms

NASA Astrophysics Data System (ADS)

Amusia, M. Ya.; Chernysheva, L. V.

2018-01-01

We investigate ground state properties of atoms, in which substitute fermions - electrons by bosons, namely π --mesons. We perform some calculations in the frame of modified Hartree-Fock (HF) equation. The modification takes into account symmetry, instead of anti-symmetry of the pair identical bosons wave function. The modified HF approach thus enhances (doubles) the effect of self-action for the boson case. Therefore, we accordingly modify the HF equations by eliminating the self-action terms "by hand". The contribution of meson-meson and meson-nucleon non-Coulomb interaction is inessential at least for atoms with low and intermediate nuclear charge, which is our main subject. We found that the binding energy of pion negative ions A π - , pion atoms A π , and the number of extra bound pions ΔN π increases with the growth of nuclear charge Z. For e.g. Xe ΔN π = 4. As an example of a simple process with a pion atom, we consider photoionization that differs essentially from that for electron atoms. Namely, it is not monotonic decreasing from the threshold but has instead a prominent maximum above threshold. We study also elastic scattering of pions by pion atoms.

Strong influence of off-site symmetry positions of hydrogen atoms in ScH3 hcp phases

NASA Astrophysics Data System (ADS)

Pakornchote, T.; Bovornratanaraks, T.; Vannarat, S.; Pinsook, U.

2016-01-01

We investigate the wave-like arrangements of H atoms around metal plane (Hm) in the ScH3 hcp phase by using the ab-initio method. We found that only P63 / mmc, P 3 bar c 1, P63cm and P63 phases are energetically favorable. The wave-like arrangement allows the off-site symmetry positions of the H atoms, and leads to substantial changes in the pair distribution between Sc and H atoms which are associating with the changes in the electronic structure in such a way that the total energy is lowering. The symmetry breaking from P63mmc is also responsible for the band gap opening. In the P63 structure, the calculated band gap is 0.823 eV and 1.223 eV using GGA and sX-LDA functionals, respectively. This band gap can be compared with 1.7 eV derived from the optical measurement and 1.55 eV from the HSE06 calculation. Thus, the broken symmetry structures can be viewed as Peierls distortion of the P63 / mmc structure. Furthermore, we found that only the P63 structure is dynamically stable, unlike YH3 where the P63cm structure is also stable. The stability of P63 comes from sufficiently strong interactions between two neighboring H atoms at their off-site symmetry positions, i.e. near the metal plane and near the tetragonal site. The P63 phonon density of states is in good agreement with the data from the neutron experiment.

Solving the Quantum Many-Body Problem via Correlations Measured with a Momentum Microscope

NASA Astrophysics Data System (ADS)

Hodgman, S. S.; Khakimov, R. I.; Lewis-Swan, R. J.; Truscott, A. G.; Kheruntsyan, K. V.

2017-06-01

In quantum many-body theory, all physical observables are described in terms of correlation functions between particle creation or annihilation operators. Measurement of such correlation functions can therefore be regarded as an operational solution to the quantum many-body problem. Here, we demonstrate this paradigm by measuring multiparticle momentum correlations up to third order between ultracold helium atoms in an s -wave scattering halo of colliding Bose-Einstein condensates, using a quantum many-body momentum microscope. Our measurements allow us to extract a key building block of all higher-order correlations in this system—the pairing field amplitude. In addition, we demonstrate a record violation of the classical Cauchy-Schwarz inequality for correlated atom pairs and triples. Measuring multiparticle momentum correlations could provide new insights into effects such as unconventional superconductivity and many-body localization.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Gyeong Won; Shim, Jaewon; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

The influence of renormalization plasma screening on the entanglement fidelity for the elastic electron-atom scattering is investigated in partially ionized dense hydrogen plasmas. The partial wave analysis and effective interaction potential are employed to obtain the scattering entanglement fidelity in dense hydrogen plasmas as functions of the collision energy, the Debye length, and the renormalization parameter. It is found that the renormalization plasma shielding enhances the scattering entanglement fidelity. Hence, we show that the transmission of the quantum information can be increased about 10% due to the renormalization shielding effect in dense hydrogen plasmas. It is also found that themore » renormalization shielding effect on the entanglement fidelity for the electron-atom collision increases with an increase of the collision energy. In addition, the renormalization shielding function increases with increasing collision energy and saturates to the unity with an increase of the Debye length.« less

Application of P-wave hybrid theory to the scattering of electrons from He+ and resonances in He and H-

NASA Astrophysics Data System (ADS)

Bhatia, A. K.

2012-09-01

The P-wave hybrid theory of electron-hydrogen elastic scattering [Bhatia, Phys. Rev. A10.1103/PhysRevA.85.052708 85, 052708 (2012)] is applied to the P-wave scattering from He ion. In this method, both short-range and long-range correlations are included in the Schrödinger equation at the same time, by using a combination of a modified method of polarized orbitals and the optical potential formalism. The short-range-correlation functions are of Hylleraas type. It is found that the phase shifts are not significantly affected by the modification of the target function by a method similar to the method of polarized orbitals and they are close to the phase shifts calculated earlier by Bhatia [Phys. Rev. A10.1103/PhysRevA.69.032714 69, 032714 (2004)]. This indicates that the correlation function is general enough to include the target distortion (polarization) in the presence of the incident electron. The important fact is that in the present calculation, to obtain similar results only a 20-term correlation function is needed in the wave function compared to the 220-term wave function required in the above-mentioned calculation. Results for the phase shifts, obtained in the present hybrid formalism, are rigorous lower bounds to the exact phase shifts. The lowest P-wave resonances in He atom and hydrogen ion have also been calculated and compared with the results obtained using the Feshbach projection operator formalism [Bhatia and Temkin, Phys. Rev. A10.1103/PhysRevA.11.2018 11, 2018 (1975)] and also with the results of other calculations. It is concluded that accurate resonance parameters can be obtained by the present method, which has the advantage of including corrections due to neighboring resonances, bound states, and the continuum in which these resonances are embedded.

Localization of atomic excitation beyond the diffraction limit using electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Miles, J. A.; Das, Diptaranjan; Simmons, Z. J.; Yavuz, D. D.

2015-09-01

We experimentally demonstrate the localization of excitation between hyperfine ground states of 87Rb atoms to as small as λ /13 -wide spatial regions. We use ultracold atoms trapped in a dipole trap and utilize electromagnetically induced transparency (EIT) for the atomic excitation. The localization is achieved by combining a spatially varying coupling laser (standing wave) with the intensity dependence of EIT. The excitation is fast (150 ns laser pulses) and the dark-state fidelity can be made higher than 94% throughout the standing wave. Because the width of the localized regions is much smaller than the wavelength of the driving light, traditional optical imaging techniques cannot resolve the localized features. Therefore, to measure the excitation profile, we use an autocorrelation-like method where we perform two EIT sequences separated by a time delay, during which we move the standing wave.

Ultra-bright pulsed electron beam with low longitudinal emittance

DOEpatents

Zolotorev, Max

2010-07-13

A high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography has been described. The source makes use of Cs atoms in an atomic beam. The source is cycled beginning with a laser pulse that excites a single Cs atom on average to a band of high-lying Rydberg nP states. The resulting valence electron Rydberg wave packet evolves in a nearly classical Kepler orbit. When the electron reaches apogee, an electric field pulse is applied that ionizes the atom and accelerates the electron away from its parent ion. The collection of electron wave packets thus generated in a series of cycles can occupy a phase volume near the quantum limit and it can possess very high brightness. Each wave packet can exhibit a considerable degree of coherence.

Veselago lensing with ultracold atoms in an optical lattice.

PubMed

Leder, Martin; Grossert, Christopher; Weitz, Martin

2014-01-01

Veselago pointed out that electromagnetic wave theory allows for materials with a negative index of refraction, in which most known optical phenomena would be reversed. A slab of such a material can focus light by negative refraction, an imaging technique strikingly different from conventional positive refractive index optics, where curved surfaces bend the rays to form an image of an object. Here we demonstrate Veselago lensing for matter waves, using ultracold atoms in an optical lattice. A relativistic, that is, photon-like, dispersion relation for rubidium atoms is realized with a bichromatic optical lattice potential. We rely on a Raman π-pulse technique to transfer atoms between two different branches of the dispersion relation, resulting in a focusing that is completely analogous to the effect described by Veselago for light waves. Future prospects of the demonstrated effects include novel sub-de Broglie wavelength imaging applications.

Correspondence: Reply to ‘Phantom phonon localization in relaxors’

DOE PAGES

Manley, Michael E.; Abernathy, Douglas L.; Budai, John D.

2017-12-05

The Correspondence by Gehring et al. mistakes Anderson phonon localization for the concept of an atomic-scale local mode. An atomic-scale local mode refers to a single atom vibrating on its own within a crystal. Such a local mode will have an almost flat intensity profile, but this is not the same as phonon localization. Anderson localization is a wave interference effect in a disordered system that results in waves becoming spatially localized. The length scale of the localized waves is set by the wavelength, which is approximately 2 nm in this case. This larger length scale in real space meansmore » narrower intensity profiles in reciprocal space. Here, we conclude that the claims in the Correspondence by Gehring et al. are incorrect because they mistakenly assume that the length scale for Anderson localization is atomic, and because the experimental observations rule out multiple scattering as the origin.« less

Correspondence: Reply to ‘Phantom phonon localization in relaxors’

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manley, Michael E.; Abernathy, Douglas L.; Budai, John D.

The Correspondence by Gehring et al. mistakes Anderson phonon localization for the concept of an atomic-scale local mode. An atomic-scale local mode refers to a single atom vibrating on its own within a crystal. Such a local mode will have an almost flat intensity profile, but this is not the same as phonon localization. Anderson localization is a wave interference effect in a disordered system that results in waves becoming spatially localized. The length scale of the localized waves is set by the wavelength, which is approximately 2 nm in this case. This larger length scale in real space meansmore » narrower intensity profiles in reciprocal space. Here, we conclude that the claims in the Correspondence by Gehring et al. are incorrect because they mistakenly assume that the length scale for Anderson localization is atomic, and because the experimental observations rule out multiple scattering as the origin.« less

Ten reasons why a thermalized system cannot be described by a many-particle wave function

NASA Astrophysics Data System (ADS)

Drossel, Barbara

2017-05-01

It is widely believed that the underlying reality behind statistical mechanics is a deterministic and unitary time evolution of a many-particle wave function, even though this is in conflict with the irreversible, stochastic nature of statistical mechanics. The usual attempts to resolve this conflict for instance by appealing to decoherence or eigenstate thermalization are riddled with problems. This paper considers theoretical physics of thermalized systems as it is done in practice and shows that all approaches to thermalized systems presuppose in some form limits to linear superposition and deterministic time evolution. These considerations include, among others, the classical limit, extensivity, the concepts of entropy and equilibrium, and symmetry breaking in phase transitions and quantum measurement. As a conclusion, the paper suggests that the irreversibility and stochasticity of statistical mechanics should be taken as a real property of nature. It follows that a gas of a macroscopic number N of atoms in thermal equilibrium is best represented by a collection of N wave packets of a size of the order of the thermal de Broglie wave length, which behave quantum mechanically below this scale but classically sufficiently far beyond this scale. In particular, these wave packets must localize again after scattering events, which requires stochasticity and indicates a connection to the measurement process.

Mach-Zehnder atom interferometer inside an optical fiber

NASA Astrophysics Data System (ADS)

Xin, Mingjie; Leong, Wuiseng; Chen, Zilong; Lan, Shau-Yu

2017-04-01

Precision measurement with light-pulse grating atom interferometry in free space have been used in the study of fundamental physics and applications in inertial sensing. Recent development of photonic band-gap fibers allows light for traveling in hollow region while preserving its fundamental Gaussian mode. The fibers could provide a very promising platform to transfer cold atoms. Optically guided matter waves inside a hollow-core photonic band-gap fiber can mitigate diffraction limit problem and has the potential to bring research in the field of atomic sensing and precision measurement to the next level of compactness and accuracy. Here, we will show our experimental progress towards an atom interferometer in optical fibers. We designed an atom trapping scheme inside a hollow-core photonic band-gap fiber to create an optical guided matter waves system, and studied the coherence properties of Rubidium atoms in this optical guided system. We also demonstrate a Mach-Zehnder atom interferometer in the optical waveguide. This interferometer is promising for precision measurements and designs of mobile atomic sensors.

Ultra-sensitive inertial sensors via neutral-atom interferometry

NASA Technical Reports Server (NTRS)

Clauser, John F.

1989-01-01

Upon looking at the various colossal interferometers, etc., discussed at this conference to test gravitational theory, one cannot avoid feeling that easier approaches exist. The use of low velocity, neutral atom matter waves in place of electromagnetic waves in sensitive inertial interferometer configurations is proposed. For applications, spacecraft experiments to sense a drag-free condition, to measure the Lense-Thirring precession, to measure the gravitomagnetic effect and/or the earth's geopotential (depending on altitude), and to detect long period gravitational waves are considered. Also, a terrestrial precision test of the equivalence principle on spin polarized atoms, capable of detecting effects of the 5th force is considered. While the ideas described herein are preliminary, the orders of magnitude are sufficiently tantalizing to warrant further study. Although existing proposed designs may be adequate for some of these experiments, the use of matter-wave interferometry offers reduced complexity and cost, and an absence of cryogenics.

Consistent calculation of the screening and exchange effects in allowed β- transitions

NASA Astrophysics Data System (ADS)

Mougeot, X.; Bisch, C.

2014-07-01

The atomic exchange effect has previously been demonstrated to have a great influence at low energy on the Pu241 β- transition. The screening effect has been given as a possible explanation for a remaining discrepancy. Improved calculations have been made to consistently evaluate these two atomic effects, compared here to the recent high-precision measurements of Pu241 and Ni63 β spectra. In this paper a screening correction has been defined to account for the spatial extension of the electron wave functions. Excellent overall agreement of about 1% from 500 eV to the end-point energy has been obtained for both β spectra, which demonstrates that a rather simple β decay model for allowed transitions, including atomic effects within an independent-particle model, is sufficient to describe well the current most precise measurements.

DFT STUDY OF CO AND NO ADSORPTION ON BORON NITRIDE (BN)n = 3 - 5 NANOCLUSTERS

NASA Astrophysics Data System (ADS)

Zahedi, Ehsan; Pangh, Abdolhakim; Ghorbanpour, Hamed

2015-11-01

Interaction of CO and NO molecules by different orientations on (BN)n=3-5 clusters have been studied at the B3LYP/6-311+G* level of theory. Total electronic energies have been corrected for geometrical counterpoise (gCP) and dispersion (D3) energies at the B3LYP/6-31G* level. Formation of a new sigma bond between the gas and (BN)3 cluster, atom in molecules (AIM) results, density of states spectrums (DOS), molecular electrostatic potential (MEP) surfaces, and visualization of wave function of molecular orbitals in the nearest bonding regions to the Fermi level have confirmed that adsorption of CO by carbon end atom, and NO by nitrogen end atom is covalent in nature, so that the charge transfer is occurred from gas molecule to the cluster.

Localization of holes near charged defects in orbitally degenerate, doped Mott insulators

NASA Astrophysics Data System (ADS)

Avella, Adolfo; Oleś, Andrzej M.; Horsch, Peter

2018-05-01

We study the role of charged defects, disorder and electron-electron (e-e) interactions in a multiband model for t2g electrons in vanadium perovskites R1-xCaxVO3 (R = La,…,Y). By means of unrestricted Hartree-Fock calculations, we find that the atomic multiplet structure persists up to 50% Ca doping. Using the inverse participation number, we explore the degree of localization and its doping dependence for all electronic states. The observation of strongly localized wave functions is consistent with our conjecture that doped holes form spin-orbital polarons that are strongly bound to the charged Ca2+ defects. Interestingly, the long-range e-e interactions lead to a discontinuity in the wave function size across the chemical potential, where the electron removal states are more localized than the addition states.

Photon scattering cross sections of H2 and He measured with synchrotron radiation

NASA Technical Reports Server (NTRS)

Ice, G. E.

1977-01-01

Total (elastic + inelastic) differential photon scattering cross sections have been measured for H2 gas and He, using an X-ray beam. Absolute measured cross sections agree with theory within the probable errors. Relative cross sections (normalized to theory at large S) agree to better than one percent with theoretical values calculated from wave functions that include the effect of electron-electron Coulomb correlation, but the data deviate significantly from theoretical independent-particle (e.g., Hartree-Fock) results. The ratios of measured absolute He cross sections to those of H2, at any given S, also agree to better than one percent with theoretical He-to-H2 cross-section ratios computed from correlated wave functions. It appears that photon scattering constitutes a very promising tool for probing electron correlation in light atoms and molecules.

Optical Measurements of Strong Radio-Frequency Fields Using Rydberg Atoms

NASA Astrophysics Data System (ADS)

Miller, Stephanie Anne

There has recently been an initiative toward establishing atomic measurement standards for field quantities, including radio-frequency, millimeter-wave, and micro-wave electric fields. Current measurement standards are obtained using dipole antennas, which are fundamentally limited in frequency bandwidth (set by the physical size of the antenna) and accuracy (due to the metal perturbing the field during the measurement). Establishing an atomic standard rectifies these problems. My thesis work contributes to an ongoing effort towards establishing the viability of using Rydberg electromagnetically induced transparency (EIT) to perform atom-based measurements of radio-frequency (RF) fields over a wide range of frequencies and field strengths, focusing on strong-field measurements. Rydberg atoms are atoms with an electron excited to a high principal quantum number, resulting in a high sensitivity to an applied field. A model based on Floquet theory is implemented to accurately describe the observed atomic energy level shifts from which information about the field is extracted. Additionally, the effects due to the different electric field domains within the measurement volume are accurately modeled. Absolute atomic measurements of fields up to 296 V/m within a +/-0.35% relative uncertainty are demonstrated. This is the strongest field measured at the time of data publication. Moreover, the uncertainty is over an order of magnitude better than that of current standards. A vacuum chamber setup that I implemented during my graduate studies is presented and its unique components are detailed. In this chamber, cold-atom samples are generated and Rydberg atoms are optically excited within the ground-state sample. The Rydberg ion detection and imaging procedure are discussed, particularly the high magnification that the system provides. By analyzing the position of the ions, the spatial correlation g(2) (r) of Rydberg-atom distributions can be extracted. Aside from ion detection, EIT is implemented in the cold-atom samples. By measuring the timing of the probe photons exiting the EIT medium, the temporal correlation function g(2)(tau) can be extracted, yielding information about the timing between two different arbitrary photons. An experimental goal using this setup is to look at g(2)(tau) in conjunction with g(2)(r) for Rydberg atoms. Progress and preliminary measurements of ion detection and EIT spectra are presented including observed qualitative behaviors.

High-temperature atomic superfluidity in lattice Bose-Fermi mixtures.

PubMed

Illuminati, Fabrizio; Albus, Alexander

2004-08-27

We consider atomic Bose-Fermi mixtures in optical lattices and study the superfluidity of fermionic atoms due to s-wave pairing induced by boson-fermion interactions. We prove that the induced fermion-fermion coupling is always attractive if the boson-boson on-site interaction is repulsive, and predict the existence of an enhanced BEC-BCS crossover as the strength of the lattice potential is varied. We show that for direct on-site fermion-fermion repulsion, the induced attraction can give rise to superfluidity via s-wave pairing at striking variance with the case of pure systems of fermionic atoms with direct repulsive interactions.

Cold Rydberg molecules

NASA Astrophysics Data System (ADS)

Raithel, Georg

2017-04-01

Cold atomic systems have opened new frontiers in atomic and molecular physics, including several types of Rydberg molecules. Three types will be reviewed. Long-range Rydberg-ground molecules, first predicted in and observed in, are formed via low-energy electron scattering of the Rydberg electron from a ground-state atom within the Rydberg atom's volume. The binding mostly arises from S- and P-wave triplet scattering. We use a Fermi model that includes S-wave and P-wave singlet and triplet scattering, the fine structure coupling of the Rydberg atom and the hyperfine structure coupling of the 5S1/2 atom (in rubidium). The hyperfine structure gives rise to mixed singlet-triplet potentials for both low-L and high-L Rydberg molecules. A classification into Hund's cases will be discussed. The talk further includes results on adiabatic potentials and adiabatic states of Rydberg-Rydberg molecules in Rb and Cs. These molecules, which have even larger bonding length than Rydberg-ground molecules, are formed via electrostatic multipole interactions. The leading interaction of neutral Rydberg-Rydberg molecules is dipole-dipole, while for ionic Rydberg molecules it is dipole-monopole. Higher-order terms are discussed. FUNDING: NSF (PHY-1506093), NNSF of China (61475123).

SU(3) Orbital Kondo Effect with Ultracold Atoms

NASA Astrophysics Data System (ADS)

Nishida, Yusuke

2013-09-01

We propose a simple but novel scheme to realize the Kondo effect with ultracold atoms. Our system consists of a Fermi sea of spinless fermions interacting with an impurity atom of different species which is confined by an isotropic potential. The interspecies attraction can be tuned with an s-wave Feshbach resonance so that the impurity atom and a spinless fermion form a bound dimer that occupies a threefold-degenerate p orbital of the confinement potential. Many-body scatterings of this dimer and surrounding spinless fermions occur with exchanging their angular momenta and thus exhibit the SU(3) orbital Kondo effect. The associated Kondo temperature has a universal leading exponent given by TK∝exp⁡[-π/(3apkF3)] that depends only on an effective p-wave scattering volume ap and a Fermi wave vector kF. We also elucidate a Kondo singlet formation at zero temperature and an anisotropic interdimer interaction mediated by surrounding spinless fermions. The Kondo effect thus realized in ultracold atom experiments may be observed as an increasing atom loss by lowering the temperature or with radio-frequency spectroscopy. Our scheme and its extension to a dense Kondo lattice will be useful to develop new insights into yet unresolved aspects of Kondo physics.

Generalized pseudopotential approach for electron-atom scattering.

NASA Technical Reports Server (NTRS)

Zarlingo, D. G.; Ishihara, T.; Poe, R. T.

1972-01-01

A generalized many-electron pseudopotential approach is presented for electron-neutral-atom scattering problems. A calculation based on this formulation is carried out for the singlet s-wave and p-wave electron-hydrogen phase shifts with excellent results. We compare the method with other approaches as well as discuss its applications for inelastic and rearrangement collision problems.

Application of the dual-kinetic-balance sets in the relativistic many-body problem of atomic structure

NASA Astrophysics Data System (ADS)

Beloy, Kyle; Derevianko, Andrei

2008-09-01

The dual-kinetic-balance (DKB) finite basis set method for solving the Dirac equation for hydrogen-like ions [V.M. Shabaev et al., Phys. Rev. Lett. 93 (2004) 130405] is extended to problems with a non-local spherically-symmetric Dirac-Hartree-Fock potential. We implement the DKB method using B-spline basis sets and compare its performance with the widely-employed approach of Notre Dame (ND) group [W.R. Johnson, S.A. Blundell, J. Sapirstein, Phys. Rev. A 37 (1988) 307-315]. We compare the performance of the ND and DKB methods by computing various properties of Cs atom: energies, hyperfine integrals, the parity-non-conserving amplitude of the 6s-7s transition, and the second-order many-body correction to the removal energy of the valence electrons. We find that for a comparable size of the basis set the accuracy of both methods is similar for matrix elements accumulated far from the nuclear region. However, for atomic properties determined by small distances, the DKB method outperforms the ND approach. In addition, we present a strategy for optimizing the size of the basis sets by choosing progressively smaller number of basis functions for increasingly higher partial waves. This strategy exploits suppression of contributions of high partial waves to typical many-body correlation corrections.

Quantum dynamics of the vibrations of helium bound to the nanosurface of a large planar organic molecule: phthalocyanine . He van der Waals complex.

PubMed

Gibbons, Brittney R; Xu, Minzhong; Bacić, Zlatko

2009-04-23

We report rigorous quantum three-dimensional calculations of highly excited intermolecular vibrational states of the van der Waals (vdW) complex phthalocyanine.He (Pc.He). The Pc molecule was treated as rigid and the intermolecular potential energy surface (IPES) was represented as a sum of atom-atom Lennard-Jones pair potentials. The IPES has four equivalent global minima on the diagonals of the square-shaped Pc, inside its five-membered rings, and four slightly shallower local minima between them, creating a distinctive corrugation pattern of the molecular nanosurface. The vdW vibrational states analyzed in this work extend to about two-thirds of the well depth of the IPES. For the assignment of the in-plane (xy) vdW vibrational excitations it was necessary to resort to two sets of quantum numbers, the Cartesian quantum numbers [nu(x), nu(y)] and the quantum numbers (v, l) of the 2D isotropic oscillator, depending on the nodal structure and the symmetry of the wave functions. The delocalization of the He atom parallel to the molecular surface is large already in the ground vdW state. It increases rapidly with the number of quanta in the in-plane vdW vibrations, with the maximum root-mean-square amplitudes Deltax and Deltay of about 7 au at the excitation energies around 40 cm(-1). The wave functions of the highly excited states tend to be delocalized over the entire nanosurface and often have a square shape, reflecting that of the substrate.

Heating of trapped ultracold atoms by collapse dynamics

NASA Astrophysics Data System (ADS)

Laloë, Franck; Mullin, William J.; Pearle, Philip

2014-11-01

The continuous spontaneous localization (CSL) theory alters the Schrödinger equation. It describes wave-function collapse as a dynamical process instead of an ill-defined postulate, thereby providing macroscopic uniqueness and solving the so-called measurement problem of standard quantum theory. CSL contains a parameter λ giving the collapse rate of an isolated nucleon in a superposition of two spatially separated states and, more generally, characterizing the collapse time for any physical situation. CSL is experimentally testable, since it predicts some behavior different from that predicted by standard quantum theory. One example is the narrowing of wave functions, which results in energy imparted to particles. Here we consider energy given to trapped ultracold atoms. Since these are the coldest samples under experimental investigation, it is worth inquiring how they are affected by the CSL heating mechanism. We examine the CSL heating of a Bose-Einstein condensate (BEC) in contact with its thermal cloud. Of course, other mechanisms also provide heat and also particle loss. From varied data on optically trapped cesium BECs, we present an energy audit for known heating and loss mechanisms. The result provides an upper limit on CSL heating and thereby an upper limit on the parameter λ . We obtain λ ≲1 (±1 ) ×10-7 s-1.

Behavior of the Position-Spread Tensor in Diatomic Systems.

PubMed

Brea, Oriana; El Khatib, Muammar; Angeli, Celestino; Bendazzoli, Gian Luigi; Evangelisti, Stefano; Leininger, Thierry

2013-12-10

The behavior of the Position-Spread Tensor (Λ) in a series of light diatomic molecules (either neutral or negative ions) is investigated at a Full Configuration Interaction level. This tensor, which is the second moment cumulant of the total position operator, is invariant with respect to molecular translations, while its trace is also rotationally invariant. Moreover, the tensor is additive in the case of noninteracting subsystems and can be seen as an intrinsic property of a molecule. In the present work, it is shown that the longitudinal component of the tensor, Λ∥, which is small for internuclear distances close to the equilibrium, tends to grow if the bond is stretched. A maximum is reached in the region of the bond breaking, then Λ∥ decreases and converges toward the isolated-atom value. The degenerate transversal components, Λ⊥, on the other hand, usually have a monotonic growth toward the atomic value. The Position Spread is extremely sensitive to reorganization of the molecular wave function, and it becomes larger in the case of an increase of the electron mobility, as illustrated by the neutral-ionic avoided crossing in LiF. For these reasons, the Position Spread can be an extremely useful property that characterizes the nature of the wave function in a molecular system.

Phononic crystals of spherical particles: A tight binding approach

NASA Astrophysics Data System (ADS)

Mattarelli, M.; Secchi, M.; Montagna, M.

2013-11-01

The vibrational dynamics of a fcc phononic crystal of spheres is studied and compared with that of a single free sphere, modelled either by a continuous homogeneous medium or by a finite cluster of atoms. For weak interaction among the spheres, the vibrational dynamics of the phononic crystal is described by shallow bands, with low degree of dispersion, corresponding to the acoustic spheroidal and torsional modes of the single sphere. The phonon displacements are therefore related to the vibrations of a sphere, as the electron wave functions in a crystal are related to the atomic wave functions in a tight binding model. Important dispersion is found for the two lowest phonon bands, which correspond to zero frequency free translation and rotation of a free sphere. Brillouin scattering spectra are calculated at some values of the exchanged wavevectors of the light, and compared with those of a single sphere. With weak interaction between particles, given the high acoustic impedance mismatch in dry systems, the density of phonon states consist of sharp bands separated by large gaps, which can be well accounted for by a single particle model. Based on the width of the frequency gaps, tunable with the particle size, and on the small number of dispersive acoustic phonons, such systems may provide excellent materials for application as sound or heat filters.

Plane wave density functional molecular dynamics study of exothermic reactions of Al/CuO thermites

NASA Astrophysics Data System (ADS)

Oloriegbe, Suleiman; Sewell, Thomas; Chen, Zhen; Jiang, Shan; Gan, Yong

2014-03-01

Exothermic reactions between nanosize aluminum (Al) and copper oxide (CuO) structures are of current interest because of their high reaction enthalpy and energy density which exceed those of traditional monomolecular energetic compounds such as TNT, RDX, and HMX. In this work, molecular dynamics simulations with forces obtained from plane wave density functional theory are used to investigate the atomic-scale and electronic processes that occur during the fast thermite reactions between Al and CuO nanostructures under adiabatic conditions. Aluminum surfaces in contact with O-exposed and Cu-exposed CuO surfaces are studied. Starting from initial temperature T = 800 K, we have observed: faster chemical reaction at the oxygen-rich interface during the initial 0.5 ps, linear temperature rise, and fast oxygen diffusion into the Al region with the rate 1.87 X 10-3 cm2/s. The density-derived electrostatic and chemical method is used to evaluate the net atomic charges and charge transfer during the important redox processes. High charge density around the oxygen-exposed interface may be responsible for the faster initial reactions at that interface. The overall reaction rate, determined using the time evolution of Cu-O charge orbital overlap population, is approximately first order.

Plane wave packet formulation of atom-plus-diatom quantum reactive scattering.

PubMed

Althorpe, Stuart C

2004-07-15

We recently interpreted several reactive scattering experiments using a plane wave packet (PWP) formulation of quantum scattering theory [see, e.g., S. C. Althorpe, F. Fernandez-Alonso, B. D. Bean, J. D. Ayers, A. E. Pomerantz, R. N. Zare, and E. Wrede, Nature (London) 416, 67 (2002)]. This paper presents the first derivation of this formulation for atom-plus-diatom reactive scattering, and explains its relation to conventional time-independent reactive scattering. We generalize recent results for spherical-particle scattering [S. C. Althorpe, Phys. Rev. A 69, 042702 (2004)] to atom-rigid-rotor scattering in the space-fixed frame, atom-rigid-rotor scattering in the body-fixed frame, and finally A+BC rearrangement scattering. The reactive scattering is initiated by a plane wave packet, describing the A+BC reagents in center-of-mass scattering coordinates, and is detected by projecting onto a series of AC+B (or AB+C) plane wave "probe" packets. The plane wave packets are localized at the closest distance from the scattering center at which the interaction potential can be neglected. The time evolution of the initial plane wave packet provides a clear visualization of the scattering into space of the reaction products. The projection onto the probe packets yields the time-independent, state-to-state scattering amplitude, and hence the differential cross section. We explain how best to implement the PWP approach in a numerical computation, and illustrate this with a detailed application to the H+D2 reaction. (c) 2004 American Institute of Physics

Functionalization of multi-walled carbon nanotubes with iron phthalocyanine via a liquid chemical reaction for oxygen reduction in alkaline media

NASA Astrophysics Data System (ADS)

Yan, Xiaomei; Xu, Xiao; Liu, Qin; Guo, Jia; Kang, Longtian; Yao, Jiannian

2018-06-01

Iron single-atom catalyst in form of iron-nitrogen-carbon structure possesses the excellent catalytic activity in various chemical reactions. However, exploring a sustainable and stable single-atom metal catalyst still faces a great challenge due to low yield and complicated synthesis. Here, we report a functional multi-wall carbon nanotubes modified with iron phthalocyanine molecules via a liquid chemical reaction and realize the performance of similar single-atom catalysis for oxygen reduction reaction. A serial of characterizations strongly imply the structure change of iron phthalocyanine molecule and its close recombination with multi-wall carbon nanotubes, which are in favor of ORR catalysis. Compared to commercial platinum-carbon catalyst, composites exhibit superior activity for oxygen reduction reaction with higher half-wave potential (0.86 V), lower Tafel slope (38 mV dec-1), higher limiting current density and excellent electrochemical stability. The corresponding Zinc-air battery also presents higher maximum power density and discharge stability. Therefore, these findings provide a facile route to synthesize a highly efficient non-precious metal carbon-based catalyst.

Spray formation processes of impinging jet injectors

NASA Technical Reports Server (NTRS)

Anderson, W. E.; Ryan, H. M.; Pal, S.; Santoro, R. J.

1993-01-01

A study examining impinging liquid jets has been underway to determine physical mechanisms responsible for combustion instabilities in liquid bi-propellant rocket engines. Primary atomization has been identified as an important process. Measurements of atomization length, wave structure, and drop size and velocity distribution were made under various ambient conditions. Test parameters included geometric effects and flow effects. It was observed that pre-impingement jet conditions, specifically whether they were laminar or turbulent, had the major effect on primary atomization. Comparison of the measurements with results from a two dimensional linear aerodynamic stability model of a thinning, viscous sheet were made. Measured turbulent impinging jet characteristics were contrary to model predictions; the structure of waves generated near the point of jet impingement were dependent primarily on jet diameter and independent of jet velocity. It has been postulated that these impact waves are related to pressure and momentum fluctuations near the impingement region and control the eventual disintegration of the liquid sheet into ligaments. Examination of the temporal characteristics of primary atomization (ligament shedding frequency) strongly suggests that the periodic nature of primary atomization is a key process in combustion instability.

Formation of Triplet Positron-helium Bound State by Stripping of Positronium Atoms in Collision with Ground State Helium

NASA Technical Reports Server (NTRS)

Drachman, Richard J.

2006-01-01

Formation of triplet positron-helium bound state by stripping of positronium atoms in collision with ground state helium JOSEPH DI RlENZI, College of Notre Dame of Maryland, RICHARD J. DRACHMAN, NASA/Goddard Space Flight Center - The system consisting of a positron and a helium atom in the triplet state e(+)He(S-3)(sup e) was conjectured long ago to be stable [1]. Its stability has recently been established rigorously [2], and the values of the energies of dissociation into the ground states of Ps and He(+) have also been reported [3] and [4]. We have evaluated the cross-section for this system formed by radiative attachment of a positron in triplet He state and found it to be small [5]. The mechanism of production suggested here should result in a larger cross-section (of atomic size) which we are determining using the Born approximation with simplified initial and final wave functions.

Theoretical L-shell Coster-Kronig energies 11 or equal to z or equal to 103

NASA Technical Reports Server (NTRS)

Chen, M. H.; Crasemann, B.; Huang, K. N.; Aoyagi, M.; Mark, H.

1976-01-01

Relativistic relaxed-orbital calculations of L-shell Coster-Kronig transition energies have been performed for all possible transitions in atoms with atomic numbers. Hartree-Fock-Slater wave functions served as zeroth-order eigenfunctions to compute the expectation of the total Hamiltonian. A first-order approximation to the local approximation was thus included. Quantum-electrodynamic corrections were made. Each transition energy was computed as the difference between results of separate self-consistent-field calculations for the initial, singly ionized state and the final two-hole state. The following quantities are listed: total transition energy, 'electric' (Dirac-Hartree-Fock-Slater) contribution, magnetic and retardation contributions, and contributions due to vacuum polarization and self energy.

Validity of virial theorem in all-electron mixed basis density functional, Hartree–Fock, and GW calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuwahara, Riichi; Accelrys K. K., Kasumigaseki Tokyu Building 17F, 3-7-1 Kasumigaseki, Chiyoda-ku, Tokyo 100-0013; Tadokoro, Yoichi

In this paper, we calculate kinetic and potential energy contributions to the electronic ground-state total energy of several isolated atoms (He, Be, Ne, Mg, Ar, and Ca) by using the local density approximation (LDA) in density functional theory, the Hartree–Fock approximation (HFA), and the self-consistent GW approximation (GWA). To this end, we have implemented self-consistent HFA and GWA routines in our all-electron mixed basis code, TOMBO. We confirm that virial theorem is fairly well satisfied in all of these approximations, although the resulting eigenvalue of the highest occupied molecular orbital level, i.e., the negative of the ionization potential, is inmore » excellent agreement only in the case of the GWA. We find that the wave function of the lowest unoccupied molecular orbital level of noble gas atoms is a resonating virtual bound state, and that of the GWA spreads wider than that of the LDA and thinner than that of the HFA.« less

Trial wave functions for ring-trapped ions and neutral atoms: Microscopic description of the quantum space-time crystal

NASA Astrophysics Data System (ADS)

Yannouleas, Constantine; Landman, Uzi

2017-10-01

A constructive theoretical platform for the description of quantum space-time crystals uncovers for N interacting and ring-confined rotating particles the existence of low-lying states with proper space-time crystal behavior. The construction of the corresponding many-body trial wave functions proceeds first via symmetry breaking at the mean-field level followed by symmetry restoration using projection techniques. The ensuing correlated many-body wave functions are stationary states and preserve the rotational symmetries, and at the same time they reflect the point-group symmetries of the mean-field crystals. This behavior results in the emergence of sequences of select magic angular momenta Lm. For angular-momenta away from the magic values, the trial functions vanish. Symmetry breaking beyond the mean-field level can be induced by superpositions of such good-Lm many-body stationary states. We show that superposing a pair of adjacent magic angular momenta states leads to formation of special broken-symmetry states exhibiting quantum space-time-crystal behavior. In particular, the corresponding particle densities rotate around the ring, showing undamped and nondispersed periodic crystalline evolution in both space and time. The experimental synthesis of such quantum space-time-crystal wave packets is predicted to be favored in the vicinity of ground-state energy crossings of the Aharonov-Bohm-type spectra accessed via an externally applied, natural or synthetic, magnetic field. These results are illustrated here for Coulomb-repelling fermionic ions and for a lump of contact-interaction attracting bosons.

The giant acoustic atom - a single quantum system with a deterministic time delay

NASA Astrophysics Data System (ADS)

Guo, Lingzhen; Grimsmo, Arne; Frisk Kockum, Anton; Pletyukhov, Mikhail; Johansson, Göran

2017-04-01

We investigate the quantum dynamics of a single transmon qubit coupled to surface acoustic waves (SAWs) via two distant connection points. Since the acoustic speed is five orders of magnitude slower than the speed of light, the travelling time between the two connection points needs to be taken into account. Therefore, we treat the transmon qubit as a giant atom with a deterministic time delay. We find that the spontaneous emission of the system, formed by the giant atom and the SAWs between its connection points, initially follows a polynomial decay law instead of an exponential one, as would be the case for a small atom. We obtain exact analytical results for the scattering properties of the giant atom up to two-phonon processes by using a diagrammatic approach. The time delay gives rise to novel features in the reflection, transmission, power spectra, and second-order correlation functions of the system. Furthermore, we find the short-time dynamics of the giant atom for arbitrary drive strength by a numerically exact method for open quantum systems with a finite-time-delay feedback loop. L. G. acknowledges financial support from Carl-Zeiss Stiftung (0563-2.8/508/2).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matanovic, Ivana; Atanassov, Plamen; Kiefer, Boris

The structural equilibrium parameters, the adsorption energies, and the vibrational frequencies of the nitrogen molecule and the hydrogen atom adsorbed on the (111) surface of rhodium have been investigated using different generalized-gradient approximation (GGA), nonlocal correlation, meta-GGA, and hybrid functionals, namely, Perdew, Burke, and Ernzerhof (PBE), Revised-RPBE, vdW-DF, Tao, Perdew, Staroverov, and Scuseria functional (TPSS), and Heyd, Scuseria, and Ernzerhof (HSE06) functional in the plane wave formalism. Among the five tested functionals, nonlocal vdW-DF and meta-GGA TPSS functionals are most successful in describing energetics of dinitrogen physisorption to the Rh(111) surface, while the PBE functional provides the correct chemisorption energymore » for the hydrogen atom. It was also found that TPSS functional produces the best vibrational spectra of the nitrogen molecule and the hydrogen atom on rhodium within the harmonic formalism with the error of 22.62 and 21.1% for the NAN stretching and RhAH stretching frequency. Thus, TPSS functional was proposed as a method of choice for obtaining vibrational spectra of low weight adsorbates on metallic surfaces within the harmonic approximation. At the anharmonic level, by decoupling the RhAH and NAN stretching modes from the bulk phonons and by solving one- and two-dimensional Schr€odinger equation associated with the RhAH, RhAN, and NAN potential energy we calculated the anharmonic correction for NAN and RhAH stretching modes as 231 cm21 and 277 cm21 at PBE level. Anharmonic vibrational frequencies calculated with the use of the hybrid HSE06 function are in best agreement with available experiments.« less

Evanescent Wave Atomic Mirror

NASA Astrophysics Data System (ADS)

Ghezali, S.; Taleb, A.

2008-09-01

A research project at the "Laboratoire d'électronique quantique" consists in a theoretical study of the reflection and diffraction phenomena via an atomic mirror. This poster presents the principle of an atomic mirror. Many groups in the world have constructed this type of atom optics experiments such as in Paris-Orsay-Villetaneuse (France), Stanford-Gaithersburg (USA), Munich-Heidelberg (Germany), etc. A laser beam goes into a prism with an incidence bigger than the critical incidence. It undergoes a total reflection on the plane face of the prism and then exits. The transmitted resulting wave out of the prism is evanescent and repulsive as the frequency detuning of the laser beam compared to the atomic transition δ = ωL-ω0 is positive. The cold atomic sample interacts with this evanescent wave and undergoes one or more elastic bounces by passing into backward points in its trajectory because the atoms' kinetic energy (of the order of the μeV) is less than the maximum of the dipolar potential barrier ℏΩ2/Δ where Ω is the Rabi frequency [1]. In fact, the atoms are cooled and captured in a magneto-optical trap placed at a distance of the order of the cm above the prism surface. The dipolar potential with which interact the slow atoms is obtained for a two level atom in a case of a dipolar electric transition (D2 Rubidium transition at a wavelength of 780nm delivered by a Titane-Saphir laser between a fundamental state Jf = l/2 and an excited state Je = 3/2). This potential is corrected by an attractive Van der Waals term which varies as 1/z3 in the Lennard-Jones approximation (typical atomic distance of the order of λ0/2π where λ0 is the laser wavelength) and in 1/z4 if the distance between the atom and its image in the dielectric is big in front of λ0/2π. This last case is obtained in a quantum electrodynamic calculation by taking into account an orthornormal base [2]. We'll examine the role of spontaneous emission for which the rate is inversely proportional to the detuning δ and is responsible of the non specular aspect of the atomic reflection (atomic diffusion). In the contrary, we note that the specularity of the reflection preserve the coherence of the atomic wave packet. The atoms will constitute a probe of the rugosity of the prism surface which can be imperfect or super-polished.

Dipole-dipole interaction in cavity QED: The weak-coupling, nondegenerate regime

NASA Astrophysics Data System (ADS)

Donaire, M.; Muñoz-Castañeda, J. M.; Nieto, L. M.

2017-10-01

We compute the energies of the interaction between two atoms placed in the middle of a perfectly reflecting planar cavity, in the weak-coupling nondegenerate regime. Both inhibition and enhancement of the interactions can be obtained by varying the size of the cavity. We derive exact expressions for the dyadic Green's function of the cavity field which mediates the interactions and apply time-dependent quantum perturbation theory in the adiabatic approximation. We provide explicit expressions for the van der Waals potentials of two polarizable atomic dipoles and the electrostatic potential of two induced dipoles. We compute the van der Waals potentials in three different scenarios: two atoms in their ground states, two atoms excited, and two dissimilar atoms with one of them excited. In addition, we calculate the phase-shift rate of the two-atom wave function in each case. The effect of the two-dimensional confinement of the electromagnetic field on the dipole-dipole interactions is analyzed. This effect depends on the atomic polarization. For dipole moments oriented parallel to the cavity plates, both the electrostatic and the van der Waals interactions are exponentially suppressed for values of the cavity width much less than the interatomic distance, whereas for values of the width close to the interatomic distance, the strength of both interactions is higher than their values in the absence of cavity. For dipole moments perpendicular to the plates, the strength of the van der Waals interaction decreases for values of the cavity width close to the interatomic distance, while it increases for values of the width much less than the interatomic distance with respect to its strength in the absence of cavity. We illustrate these effects by computing the dipole-dipole interactions between two alkali atoms in circular Rydberg states.

Continuous Wave Ring-Down Spectroscopy Diagnostic for Measuring Argon Ion and Neutral Velocity Distribution Functions in a Helicon Plasma

NASA Astrophysics Data System (ADS)

McCarren, Dustin; Vandervort, Robert; Soderholm, Mark; Carr, Jerry, Jr.; Galante, Matthew; Magee, Richard; Scime, Earl

2013-10-01

Cavity Ring-Down Spectroscopy CRDS is a proven, ultra-sensitive, cavity enhanced absorption spectroscopy technique. When combined with a continuous wavelength (CW) diode laser that has a sufficiently narrow line width, the Doppler broadened absorption line, i.e., the velocity distribution functions (IVDFs), can be measured. Measurements of IVDFS can be made using established techniques, such as laser induced fluorescence (LIF). However, LIF suffers from the requirement that the initial state of the LIF sequence have a substantial density. This usually limits LIF to ions and atoms with large metastable state densities for the given plasma conditions. CW-CRDS is considerably more sensitive than LIF and can potentially be applied to much lower density populations of ion and atom states. In this work we present ongoing measurements of the CW-CRDS diagnostic and discuss the technical challenges of using CW-CRDS to make measurements in a helicon plasma.

Comparison of Atom Interferometers and Light Interferometers as Space-Based Gravitational Wave Detectors

NASA Technical Reports Server (NTRS)

Baker, John G.

2012-01-01

We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe.

Comparison of atom interferometers and light interferometers as space-based gravitational wave detectors.

PubMed

Baker, John G; Thorpe, J I

2012-05-25

We consider a class of proposed gravitational-wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, noninertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g., multiple-arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and, in principle, favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe.

Virtual detector theory for strong-field atomic ionization

NASA Astrophysics Data System (ADS)

Wang, Xu; Tian, Justin; Eberly, J. H.

2018-04-01

A virtual detector (VD) is an imaginary device located at a fixed position in space that extracts information from the wave packet passing through it. By recording the particle momentum and the corresponding probability current at each time, the VDs can accumulate and build the differential momentum distribution of the particle, in a way that resembles real experiments. A mathematical proof is given for the equivalence of the differential momentum distribution obtained by the VD method and by Fourier transforming the wave function. In addition to being a tool for reducing the computational load, VDs have also been found useful in interpreting the ultrafast strong-field ionization process, especially the controversial quantum tunneling process.

Biphoton Generation Driven by Spatial Light Modulation: Parallel-to-Series Conversion

NASA Astrophysics Data System (ADS)

Zhao, Luwei; Guo, Xianxin; Sun, Yuan; Su, Yumian; Loy, M. M. T.; Du, Shengwang

2016-05-01

We demonstrate the generation of narrowband biphotons with controllable temporal waveform by spontaneous four-wave mixing in cold atoms. In the group-delay regime, we study the dependence of the biphoton temporal waveform on the spatial profile of the pump laser beam. By using a spatial light modulator, we manipulate the spatial profile of the pump laser and map it onto the two-photon entangled temporal wave function. This parallel-to-series conversion (or spatial-to-temporal mapping) enables coding the parallel classical information of the pump spatial profile to the sequential temporal waveform of the biphoton quantum state. The work was supported by the Hong Kong RGC (Project No. 601113).

Atomic data and line intensities for the S V ion

NASA Astrophysics Data System (ADS)

Iorga, C.; Stancalie, V.

2017-05-01

The energy levels, oscillator strengths, spontaneous radiative decay rates, lifetimes and electron impact collision strengths have been obtained for the [ Ne ] 3s nl, [ Ne ] 3p nl, [ Ne ] 3d nl configurations belonging to S V ion, with n ≤ 7 and l ≤ 4, resulting in 567 fine-structure levels. The calculations have been performed within the fully relativistic Flexible Atomic Code (FAC, Gu, 2008) framework and the distorted wave approximation. To attain the desired accuracy for the levels energy, the valence-valence and valence-core correlations have been taken care of by including 96 configuration state functions (CSFs) in the model, reaching a total of 3147 fine-structure levels. Two separate calculations have been performed with the local central potential computed for two different average configurations. A third calculation is also performed without the addition of the core-excited states in the atomic model for completeness. The effects of slightly different mean configurations and valence-core correlations on the energy levels and decay rates are investigated. The collision data have been computed employing the relativistic distorted-wave method along with the atomic model containing the 96 CSFs and corresponding to the ground state mean configuration. The collision strengths corresponding to excitation from the first four fine-structure levels are given for five energy values of the scattered electron 2.65, 6.18, 11.02, 17.36, 25.43 Rydberg, plus an additional variable small energy value near the threshold. A collisional-radiative model has been employed to solve the rate equations for the populations of the 567 fine-structure levels, for a temperature of LogTE(K) = 5.2 corresponding to the maximum abundance of S V, and at densities 106-1016cm-3, assuming a Maxwellian electron energy distribution function and black body radiation of temperature 6000 K and dilution factor 0.35 for the photon distribution function. The main processes responsible for the level population variations are the electron-impact collisional excitation and the radiative decay along with their inverse processes. As a result, the level populations along with the spectral high-line intensity ratios are provided.

Whispering gallery states of neutrons and anti-hydrogen atoms and their applications to fundamental and surface physics

NASA Astrophysics Data System (ADS)

Nesvizhevsky, Valery

2013-03-01

The `whispering gallery' effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It is intensively used and explored due to its numerous crucial applications. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for neutrons and (anti)atoms. For (anti)matter waves, it includes a new feature: a massive particle is settled in quantum states, with parameters depending on its mass. In this talk, we present the first observation of the quantum whispering-gallery effect for matter particles (cold neutrons) 1-2. This phenomenon provides an example of an exactly solvable problem analogous to the `quantum bouncer'; it is complementary to recently discovered gravitational quantum states of neutrons3. These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a quantum state. Deeply bound long-living states are weakly sensitive to surface potential; highly excited short-living states are very sensitive to the wall nuclear potential shape. Therefore, they are a promising tool for studying fundamental neutron-matter interactions, quantum neutron optics and surface physics effects. Analogous phenomena could be measured with atoms and anti-atoms 4-5.

Kinetics of oxygen atom formation during the oxidation of methane behind shock waves

NASA Technical Reports Server (NTRS)

Jachimowski, C. J.

1974-01-01

An experimental and analytical study of the formation of oxygen atoms during the oxidation of methane and methane-hydrogen mixtures behind incident shock waves was carried out over the temperature range 1790-2584 K at reaction pressures between 1.2 and 1.7 atm. Oxygen atom levels were determined indirectly by measurement of emission from reaction of O with CO. On the basis of these data and ignition-delay data reported in the literature, a kinetic scheme for methane oxidation was assembled. The proposed kinetic mechanism, in general, predicts higher peak oxygen atom levels than the current oxidation mechanisms proposed by Bowman and Seery and by Skinner and his co-workers.

Comparative Sensitivities of Gravitational Wave Detectors Based on Atom Interferometers and Light Interferometers

NASA Technical Reports Server (NTRS)

Baker, John G.; Thorpe, J. I.

2012-01-01

We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe. Whether this potential advantage outweighs the additional complexity associated with including atom interferometers will require further study.

On ionizing shock waves

NASA Astrophysics Data System (ADS)

Kaniel, A.; Igra, O.; Ben-Dor, G.; Mond, M.

The flow field in the ionizing relaxation zone developed behind a normal shock wave in an electrically neutral, homogeneous, two temperature mixture of thermally ideal gases (molecules, atoms, ions, electrons) was numerically solved. The heat transfer between the electron gas and the other components was taken into account while all the other transport phenomena (molecular, turbulent and radiative) were neglected in the relaxation zone, since it is dominated by inelastic collisions. The threshold cross sections measured by Specht (1981), for excitation of argon by electron collisions, were used. The calculated results show good agreement with the results of the shock tube experiments presented by Glass and Liu (1978), especially in the electron avalanche region. A critical examination was made of the common assumptions regarding the average energy with which electrons are produced by atom-atom collisions and the relative effectiveness of atom-atom collisions (versus electron-atom collisions) in ionizing excited argon.

Controllable vacuum-induced diffraction of matter-wave superradiance using an all-optical dispersive cavity

NASA Astrophysics Data System (ADS)

Su, Shih-Wei; Lu, Zhen-Kai; Gou, Shih-Chuan; Liao, Wen-Te

2016-10-01

Cavity quantum electrodynamics (CQED) has played a central role in demonstrating the fundamental principles of the quantum world, and in particular those of atom-light interactions. Developing fast, dynamical and non-mechanical control over a CQED system is particularly desirable for controlling atomic dynamics and building future quantum networks at high speed. However conventional mirrors do not allow for such flexible and fast controls over their coupling to intracavity atoms mediated by photons. Here we theoretically investigate a novel all-optical CQED system composed of a binary Bose-Einstein condensate (BEC) sandwiched by two atomic ensembles. The highly tunable atomic dispersion of the CQED system enables the medium to act as a versatile, all-optically controlled atomic mirror that can be employed to manipulate the vacuum-induced diffraction of matter-wave superradiance. Our study illustrates a innovative all-optical element of atomtroics and sheds new light on controlling light-matter interactions.

Measuring Gravitation Using Polarization Spectroscopy

NASA Technical Reports Server (NTRS)

Matsko, Andrey; Yu, Nan; Maleki, Lute

2004-01-01

A proposed method of measuring gravitational acceleration would involve the application of polarization spectroscopy to an ultracold, vertically moving cloud of atoms (an atomic fountain). A related proposed method involving measurements of absorption of light pulses like those used in conventional atomic interferometry would yield an estimate of the number of atoms participating in the interferometric interaction. The basis of the first-mentioned proposed method is that the rotation of polarization of light is affected by the acceleration of atoms along the path of propagation of the light. The rotation of polarization is associated with a phase shift: When an atom moving in a laboratory reference interacts with an electromagnetic wave, the energy levels of the atom are Doppler-shifted, relative to where they would be if the atom were stationary. The Doppler shift gives rise to changes in the detuning of the light from the corresponding atomic transitions. This detuning, in turn, causes the electromagnetic wave to undergo a phase shift that can be measured by conventional means. One would infer the gravitational acceleration and/or the gradient of the gravitational acceleration from the phase measurements.

Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy

NASA Technical Reports Server (NTRS)

Cantrell, John H.; Cantrell, Sean A.

2010-01-01

The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.

Transverse effects in nonlinear optics: Toward the photon superfluid

NASA Astrophysics Data System (ADS)

McCormick, Colin Fraser

Nonlinear optics displays a wealth of transverse effects. These effects are particularly rich in the presence of an optical cavity. Many considerations suggest that in a Kerr nonlinear cavity a new state of light known as a "photon superfluid" can form, with strong analogies to atomic superfluids. The conditions for the formation of the photon superfluid include requirements on the cavity, input light fields and the nonlinear medium as well as various timescales. The most favorable candidate nonlinear medium for observing the photon super-fluid is an atomic vapor. With a strong and fast Kerr effect, atomic vapors also have the advantage of a Kerr coefficient that is tunable in both magnitude and sign. A series of z-scan experiments in far-detuned atomic rubidium vapor is reported, measuring the Kerr coefficient and determining its functional dependence on detuning to be that of a Doppler-broadened two-level model with adiabatic following of the electric field by the atom pseudomoment. Saturation effects are found to be important. Z-scan measurements for detunings within the Doppler profile are shown to agree well with numerical simulations based on the Doppler-broadened model. Agreement between absorptive and refractive non-linear coefficients is evidence of the Kramers-Kronig relations at work, even in this nonlinear system. The formation of the photon superfluid is discussed and the calculation of a new process, nearly collinear four-wave mixing, is presented. This process is essentially an inverse beam filamentation that is likely to be the underlying physical mechanism for transverse cooling and condensation of photons in a nonlinear optical cavity. Nearly collinear four-wave mixing may also be related to phenomena in general nonlinear physics, including modulation instability and Fermi-Pasta-Ulam recurrence.

Implementation of highly parallel and large scale GW calculations within the OpenAtom software

NASA Astrophysics Data System (ADS)

Ismail-Beigi, Sohrab

The need to describe electronic excitations with better accuracy than provided by band structures produced by Density Functional Theory (DFT) has been a long-term enterprise for the computational condensed matter and materials theory communities. In some cases, appropriate theoretical frameworks have existed for some time but have been difficult to apply widely due to computational cost. For example, the GW approximation incorporates a great deal of important non-local and dynamical electronic interaction effects but has been too computationally expensive for routine use in large materials simulations. OpenAtom is an open source massively parallel ab initiodensity functional software package based on plane waves and pseudopotentials (http://charm.cs.uiuc.edu/OpenAtom/) that takes advantage of the Charm + + parallel framework. At present, it is developed via a three-way collaboration, funded by an NSF SI2-SSI grant (ACI-1339804), between Yale (Ismail-Beigi), IBM T. J. Watson (Glenn Martyna) and the University of Illinois at Urbana Champaign (Laxmikant Kale). We will describe the project and our current approach towards implementing large scale GW calculations with OpenAtom. Potential applications of large scale parallel GW software for problems involving electronic excitations in semiconductor and/or metal oxide systems will be also be pointed out.

Geminal embedding scheme for optimal atomic basis set construction in correlated calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sorella, S., E-mail: sorella@sissa.it; Devaux, N.; Dagrada, M., E-mail: mario.dagrada@impmc.upmc.fr

2015-12-28

We introduce an efficient method to construct optimal and system adaptive basis sets for use in electronic structure and quantum Monte Carlo calculations. The method is based on an embedding scheme in which a reference atom is singled out from its environment, while the entire system (atom and environment) is described by a Slater determinant or its antisymmetrized geminal power (AGP) extension. The embedding procedure described here allows for the systematic and consistent contraction of the primitive basis set into geminal embedded orbitals (GEOs), with a dramatic reduction of the number of variational parameters necessary to represent the many-body wavemore » function, for a chosen target accuracy. Within the variational Monte Carlo method, the Slater or AGP part is determined by a variational minimization of the energy of the whole system in presence of a flexible and accurate Jastrow factor, representing most of the dynamical electronic correlation. The resulting GEO basis set opens the way for a fully controlled optimization of many-body wave functions in electronic structure calculation of bulk materials, namely, containing a large number of electrons and atoms. We present applications on the water molecule, the volume collapse transition in cerium, and the high-pressure liquid hydrogen.« less

Lasers, Understanding the Atom Series.

ERIC Educational Resources Information Center

Hellman, Hal

This booklet is one of the booklets in the "Understanding the Atom Series" published by the U. S. Atomic Energy Commission for high school science teachers and their students. Basic information for understanding the laser is provided including discussion of the electromagnetic spectrum, radio waves, light and the atom, coherent light, controlled…

Investigating tunneling process of atom exposed in circularly polarized strong-laser field

NASA Astrophysics Data System (ADS)

Yuan, MingHu; Xin, PeiPei; Chu, TianShu; Liu, HongPing

2017-03-01

We propose a method for studying the tunneling process by analyzing the instantaneous ionization rate of a circularly polarized laser. A numerical calculation shows that, for an atom exposed to a long laser pulse, if its initial electronic state wave function is non-spherical symmetric, the delayed phase shift of the ionization rate vs the laser cycle period in real time in the region close to the peak intensity of the laser pulse can be used to probe the tunneling time. In this region, an obvious time delay phase shift of more than 190 attoseconds is observed. Further study shows that the atom has a longer tunneling time in the ionization under a shorter wavelength laser pulse. In our method, a Wigner rotation technique is employed to numerically solve the time-dependent Schrödinger equation of a single-active electron in a three-dimensional spherical coordinate system.

Shannon entropies and Fisher information of K-shell electrons of neutral atoms

NASA Astrophysics Data System (ADS)

Sekh, Golam Ali; Saha, Aparna; Talukdar, Benoy

2018-02-01

We represent the two K-shell electrons of neutral atoms by Hylleraas-type wave function which fulfils the exact behavior at the electron-electron and electron-nucleus coalescence points and, derive a simple method to construct expressions for single-particle position- and momentum-space charge densities, ρ (r) and γ (p) respectively. We make use of the results for ρ (r) and γ (p) to critically examine the effect of correlation on bare (uncorrelated) values of Shannon information entropies (S) and of Fisher information (F) for the K-shell electrons of atoms from helium to neon. Due to inter-electronic repulsion the values of the uncorrelated Shannon position-space entropies are augmented while those of the momentum-space entropies are reduced. The corresponding Fisher information are found to exhibit opposite behavior in respect of this. Attempts are made to provide some plausible explanation for the observed response of S and F to electronic correlation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, S.; Saha, J. K.; Chandra, R.

The Rayleigh-Ritz variational technique with a Hylleraas basis set is being tested for the first time to estimate the structural modifications of a lithium atom embedded in a weakly coupled plasma environment. The Debye-Huckel potential is used to mimic the weakly coupled plasma environment. The wave functions for both the helium-like lithium ion and the lithium atom are expanded in the explicitly correlated Hylleraas type basis set which fully takes care of the electron-electron correlation effect. Due to the continuum lowering under plasma environment, the ionization potential of the system gradually decreases leading to the destabilization of the atom. Themore » excited states destabilize at a lower value of the plasma density. The estimated ionization potential agrees fairly well with the few available theoretical estimates. The variation of one and two particle moments, dielectric susceptibility and magnetic shielding constant, with respect to plasma density is also been discussed in detail.« less

Laser Assisted Free-Free Transition in Electron - Atom Collision

NASA Technical Reports Server (NTRS)

Sinha, C.; Bhatia, A. K.

2011-01-01

Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

Electron- and positron-impact atomic scattering calculations using propagating exterior complex scaling

NASA Astrophysics Data System (ADS)

Bartlett, P. L.; Stelbovics, A. T.; Rescigno, T. N.; McCurdy, C. W.

2007-11-01

Calculations are reported for four-body electron-helium collisions and positron-hydrogen collisions, in the S-wave model, using the time-independent propagating exterior complex scaling (PECS) method. The PECS S-wave calculations for three-body processes in electron-helium collisions compare favourably with previous convergent close-coupling (CCC) and time-dependent exterior complex scaling (ECS) calculations, and exhibit smooth cross section profiles. The PECS four-body double-excitation cross sections are significantly different from CCC calculations and highlight the need for an accurate representation of the resonant helium final-state wave functions when undertaking these calculations. Results are also presented for positron-hydrogen collisions in an S-wave model using an electron-positron potential of V12 = - (8 + (r1 - r2)2)-1/2. This model is representative of the full problem, and the results demonstrate that ECS-based methods can accurately calculate scattering, ionization and positronium formation cross sections in this three-body rearrangement collision.

Magneto-optical spectra and electron structure of Nd0.5Gd0.5Fe3(BO3)4 single crystal

NASA Astrophysics Data System (ADS)

Malakhovskii, A. V.; Gnatchenko, S. L.; Kachur, I. S.; Piryatinskaya, V. G.; Sukhachev, A. L.; Temerov, V. L.

2016-03-01

Polarized absorption spectra and magnetic circular dichroism (MCD) spectra of Nd0.5Gd0.5Fe3(BO3)4 single crystal were measured in the range of 10000-21000 cm-1 and at temperatures 2-300 K. On the basis of these data, in the paramagnetic state of the crystal, the 4f states of the Nd3+ ion were identified in terms of the irreducible representations and in terms of | J , ±MJ 〉 wave functions of the free atom. The changes of the Landé factor during f-f transitions were found theoretically in the | J , ±MJ 〉 wave functions approximation and were determined experimentally with the help of the measured MCD spectra. In the majority of cases the experimentally found values are close to the theoretically predicted ones.

Analytical Wave Functions for Ultracold Collisions.

NASA Astrophysics Data System (ADS)

Cavagnero, M. J.

1998-05-01

Secular perturbation theory of long-range interactions(M. J. Cavagnero, PRA 50) 2841, (1994). has been generalized to yield accurate wave functions for near threshold processes, including low-energy scattering processes of interest at ultracold temperatures. In particular, solutions of Schrödinger's equation have been obtained for motion in the combined r-6, r-8, and r-10 potentials appropriate for describing an utlracold collision of two neutral ground state atoms. Scattering lengths and effective ranges appropriate to such potentials are readily calculated at distances comparable to the LeRoy radius, where exchange forces can be neglected, thereby eliminating the need to integrate Schrödinger's equation to large internuclear distances. Our method yields accurate base pair solutions well beyond the energy range of effective range theories, making possible the application of multichannel quantum defect theory [MQDT] and R-matrix methods to the study of ultracold collisions.

Wave function delocalization and large-amplitude vibrations of helium on corrugated aromatic microsurfaces: tetracene.He and pentacene.He van der Waals complexes.

PubMed

Xu, Minzhong; Bacić, Zlatko

2007-08-09

We report accurate quantum three-dimensional calculations of highly excited intermolecular vibrational states of the van der Waals (vdW) complexes tetracene.He and pentacene.He in the S1 excited electronic state. The aromatic molecules were taken to be rigid and the intermolecular potential energy surfaces (IPESs) were modeled as a sum of atom-atom Lennard-Jones pair potentials. The IPESs are corrugated in the direction of the long (x) axis of the aromatic molecules, due to the presence of the symmetrically equivalent global double minimum for tetracene.He, and a triple minimum (central global minimum and two equivalent local minima) for pentacene.He, on each side of the aromatic plane. Both IPESs have two additional minor equivalent local minima further away from the center of the molecule. The vdW vibrational states analyzed in this work cover about 80% of the well depths of the IPESs. The mode coupling is generally weak for those states whose out-of-plane (z) mode is unexcited. However, the z-mode fundamental is strongly coupled to the short-axis (y) in-plane mode, so that the pure z-mode excitation could not be identified. The He atom exhibits large in-plane spatial delocalizaton already in the ground vdW vibrational state, which increases rapidly upon the excitation of the in-plane x and y modes, with little hindrance by the corrugation of the aromatic microsurfaces. For the vdW vibrational energies considered, the He atom spatial delocalization reaches Deltax and Deltay values of approximately 5 and 4 A, respectively, and is limited only by the finite size of the aromatic substrates. Side-crossing delocalization of the wave functions on both sides of the molecular plane is found at excitation energies >30 cm(-1), giving rise to the energy splittings of the pairs of states symmetric/antisymmetric with respect to the aromatic plane; the splittings show strong vdW vibrational mode specificity.

Transfer of a wave packet in double-well potential

NASA Astrophysics Data System (ADS)

Yang, Hai-Feng; Hu, Yao-Hua; Tan, Yong-Gang

2018-04-01

Energy potentials with double-well structures are typical in atoms and molecules systems. A manipulation scheme using Half Cycles Pulses (HCPs) is proposed to transfer a Gaussian wave packet between the two wells. On the basis of quantum mechanical simulations, the time evolution and the energy distribution of the wave packet are evaluated. The effect of time parameters, amplitude, and number of HCPs on spatial and energy distribution of the final state and transfer efficiency are investigated. After a carefully tailored HCPs sequence is applied to the initial wave packet localized in one well, the final state is a wave packet localized in the other well and populated at the lower energy levels with narrower distribution. The present scheme could be used to control molecular reactions and to prepare atoms with large dipole moments.

Supermode-density-wave-polariton condensation with a Bose–Einstein condensate in a multimode cavity

PubMed Central

Kollár, Alicia J.; Papageorge, Alexander T.; Vaidya, Varun D.; Guo, Yudan; Keeling, Jonathan; Lev, Benjamin L.

2017-01-01

Phase transitions, where observable properties of a many-body system change discontinuously, can occur in both open and closed systems. By placing cold atoms in optical cavities and inducing strong coupling between light and excitations of the atoms, one can experimentally study phase transitions of open quantum systems. Here we observe and study a non-equilibrium phase transition, the condensation of supermode-density-wave polaritons. These polaritons are formed from a superposition of cavity photon eigenmodes (a supermode), coupled to atomic density waves of a quantum gas. As the cavity supports multiple photon spatial modes and because the light–matter coupling can be comparable to the energy splitting of these modes, the composition of the supermode polariton is changed by the light–matter coupling on condensation. By demonstrating the ability to observe and understand density-wave-polariton condensation in the few-mode-degenerate cavity regime, our results show the potential to study similar questions in fully multimode cavities. PMID:28211455

Cold Rydberg molecules

NASA Astrophysics Data System (ADS)

Raithel, Georg; Zhao, Jianming

2017-04-01

Cold atomic systems have opened new frontiers at the interface of atomic and molecular physics. These include research on novel types of Rydberg molecules. Three types of molecules will be reviewed. Long-range, homonuclear Rydberg molecules, first predicted in [1] and observed in [2], are formed via low-energy electron scattering of the Rydberg electron from a ground-state atom within the Rydberg atom's volume. The binding mostly arises from S- and P-wave triplet scattering. We use a Fermi model that includes S-wave and P-wave singlet and triplet scattering, the fine structure coupling of the Rydberg atom and the hyperfine structure coupling of the 5S1/2 atom (in rubidium [3]). The hyperfine structure gives rise to mixed singlet-triplet potentials for both low-L and high-L Rydberg molecules [3]. A classification into Hund's cases [3, 4, 5] will be discussed. The talk further includes results on adiabatic potentials and adiabatic states of Rydberg-Rydberg molecules in Rb and Cs. These molecules, which have even larger bonding length than Rydberg-ground molecules, are formed via electrostatic multipole interactions. The leading interaction term of neutral Rydberg-Rydberg molecules is between two dipoles, while for ionic Rydberg molecules it is between a dipole and a monopole. NSF (PHY-1506093), NNSF of China (61475123).

GW/Bethe-Salpeter calculations for charged and model systems from real-space DFT

NASA Astrophysics Data System (ADS)

Strubbe, David A.

GW and Bethe-Salpeter (GW/BSE) calculations use mean-field input from density-functional theory (DFT) calculations to compute excited states of a condensed-matter system. Many parts of a GW/BSE calculation are efficiently performed in a plane-wave basis, and extensive effort has gone into optimizing and parallelizing plane-wave GW/BSE codes for large-scale computations. Most straightforwardly, plane-wave DFT can be used as a starting point, but real-space DFT is also an attractive starting point: it is systematically convergeable like plane waves, can take advantage of efficient domain parallelization for large systems, and is well suited physically for finite and especially charged systems. The flexibility of a real-space grid also allows convenient calculations on non-atomic model systems. I will discuss the interfacing of a real-space (TD)DFT code (Octopus, www.tddft.org/programs/octopus) with a plane-wave GW/BSE code (BerkeleyGW, www.berkeleygw.org), consider performance issues and accuracy, and present some applications to simple and paradigmatic systems that illuminate fundamental properties of these approximations in many-body perturbation theory.

Last results of DIRAC experiment on study hadronic hydrogen-like atoms at PS CERN

NASA Astrophysics Data System (ADS)

Afanasyev, Leonid

2016-04-01

Results on study the hydrogen-like atoms consisting of charged pions and Kaons are presented. The first measurement of K+ π and Kπ+ atoms lifetime was fulfilled basing on identification of 178 ± 49 Kπ pairs from the atom breakup. The measured lifetime is τ = (2.5-1.8+3.0) fs. This value is dictated by properties of the strong πK-interaction at low energy, namely S-wave πK scattering length. The first experimental value of the isospin-odd combination of S-wave πK scattering length was obtained | a0- | =1/3 |a/2 -a3/2 | = (0.11-0.04+0.09) Mπ-1 (ai for isospin I). A dedicated experiment with π+ π atoms allows further study of these already observed atoms. The preliminary results on observation of the long-lived (metastable) states of π+ π atoms are presented. The observation of long-lived states opens the possibility to measure the energy difference between ns and np states - the Lamb shift.

Laser-assisted coplanar symmetric (e, 2e) triple differential cross sections

NASA Astrophysics Data System (ADS)

Khalil, D.; Tlidi, M.; Makhoute, A.; Ajana, I.

2017-04-01

The modification due to an external linearly polarized monochromatic laser field on the dynamics of the ionization process of an atomic hydrogen by electron-impact is studied theoretically for a coplanar symmetric geometry. The interaction of the laser field with the unbound electrons is treated in a non-perturbative way. The wave functions of the ingoing and outgoing electrons in the laser field are treated as non-relativistic Volkov waves, while the interaction of the bound electron with the laser field is treated by using first-order perturbation theory, assuming that the electric field strength associated with the external laser field is much less than the atomic unit e/{a}2=5× {10}9 {{V}} {{{cm}}}-1. The influence of the laser parameters on the angular distribution is analyzed and several illustrative examples are discussed. Significant changes are noted both in the shape and magnitude of the triple differential cross sections (TDCS) by the application of the laser field. Numerical results show that the TDCS are strongly dependent on the dressing of the projectile by the laser field at low frequency in (e, 2e) spectroscopy region.

Ultraviolet surprise: Efficient soft x-ray high-harmonic generation in multiply ionized plasmas.

PubMed

Popmintchev, Dimitar; Hernández-García, Carlos; Dollar, Franklin; Mancuso, Christopher; Pérez-Hernández, Jose A; Chen, Ming-Chang; Hankla, Amelia; Gao, Xiaohui; Shim, Bonggu; Gaeta, Alexander L; Tarazkar, Maryam; Romanov, Dmitri A; Levis, Robert J; Gaffney, Jim A; Foord, Mark; Libby, Stephen B; Jaron-Becker, Agnieszka; Becker, Andreas; Plaja, Luis; Murnane, Margaret M; Kapteyn, Henry C; Popmintchev, Tenio

2015-12-04

High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Because of reduced quantum diffusion of the radiating electron wave function, the emission from each species is highest when a short-wavelength ultraviolet driving laser is used. However, phase matching--the constructive addition of x-ray waves from a large number of atoms--favors longer-wavelength mid-infrared lasers. We identified a regime of high-harmonic generation driven by 40-cycle ultraviolet lasers in waveguides that can generate bright beams in the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed harmonics with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth-limited pulse trains of ~100 attoseconds. Copyright © 2015, American Association for the Advancement of Science.

Quantum noise limits to matter-wave interferometry

NASA Technical Reports Server (NTRS)

Scully, Marlan O.; Dowling, Jonathan P.

1994-01-01

We derive the quantum limits for an atomic interferometer in which the atoms obey either Bose-Einstein or Fermi-Dirac statistics. It is found that the limiting quantum noise is due to the uncertainty associated with the particle sorting between the two branches of the interferometer. As an example, the quantum-limited sensitivity of a matter-wave gyroscope is calculated and compared with that of laser gyroscopes.

Creating Rydberg electron wave packets using terahertz pulses

NASA Astrophysics Data System (ADS)

Bromage, Jake

1999-10-01

In this thesis I present experiments in which we excited classical-limit states of an atom using terahertz pulses. In a classical-limit state, an atom's outer electron is confined to a wave packet that orbits the core along a classical trajectory. Researchers have excited states with classical traits, but wave packets localized in all three dimensions have proved elusive. Theoretical studies have shown such states can be created using terahertz pulses. Using these techniques, we created a linear-orbit wave packet (LOWP), that is three-dimensionally localized and orbits along a line on one side of the atom's core. Terahertz pulses are sub-picosecond bursts of far- infrared radiation. Unlike ultrashort optical pulses, the electric field of terahertz pulses barely completes a single cycle. Our simulations of the atom-pulse interaction show that this electric field profile is critical in determining the quality of the wave packet. To characterize our terahertz pulses, we invented dithered-edge sampling which time- resolves the electric field using a photoconductive receiver and a triggered attenuator. We also studied how pulses are distorted after propagating through metallic structures, and used our findings to design our atomic experiments. We excited wave packets in atomic sodium using a two-step process. First, we used tunable, nanosecond dye lasers to excite an extreme Stark state. Next, we used a terahertz pump pulse to coherently redistribute population among extreme Stark states in neighboring manifolds. Interference between the final states produces a localized, dynamic LOWP. To analyze the LOWP, we ionized it with a stronger terahertz probe pulse, varying the pump-probe delay to map out its motion. We observed two strong LOWP signatures. Changing the static electric field produced small changes (2%) in the orbital period that agreed with our theoretical predictions. Secondly, because the LOWP scatters off the core, the pump-probe signal depended on the direction of the kick the LOWP received from the robe pulse. These observations, combined with our detailed simulations that used sodium parameters and the actual shape of the terahertz pulse, lead us to conclude that we excited a LOWP.

Underground atom gradiometer array for mass distribution monitoring and advanced geodesy

NASA Astrophysics Data System (ADS)

Canuel, B.

2015-12-01

After more than 20 years of fundamental research, atom interferometers have reached sensitivity and accuracy levels competing with or beating inertial sensors based on different technologies. Atom interferometers offer interesting applications in geophysics (gravimetry, gradiometry, Earth rotation rate measurements), inertial sensing (submarine or aircraft autonomous positioning), metrology (new definition of the kilogram) and fundamental physics (tests of the standard model, tests of general relativity). Atom interferometers already contributed significantly to fundamental physics by, for example, providing stringent constraints on quantum-electrodynamics through measurements of the hyperfine structure constant, testing the Equivalence Principle with cold atoms, or providing new measurements for the Newtonian gravitational constant. Cold atom sensors have moreover been established as key instruments in metrology for the new definition of the kilogram or through international comparisons of gravimeters. The field of atom interferometry (AI) is now entering a new phase where very high sensitivity levels must be demonstrated, in order to enlarge the potential applications outside atomic physics laboratories. These applications range from gravitational wave (GW) detection in the [0.1-10 Hz] frequency band to next generation ground and space-based Earth gravity field studies to precision gyroscopes and accelerometers. The Matter-wave laser Interferometric Gravitation Antenna (MIGA) presented here is a large-scale matter-wave sensor which will open new applications in geoscience and fundamental physics. The MIGA consortium gathers 18 expert French laboratories and companies in atomic physics, metrology, optics, geosciences and gravitational physics, with the aim to build a large-scale underground atom-interferometer instrument by 2018 and operate it till at least 2023. In this paper, we present the main objectives of the project, the status of the construction of the instrument and the motivation for the applications of MIGA in geosciences

The fractal geometry of Hartree-Fock

NASA Astrophysics Data System (ADS)

Theel, Friethjof; Karamatskou, Antonia; Santra, Robin

2017-12-01

The Hartree-Fock method is an important approximation for the ground-state electronic wave function of atoms and molecules so that its usage is widespread in computational chemistry and physics. The Hartree-Fock method is an iterative procedure in which the electronic wave functions of the occupied orbitals are determined. The set of functions found in one step builds the basis for the next iteration step. In this work, we interpret the Hartree-Fock method as a dynamical system since dynamical systems are iterations where iteration steps represent the time development of the system, as encountered in the theory of fractals. The focus is put on the convergence behavior of the dynamical system as a function of a suitable control parameter. In our case, a complex parameter λ controls the strength of the electron-electron interaction. An investigation of the convergence behavior depending on the parameter λ is performed for helium, neon, and argon. We observe fractal structures in the complex λ-plane, which resemble the well-known Mandelbrot set, determine their fractal dimension, and find that with increasing nuclear charge, the fragmentation increases as well.

Quantum primary rainbows in transmission of positrons through very short carbon nanotubes

NASA Astrophysics Data System (ADS)

Ćosić, M.; Petrović, S.; Nešković, N.

2016-04-01

This paper is devoted to a quantum mechanical consideration of the transmission of positrons of a kinetic energy of 1 MeV through very short (11, 9) single-wall chiral carbon nanotubes. The nanotube lengths are between 50 and 320 nm. The transmission process is determined by the rainbow effects. The interaction potential of a positron and the nanotube is deduced from the Molire's interaction potential of the positron and a nanotube atom using the continuum approximation. We solve numerically the time-dependent Schrödinger equation, and calculate the spatial and angular distributions of transmitted positrons. The initial positron beam is assumed to be an ensemble of non-interacting Gaussian wave packets. We generate the spatial and angular distributions using the computer simulation method. The examination is focused on the spatial and angular primary rainbows. It begins with an analysis of the corresponding classical rainbows, and continues with a detailed investigation of the amplitudes and phases of the wave functions of transmitted positrons. These analyses enable one to identify the principal and supernumerary primary rainbows appearing in the spatial and angular distributions. They also result in a detailed explanation of the way of their generation, which includes the effects of wrinkling of each wave packet during its deflection from the nanotube wall, and of its concentration just before a virtual barrier lying close to the corresponding classical rainbow. The wrinkling of the wave packets occurs due to their internal focusing. In addition, the wave packets wrinkle in a mutually coordinated way. This explanation may induce new theoretical and experimental investigations of quantum rainbows occurring in various atomic collision processes.

Edge reconstruction in armchair phosphorene nanoribbons revealed by discontinuous Galerkin density functional theory.

PubMed

Hu, Wei; Lin, Lin; Yang, Chao

2015-12-21

With the help of our recently developed massively parallel DGDFT (Discontinuous Galerkin Density Functional Theory) methodology, we perform large-scale Kohn-Sham density functional theory calculations on phosphorene nanoribbons with armchair edges (ACPNRs) containing a few thousands to ten thousand atoms. The use of DGDFT allows us to systematically achieve a conventional plane wave basis set type of accuracy, but with a much smaller number (about 15) of adaptive local basis (ALB) functions per atom for this system. The relatively small number of degrees of freedom required to represent the Kohn-Sham Hamiltonian, together with the use of the pole expansion the selected inversion (PEXSI) technique that circumvents the need to diagonalize the Hamiltonian, results in a highly efficient and scalable computational scheme for analyzing the electronic structures of ACPNRs as well as their dynamics. The total wall clock time for calculating the electronic structures of large-scale ACPNRs containing 1080-10,800 atoms is only 10-25 s per self-consistent field (SCF) iteration, with accuracy fully comparable to that obtained from conventional planewave DFT calculations. For the ACPNR system, we observe that the DGDFT methodology can scale to 5000-50,000 processors. We use DGDFT based ab initio molecular dynamics (AIMD) calculations to study the thermodynamic stability of ACPNRs. Our calculations reveal that a 2 × 1 edge reconstruction appears in ACPNRs at room temperature.

The Mystery of Matter, World of the Atom Series.

ERIC Educational Resources Information Center

Pollard, William G.

This booklet is one in the "World of the Atome Series" for junior high school students and their teachers. It describes the fascinating story of the search for the key to the structure of matter. These topics are reviewed: the chemical atom of the 19th century, the planetary atom, the wave atom, inside the elementary particles, and the mystery of…

High-precision two-dimensional atom localization from four-wave mixing in a double-Λ four-level atomic system

NASA Astrophysics Data System (ADS)

Shui, Tao; Yang, Wen-Xing; Chen, Ai-Xi; Liu, Shaopeng; Li, Ling; Zhu, Zhonghu

2018-03-01

We propose a scheme for high-precision two-dimensional (2D) atom localization via the four-wave mixing (FWM) in a four-level double-Λ atomic system. Due to the position-dependent atom-field interaction, the 2D position information of the atoms can be directly determined by the measurement of the normalized light intensity of output FWM-generated field. We further show that, when the position-dependent generated FWM field has become sufficiently intense, efficient back-coupling to the FWM generating state becomes important. This back-coupling pathway leads to competitive multiphoton destructive interference of the FWM generating state by three supplied and one internally generated fields. We find that the precision of 2D atom localization can be improved significantly by the multiphoton destructive interference and depends sensitively on the frequency detunings and the pump field intensity. Interestingly enough, we show that adjusting the frequency detunings and the pump field intensity can modify significantly the FWM efficiency, and consequently lead to a redistribution of the atoms. As a result, the atom can be localized in one of four quadrants with holding the precision of atom localization.

Cw hyper-Raman laser and four-wave mixing in atomic sodium

NASA Astrophysics Data System (ADS)

Klug, M.; Kablukov, S. I.; Wellegehausen, B.

2005-01-01

Continuous wave hyper-Raman (HR) generation in a ring cavity on the 6s → 4p transition at 1640 nm in sodium is realized for the first time by two-photon excitation of atomic sodium on the 3s → 6s transition with a continuous wave (cw) dye laser at 590 nm and a single frequency argon ion laser at 514 nm. It is shown, that the direction and efficiency of HR lasing depends on the propagation direction of the pump waves and their frequencies. More than 30% HR gain is measured at 250 mW of pump laser powers for counter-propagating pump waves and a medium length of 90 mm. For much shorter interaction lengths and corresponding focussing of the pump waves a dramatic increase of the gain is predicted. For co-propagating pump waves, in addition, generation of 330 nm radiation on the 4p → 3s transition by a four-wave mixing (FWM) process is observed. Dependencies of HR and parametric four-wave generation have been investigated and will be discussed.

Attosecond transient absorption of a bound wave packet coupled to a smooth continuum

DOE PAGES

Dahlström, Jan Marcus; Pabst, Stefan; Lindroth, Eva

2017-10-16

Here, we investigate the possibility of using transient absorption of a coherent bound electron wave packet in hydrogen as an attosecond pulse characterization technique. In a recent work, we have shown that photoionization of such a coherent bound electron wave packet opens up for pulse characterization with unprecedented temporal accuracy—independent of the atomic structure—with maximal photoemission at all kinetic energies given a wave packet with zero relative phase. Here, we perform numerical propagation of the time-dependent Schrödinger equation and analytical calculations based on perturbation theory to show that the energy-resolved maximal absorption of photons from the attosecond pulse does not uniquely occur at a zero relative phase of the initial wave packet. Instead, maximal absorption occurs at different relative wave packet phases, distributed as a non-monotonous function with a smoothmore » $$-\\pi /2$$ shift across the central photon energy (given a Fourier-limited Gaussian pulse). Similar results are also found in helium. Our finding is surprising, because it implies that the energy-resolved photoelectrons are not mapped one-to-one with the energy-resolved absorbed photons of the attosecond pulse.« less

Attosecond transient absorption of a bound wave packet coupled to a smooth continuum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahlström, Jan Marcus; Pabst, Stefan; Lindroth, Eva

Here, we investigate the possibility of using transient absorption of a coherent bound electron wave packet in hydrogen as an attosecond pulse characterization technique. In a recent work, we have shown that photoionization of such a coherent bound electron wave packet opens up for pulse characterization with unprecedented temporal accuracy—independent of the atomic structure—with maximal photoemission at all kinetic energies given a wave packet with zero relative phase. Here, we perform numerical propagation of the time-dependent Schrödinger equation and analytical calculations based on perturbation theory to show that the energy-resolved maximal absorption of photons from the attosecond pulse does not uniquely occur at a zero relative phase of the initial wave packet. Instead, maximal absorption occurs at different relative wave packet phases, distributed as a non-monotonous function with a smoothmore » $$-\\pi /2$$ shift across the central photon energy (given a Fourier-limited Gaussian pulse). Similar results are also found in helium. Our finding is surprising, because it implies that the energy-resolved photoelectrons are not mapped one-to-one with the energy-resolved absorbed photons of the attosecond pulse.« less

Study of the low energy spectrum of titanium by using QMC methods

NASA Astrophysics Data System (ADS)

Buendía, E.; Caballero, M. A.; Gálvez, F. J.

2018-02-01

We study the ground state and the low energy excited states of Ti. Each variational wave function is a product of a Jastrow correlation factor by a model function obtained within the parameterized optimized effective potential (POEP) framework by using a configuration mixing. Near degeneracy effects between the orbitals 4s and 4p, as well as excitations to the 3d orbital due to the strong competition between 4s and 3d orbitals in transition metal atoms are taken into account. All electron calculations have been carried out by using quantum Monte Carlo techniques, variational and diffusion.

Fast, externally triggered, digital phase controller for an optical lattice

NASA Astrophysics Data System (ADS)

Sadgrove, Mark; Nakagawa, Ken'ichi

2011-11-01

We present a method to control the phase of an optical lattice according to an external trigger signal. The method has a latency of less than 30 μs. Two phase locked digital synthesizers provide the driving signal for two acousto-optic modulators which control the frequency and phase of the counter-propagating beams which form a standing wave (optical lattice). A micro-controller with an external interrupt function is connected to the desired external signal, and updates the phase register of one of the synthesizers when the external signal changes. The standing wave (period λ/2 = 390 nm) can be moved by units of 49 nm with a mean jitter of 28 nm. The phase change is well known due to the digital nature of the synthesizer, and does not need calibration. The uses of the scheme include coherent control of atomic matter-wave dynamics.

Applying Molecular Bonding Concepts to the Solid State

NASA Astrophysics Data System (ADS)

Dunnington, Benjamin D.

In this thesis, we describe the extension and application of Natural Bond Orbital (NBO) analysis to periodic systems. This enables the translation of rigorous, quantum mechanical calculation results of solid systems into the localized lone pairs and two-center bonds of Lewis structures. Such localized bonding descriptions form the basic language of chemistry, and application of these ideas to solids allows for the understanding of complex phenomena in bulk systems using readily accessible concepts from molecular science. In addition to the algorithmic adjustments needed for to account for periodic boundary conditions in the NBO process, we also discuss methodology to interface the ubiquitous plane wave basis sets of the solid state with the atom-centered basis functions needed as input for NBO analysis. We will describe one method using projection of the plane wave eigenstates, and a second projection-free method that involves the direct calculation of matrix elements of the plane wave Hamiltonian in an atom-centered basis. The reliance of many localized, post-computational analysis techniques on an atom-centered description of the orbitals, means these interfaces will have applicability beyond our NBO development. An ideal area for application of such molecular descriptions of periodic systems is heterogeneous catalysis, where reactants from a gas/liquid phase react on a solid catalyst surface. Previous studies of these systems have originated from the delocalized perspective of the bulk catalyst. NBO provides an explicit description of the perturbative effect of the catalyst on the covalent bonds of the reactant, which is correlated with the catalytic activity of the material. Such a shift to an adsorbate focused description of surface reactivity will enable understanding of catalysis across a variety of materials.

Subwavelength atom localization via coherent manipulation of the Raman gain process

NASA Astrophysics Data System (ADS)

Qamar, Sajid; Mehmood, Asad; Qamar, Shahid

2009-03-01

We present a simple scheme of atom localization in a subwavelength domain via manipulation of Raman gain process. We consider a four-level system with a pump and a weak probe field. In addition, we apply a coherent field to control the gain process. The system is similar to the one used by Agarwal and Dasgupta [Phys. Rev. A 70, 023802 (2004)] for the superluminal pulse propagation through Raman gain medium. For atom localization, we consider both pump and control fields to be the standing-wave fields of the cavity. We show that a much precise position of an atom passing through the standing-wave fields can be determined by measuring the gain spectrum of the probe field.

Evidence for unnatural-parity contributions to electron-impact ionization of laser-aligned atoms

DOE PAGES

Armstrong, Gregory S. J.; Colgan, James Patrick; Pindzola, M. S.; ...

2015-09-11

Recent measurements have examined the electron-impact ionization of excited-state laser-aligned Mg atoms. In this paper we show that the ionization cross section arising from the geometry where the aligned atom is perpendicular to the scattering plane directly probes the unnatural parity contributions to the ionization amplitude. The contributions from natural parity partial waves cancel exactly in this geometry. Our calculations resolve the discrepancy between the nonzero measured cross sections in this plane and the zero cross section predicted by distorted-wave approaches. Finally, we demonstrate that this is a general feature of ionization from p-state targets by additional studies of ionizationmore » from excited Ca and Na atoms.« less

Atom Interferometry

ScienceCinema

Kasevich, Mark

2017-12-22

Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

Atom Interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasevich, Mark

2008-05-07

Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Canmore » atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?« less

Regular and Chaotic Spatial Distribution of Bose-Einstein Condensed Atoms in a Ratchet Potential

NASA Astrophysics Data System (ADS)

Li, Fei; Xu, Lan; Li, Wenwu

2018-02-01

We study the regular and chaotic spatial distribution of Bose-Einstein condensed atoms with a space-dependent nonlinear interaction in a ratchet potential. There exists in the system a space-dependent atomic current that can be tuned via Feshbach resonance technique. In the presence of the space-dependent atomic current and a weak ratchet potential, the Smale-horseshoe chaos is studied and the Melnikov chaotic criterion is obtained. Numerical simulations show that the ratio between the intensities of optical potentials forming the ratchet potential, the wave vector of the laser producing the ratchet potential or the wave vector of the modulating laser can be chosen as the controlling parameters to result in or avoid chaotic spatial distributional states.

EPRB Gedankenexperiment and Entanglement with Classical Light Waves

NASA Astrophysics Data System (ADS)

Rashkovskiy, Sergey A.

2018-06-01

In this article we show that results similar to those of the Einstein-Podolsky-Rosen-Bohm (EPRB) Gedankenexperiment and entanglement of photons can be obtained using weak classical light waves if we take into account the discrete (atomic) structure of the detectors and a specific nature of the light-atom interaction. We show that the CHSH (Clauser, Horne, Shimony, and Holt) criterion in the EPRB Gedankenexperiment with classical light waves can exceed not only the maximum value SHV=2 that is predicted by the local hidden-variable theories but also the maximum value S_{QM} = 2√2 predicted by quantum mechanics.

Single photon at a configurable quantum-memory-based beam splitter

NASA Astrophysics Data System (ADS)

Guo, Xianxin; Mei, Yefeng; Du, Shengwang

2018-06-01

We report the demonstration of a configurable coherent quantum-memory-based beam splitter (BS) for a single-photon wave packet making use of laser-cooled 85Rb atoms and electromagnetically induced transparency. The single-photon wave packet is converted (stored) into a collective atomic spin state and later retrieved (split) into two nearly opposing directions. The storage time, beam-splitting ratio, and relative phase are configurable and can be dynamically controlled. We experimentally confirm that such a BS preserves the quantum particle nature of the single photon and the coherence between the two split wave packets of the single photon.

Electromagnetically-induced-absorption resonance with high contrast and narrow width in the Hanle configuration

NASA Astrophysics Data System (ADS)

Brazhnikov, D. V.; Taichenachev, A. V.; Tumaikin, A. M.; Yudin, V. I.

2014-12-01

The method for observing the high-contrast and narrow-width resonances of electromagnetically induced absorption (EIA) in the Hanle configuration under counter-propagating pump and probe light waves is proposed. Here, as an example, we study a ‘dark’ type of atomic dipole transition {{F}\\text{g}}={1}\\to {{F}\\text{e}}={1} in D1 line of 87Rb, where usually the electromagnetically induced transparency can be observed. To obtain the EIA signal one should properly choose the polarizations of light waves and intensities. In contrast to regular schemes for observing EIA signals (under a single traveling light wave in the Hanle configuration or under a bichromatic light field consisting of two traveling waves), the proposed scheme allows one to use buffer gas for significantly improving the properties of the resonance. Also the dramatic influence of atomic transition openness on the contrast of the resonance is revealed, which is advantageous in comparison with cyclic atomic transitions. The nonlinear resonances in a probe-wave transmitted signal with contrast close to 100% and sub-kHz widths can be obtained. The results are interesting in high-resolution spectroscopy, nonlinear and magneto-optics.

Particle energy distributions and metastable atoms in transient low pressure interpulse microwave plasma

NASA Astrophysics Data System (ADS)

Pandey, Shail; Nath Patel, Dudh; Ram Baitha, Anuj; Bhattacharjee, Sudeep

2015-12-01

The electron energies and its distribution function are measured in non-equilibrium transient pulsed microwave plasmas in the interpulse regime using a retarding field electron energy analyzer. The plasmas are driven to different initial conditions by varying the electromagnetic (EM) wave pulse duration, peak power, or the wave frequency. Two cases of wave excitation are investigated: (i) short-pulse (pulse duration, t w ~ 1 μs), high-power (~60 kW) waves of 9.45 GHz and (ii) medium-pulse (t w ~ 20 μs), and moderate power waves of ~3 kW at 2.45 GHz. It is found that high-power, short-duration pulses lead to a significantly different electron energy probability function (EEPF) in the interpulse phase—a Maxwellian with a bump on the tail, although the average energy per pulse (~60 mJ) is maintained the same in the two modes of wave excitation. Electrons with energies  >250 eV are found to exist in the discharge in the both cases. Another subset of experiments is performed to delineate the effect of the wave frequency and the peak power on EEPF. A traveling wave tube (TWT) amplifier based microwave source for generating pulsed plasma (t w  =  230 μs) in a wide frequency range (6-18 GHz) is employed for this purpose. Further experiments on measurements of metastable density using optical emission spectroscopy and ion energy analyzer have been carried out. By tailoring the EEPF of the transient plasma and metastable densities, new applications in plasma processing, chemistry and biology can be realized in the interpulse phase of the discharge.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doma, S. B., E-mail: sbdoma@alexu.edu.eg; Shaker, M. O.; Farag, A. M.

The variational Monte Carlo method is applied to investigate the ground state and some excited states of the lithium atom and its ions up to Z = 10 in the presence of an external magnetic field regime with γ = 0–100 arb. units. The effect of increasing field strength on the ground state energy is studied and precise values for the crossover field strengths were obtained. Our calculations are based on using accurate forms of trial wave functions, which were put forward in calculating energies in the absence of magnetic field. Furthermore, the value of Y at which ground-state energymore » of the lithium atom approaches to zero was calculated. The obtained results are in good agreement with the most recent values and also with the exact values.« less

Laser-ranging long-baseline differential atom interferometers for space

NASA Astrophysics Data System (ADS)

Chiow, Sheng-wey; Williams, Jason; Yu, Nan

2015-12-01

High-sensitivity differential atom interferometers (AIs) are promising for precision measurements in science frontiers in space, including gravity-field mapping for Earth science studies and gravitational wave detection. Difficulties associated with implementing long-baseline differential AIs have previously included the need for a high optical power, large differential Doppler shifts, and narrow dynamic range. We propose a configuration of twin AIs connected by a laser-ranging interferometer (LRI-AI) to provide precise information of the displacements between the two AI reference mirrors and also to phase-lock the two independent interferometer lasers over long distances, thereby drastically improving the practical feasibility of long-baseline differential AI measurements. We show that a properly implemented LRI-AI can achieve equivalent functionality to the conventional differential AI measurement configuration.

The physics of interstellar shock waves

NASA Technical Reports Server (NTRS)

Shull, J. Michael; Draine, Bruce T.

1987-01-01

This review discusses the observations and theoretical models of interstellar shock waves, in both diffuse cloud and molecular cloud environments. It summarizes the relevant gas dynamics, atomic, molecular and grain processes, radiative transfer, and physics of radiative and magnetic precursors in shock models. It then describes the importance of shocks for observations, diagnostics, and global interstellar dynamics. It concludes with current research problems and data needs for atomic, molecular and grain physics.

Quasi Sturmian basis for the two-electon continuum

NASA Astrophysics Data System (ADS)

Zaytsev, A. S.; Ancarani, L. U.; Zaytsev, S. A.

2016-02-01

A new type of basis functions is proposed to describe a two-electron continuum which arises as a final state in electron-impact ionization and double photoionization of atomic systems. We name these functions, which are calculated in terms of the recently introduced quasi Sturmian functions, Convoluted Quasi Sturmian functions (CQS); by construction, they look asymptotically like a six-dimensional spherical wave. The driven equation describing an ( e, 3 e) process on helium in the framework of the Temkin-Poet model is solved numerically in the entire space (rather than in a finite region of space) using expansions on CQS basis functions. We show that quite rapid convergence of the solution expansion can be achieved by multiplying the basis functions by the logarithmic phase factor corresponding to the Coulomb electron-electron interaction.

Spin-orbital quantum liquid on the honeycomb lattice

NASA Astrophysics Data System (ADS)

Corboz, Philippe

2013-03-01

The symmetric Kugel-Khomskii can be seen as a minimal model describing the interactions between spin and orbital degrees of freedom in transition-metal oxides with orbital degeneracy, and it is equivalent to the SU(4) Heisenberg model of four-color fermionic atoms. We present simulation results for this model on various two-dimensional lattices obtained with infinite projected-entangled pair states (iPEPS), an efficient variational tensor-network ansatz for two dimensional wave functions in the thermodynamic limit. This approach can be seen as a two-dimensional generalization of matrix product states - the underlying ansatz of the density matrix renormalization group method. We find a rich variety of exotic phases: while on the square and checkerboard lattices the ground state exhibits dimer-Néel order and plaquette order, respectively, quantum fluctuations on the honeycomb lattice destroy any order, giving rise to a spin-orbital liquid. Our results are supported from flavor-wave theory and exact diagonalization. Furthermore, the properties of the spin-orbital liquid state on the honeycomb lattice are accurately accounted for by a projected variational wave-function based on the pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the ground state is an algebraic spin-orbital liquid. This model provides a good starting point to understand the recently discovered spin-orbital liquid behavior of Ba3CuSb2O9. The present results also suggest to choose optical lattices with honeycomb geometry in the search for quantum liquids in ultra-cold four-color fermionic atoms. We acknowledge the financial support from the Swiss National Science Foundation.

Ultracold collisions between Rb atoms and a Sr+ ion

NASA Astrophysics Data System (ADS)

Meir, Ziv; Sikorsky, Tomas; Ben-Shlomi, Ruti; Dallal, Yehonatan; Ozeri, Roee

2015-05-01

In last decade, a novel field emerged, in which ultracold atoms and ions in overlapping traps are brought into interaction. In contrast to the short ranged atom-atom interaction which scales as r-6, atom-ion potential persists for hundreds of μm's due to its lower power-law scaling - r-4. Inelastic collisions between the consistuents lead to spin and charge transfer and also to molecule formation. Elastic collisions control the energy transfer between the ion and the atoms. The study of collisions at the μK range has thus far been impeded by the effect of the ion's micromotion which limited collision energy to mK scale. Unraveling this limit will allow to investigate few partial wave and even S-wave collisions. Our system is capable of trapping Sr+ ions and Rb and Sr atoms and cooling them to their quantum ground state. Atoms and ions are trapped and cooled in separate chambers. Then, the atoms are transported using an optical conveyer belt to overlap the ions. In contrast to other experiments in this field where the atoms are used to sympathetic cool the ion, our system is also capable of ground state cooling the ion before immersing it into the atom cloud. By this method, we would be able to explore heating and cooling dynamics in the ultracold regime.

Highly retrievable spin-wave-photon entanglement source.

PubMed

Yang, Sheng-Jun; Wang, Xu-Jie; Li, Jun; Rui, Jun; Bao, Xiao-Hui; Pan, Jian-Wei

2015-05-29

Entanglement between a single photon and a quantum memory forms the building blocks for a quantum repeater and quantum network. Previous entanglement sources are typically with low retrieval efficiency, which limits future larger-scale applications. Here, we report a source of highly retrievable spin-wave-photon entanglement. Polarization entanglement is created through interaction of a single photon with an ensemble of atoms inside a low-finesse ring cavity. The cavity is engineered to be resonant for dual spin-wave modes, which thus enables efficient retrieval of the spin-wave qubit. An intrinsic retrieval efficiency up to 76(4)% has been observed. Such a highly retrievable atom-photon entanglement source will be very useful in future larger-scale quantum repeater and quantum network applications.

Impact of Alloy Fluctuations on Radiative and Auger Recombination in InGaN Quantum Wells

NASA Astrophysics Data System (ADS)

Jones, Christina; Teng, Chu-Hsiang; Yan, Qimin; Ku, Pei-Cheng; Kioupakis, Emmanouil

Light-emitting diodes (LEDs) based on indium gallium nitride (InGaN) are important for efficient solid-state lighting (2014 Nobel Prize in Physics). Despite its many successes, InGaN suffers from issues that reduce the efficiency of devices at high power, such as the green gap and efficiency droop. The origin of the droop has been attributed to Auger recombination, mediated by carrier scattering due to phonons and alloy disorder. Additionally, InGaN exhibits atomic-scale composition fluctuations that localize carriers and may affect the efficiency. In this work, we study the effect of local composition fluctuations on the radiative recombination rate, Auger recombination rate, and efficiency of InGaN/GaN quantum wells. We apply k.p calculations to simulate band edges and wave functions of quantum wells with fluctuating alloy distributions based on atom probe tomography data, and we evaluate double and triple overlaps of electron and hole wave functions. We compare results for quantum wells with fluctuating alloy distributions to those with uniform alloy compositions and to published work. Our results demonstrate that alloy-composition fluctuations aggravate the efficiency-droop and green-gap problems and further reduce LED efficiency at high power. We acknowledge the NSF CAREER award DMR-1254314, the NSF Graduate Research Fellowship Program DGE-1256260, and the DOE NERSC facility (DE-AC02-05CH11231).

Laser wavelength effect on charge transfer and excitation processes in laser-assisted collisions of Li+ + H

NASA Astrophysics Data System (ADS)

Domínguez-Gutiérrez, F. Javier; Cabrera-Trujillo, R.

2014-05-01

Total, n = 2 , and 3 charge transfer and n = 2 target excitation probabilities for collision of Li+ with ground state atomic hydrogen are calculated numerically, in the impact energy collision range 0.25-5 keV. The total wave function at the end of the dynamics of the collision is obtained by solving the time-dependent Schrödinger equation by means the finite-difference method. We use a pseudo-potential method to model the electronic structure of the Li+ ion. The n = 2 , and 3 charge transfer and n = 2 target excitation probabilities are obtained by projecting the stationary states of Lithium and Hydrogen neutral atoms to the total wave function of the collision, respectively; the stationary states of Li and H are obtained numerically. To assess the validity of our method, our numerical results have been compared with those obtained experimentally and by other theoretical methods found in the literature. We study the laser-assited collision by using a short (3 fs at FWHM) and intense (3.15 ×12 W/cm2) Gaussian laser pulse. We consider a wavelength range between 400 - 1000 nm in steps of 100 nm. Finally, we analyze the laser assisted collision by a qualitatively way with a two level approach. We acknowledge support from grant PAPIIT IN 110-714 and CONACyT (Ph.D. scholarship).

Basis set limit and systematic errors in local-orbital based all-electron DFT

NASA Astrophysics Data System (ADS)

Blum, Volker; Behler, Jörg; Gehrke, Ralf; Reuter, Karsten; Scheffler, Matthias

2006-03-01

With the advent of efficient integration schemes,^1,2 numeric atom-centered orbitals (NAO's) are an attractive basis choice in practical density functional theory (DFT) calculations of nanostructured systems (surfaces, clusters, molecules). Though all-electron, the efficiency of practical implementations promises to be on par with the best plane-wave pseudopotential codes, while having a noticeably higher accuracy if required: Minimal-sized effective tight-binding like calculations and chemically accurate all-electron calculations are both possible within the same framework; non-periodic and periodic systems can be treated on equal footing; and the localized nature of the basis allows in principle for O(N)-like scaling. However, converging an observable with respect to the basis set is less straightforward than with competing systematic basis choices (e.g., plane waves). We here investigate the basis set limit of optimized NAO basis sets in all-electron calculations, using as examples small molecules and clusters (N2, Cu2, Cu4, Cu10). meV-level total energy convergence is possible using <=50 basis functions per atom in all cases. We also find a clear correlation between the errors which arise from underconverged basis sets, and the system geometry (interatomic distance). ^1 B. Delley, J. Chem. Phys. 92, 508 (1990), ^2 J.M. Soler et al., J. Phys.: Condens. Matter 14, 2745 (2002).

Phonon Transport at the Interfaces of Vertically Stacked Graphene and Hexagonal Boron Nitride Heterostructures

DOE PAGES

Yan, Zhequan; Chen, Liang; Yoon, Mina; ...

2016-01-12

Hexagonal boron nitride (h-BN) is a substrate for graphene based nano-electronic devices. We investigate the ballistic phonon transport at the interface of vertically stacked graphene and h-BN heterostructures using first principles density functional theory and atomistic Green's function simulations considering the influence of lattice stacking. We compute the frequency and wave-vector dependent transmission function and observe distinct stacking-dependent phonon transmission features for the h-BN/graphene/h-BN sandwiched systems. We find that the in-plane acoustic modes have the dominant contributions to the phonon transmission and thermal boundary conductance (TBC) for the interfaces with the carbon atom located directly on top of the boronmore » atom (C–B matched) because of low interfacial spacing. The low interfacial spacing is a consequence of the differences in the effective atomic volume of N and B and the difference in the local electron density around N and B. For the structures with the carbon atom directly on top of the nitrogen atom (C–N matched), the spatial distance increases and the contribution of in-plane modes to the TBC decreases leading to higher contributions by out-of-plane acoustic modes. We find that the C–B matched interfaces have stronger phonon–phonon coupling than the C–N matched interfaces, which results in significantly higher TBC (more than 50%) in the C–B matched interface. The findings in this study will provide insights to understand the mechanism of phonon transport at h-BN/graphene/h-BN interfaces, to better explain the experimental observations and to engineer these interfaces to enhance heat dissipation in graphene based electronic devices.« less

A new near-linear scaling, efficient and accurate, open-shell domain-based local pair natural orbital coupled cluster singles and doubles theory.

PubMed

Saitow, Masaaki; Becker, Ute; Riplinger, Christoph; Valeev, Edward F; Neese, Frank

2017-04-28

The Coupled-Cluster expansion, truncated after single and double excitations (CCSD), provides accurate and reliable molecular electronic wave functions and energies for many molecular systems around their equilibrium geometries. However, the high computational cost, which is well-known to scale as O(N 6 ) with system size N, has limited its practical application to small systems consisting of not more than approximately 20-30 atoms. To overcome these limitations, low-order scaling approximations to CCSD have been intensively investigated over the past few years. In our previous work, we have shown that by combining the pair natural orbital (PNO) approach and the concept of orbital domains it is possible to achieve fully linear scaling CC implementations (DLPNO-CCSD and DLPNO-CCSD(T)) that recover around 99.9% of the total correlation energy [C. Riplinger et al., J. Chem. Phys. 144, 024109 (2016)]. The production level implementations of the DLPNO-CCSD and DLPNO-CCSD(T) methods were shown to be applicable to realistic systems composed of a few hundred atoms in a routine, black-box fashion on relatively modest hardware. In 2011, a reduced-scaling CCSD approach for high-spin open-shell unrestricted Hartree-Fock reference wave functions was proposed (UHF-LPNO-CCSD) [A. Hansen et al., J. Chem. Phys. 135, 214102 (2011)]. After a few years of experience with this method, a few shortcomings of UHF-LPNO-CCSD were noticed that required a redesign of the method, which is the subject of this paper. To this end, we employ the high-spin open-shell variant of the N-electron valence perturbation theory formalism to define the initial guess wave function, and consequently also the open-shell PNOs. The new PNO ansatz properly converges to the closed-shell limit since all truncations and approximations have been made in strict analogy to the closed-shell case. Furthermore, given the fact that the formalism uses a single set of orbitals, only a single PNO integral transformation is necessary, which offers large computational savings. We show that, with the default PNO truncation parameters, approximately 99.9% of the total CCSD correlation energy is recovered for open-shell species, which is comparable to the performance of the method for closed-shells. UHF-DLPNO-CCSD shows a linear scaling behavior for closed-shell systems, while linear to quadratic scaling is obtained for open-shell systems. The largest systems we have considered contain more than 500 atoms and feature more than 10 000 basis functions with a triple-ζ quality basis set.

A new near-linear scaling, efficient and accurate, open-shell domain-based local pair natural orbital coupled cluster singles and doubles theory

NASA Astrophysics Data System (ADS)

Saitow, Masaaki; Becker, Ute; Riplinger, Christoph; Valeev, Edward F.; Neese, Frank

2017-04-01

The Coupled-Cluster expansion, truncated after single and double excitations (CCSD), provides accurate and reliable molecular electronic wave functions and energies for many molecular systems around their equilibrium geometries. However, the high computational cost, which is well-known to scale as O(N6) with system size N, has limited its practical application to small systems consisting of not more than approximately 20-30 atoms. To overcome these limitations, low-order scaling approximations to CCSD have been intensively investigated over the past few years. In our previous work, we have shown that by combining the pair natural orbital (PNO) approach and the concept of orbital domains it is possible to achieve fully linear scaling CC implementations (DLPNO-CCSD and DLPNO-CCSD(T)) that recover around 99.9% of the total correlation energy [C. Riplinger et al., J. Chem. Phys. 144, 024109 (2016)]. The production level implementations of the DLPNO-CCSD and DLPNO-CCSD(T) methods were shown to be applicable to realistic systems composed of a few hundred atoms in a routine, black-box fashion on relatively modest hardware. In 2011, a reduced-scaling CCSD approach for high-spin open-shell unrestricted Hartree-Fock reference wave functions was proposed (UHF-LPNO-CCSD) [A. Hansen et al., J. Chem. Phys. 135, 214102 (2011)]. After a few years of experience with this method, a few shortcomings of UHF-LPNO-CCSD were noticed that required a redesign of the method, which is the subject of this paper. To this end, we employ the high-spin open-shell variant of the N-electron valence perturbation theory formalism to define the initial guess wave function, and consequently also the open-shell PNOs. The new PNO ansatz properly converges to the closed-shell limit since all truncations and approximations have been made in strict analogy to the closed-shell case. Furthermore, given the fact that the formalism uses a single set of orbitals, only a single PNO integral transformation is necessary, which offers large computational savings. We show that, with the default PNO truncation parameters, approximately 99.9% of the total CCSD correlation energy is recovered for open-shell species, which is comparable to the performance of the method for closed-shells. UHF-DLPNO-CCSD shows a linear scaling behavior for closed-shell systems, while linear to quadratic scaling is obtained for open-shell systems. The largest systems we have considered contain more than 500 atoms and feature more than 10 000 basis functions with a triple-ζ quality basis set.

Asymmetric angular dependence of spin-transfer torques in CoFe/Mg-B-O/CoFe magnetic tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Ling, E-mail: lingtang@zjut.edu.cn; Xu, Zhi-Jun, E-mail: xzj@zjut.edu.cn; Zuo, Xian-Jun

Using a first-principles noncollinear wave-function-matching method, we studied the spin-transfer torques (STTs) in CoFe/Mg-B-O/CoFe(001) magnetic tunnel junctions (MTJs), where three different types of B-doped MgO in the spacer are considered, including B atoms replacing Mg atoms (Mg{sub 3}BO{sub 4}), B atoms replacing O atoms (Mg{sub 4}BO{sub 3}), and B atoms occupying interstitial positions (Mg{sub 4}BO{sub 4}) in MgO. A strong asymmetric angular dependence of STT can be obtained both in ballistic CoFe/Mg{sub 3}BO{sub 4} and CoFe/Mg{sub 4}BO{sub 4} based MTJs, whereas a nearly symmetric STT curve is observed in the junctions based on CoFe/Mg{sub 4}BO{sub 3}. Furthermore, the asymmetry ofmore » the angular dependence of STT can be suppressed significantly by the disorder of B distribution. Such skewness of STTs in the CoFe/Mg-B-O/CoFe MTJs could be attributed to the interfacial resonance states induced by the B diffusion into MgO spacer.« less

Nonlinear reflection and refraction of ultrashort light pulses at the surfaces of resonant media and phase memory effects

NASA Astrophysics Data System (ADS)

Vlasov, R. A.; Gadomskii, O. H.; Gadomskaia, I. V.; Samartsev, V. V.

1986-06-01

The method of integrodifferential equations related to the optical Bloch equations is used to study the nonlinear reflection (or refraction) of a scanning laser beam at the surface of a resonant medium excited by traveling and standing surface electromagnetic waves at resonant frequency. The effect of the phase memory of surface atoms on the pulsed action of fields with space-time resolution is taken into account. The reversal of the scanning beam from the excited surface with phase conjugation of the wave front is considered. In addition, the spectrum of the nonlinear surface polaritons is analyzed as a function of the area of the exciting pulse and the penetration depth of polaritons in the resonant optical medium.

Invited article: Broadband highly-efficient dielectric metadevices for polarization control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.

Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. Furthermore, by employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-platesmore » that can operate across multiple telecom bands with ~99% polarization conversion efficiency.« less

Invited article: Broadband highly-efficient dielectric metadevices for polarization control

DOE PAGES

Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.; ...

2016-06-06

Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. Furthermore, by employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-platesmore » that can operate across multiple telecom bands with ~99% polarization conversion efficiency.« less

Method and apparatus for atomic imaging

DOEpatents

Saldin, Dilano K.; de Andres Rodriquez, Pedro L.

1993-01-01

A method and apparatus for three dimensional imaging of the atomic environment of disordered adsorbate atoms are disclosed. The method includes detecting and measuring the intensity of a diffuse low energy electron diffraction pattern formed by directing a beam of low energy electrons against the surface of a crystal. Data corresponding to reconstructed amplitudes of a wave form is generated by operating on the intensity data. The data corresponding to the reconstructed amplitudes is capable of being displayed as a three dimensional image of an adsorbate atom. The apparatus includes a source of a beam of low energy electrons and a detector for detecting the intensity distribution of a DLEED pattern formed at the detector when the beam of low energy electrons is directed onto the surface of a crystal. A device responsive to the intensity distribution generates a signal corresponding to the distribution which represents a reconstructed amplitude of a wave form and is capable of being converted into a three dimensional image of the atomic environment of an adsorbate atom on the crystal surface.

Quantum Statistical Properties of the Codirectional Kerr Nonlinear Coupler in Terms of su (2 ) Lie Group in Interaction with a Two-level Atom

NASA Astrophysics Data System (ADS)

Abdalla, M. Sebawe; Khalil, E. M.; Obada, A. S.-F.

2017-08-01

The problem of the codirectional Kerr coupler has been considered several times from different point of view. In the present paper we introduce the interaction between a two-level atom and the codirectional Kerr nonlinear coupler in terms of su (2 ) Lie algebra. Under certain conditions we have adjusted the Kerr coupler and consequently we have managed to handle the problem. The wave function is obtained by using the evolution operator where the Heisnberg equation of motion is invoked to get the constants of the motion. We note that the Kerr parameter χ as well as the quantum number j plays the role of controlling the atomic inversion behavior. Also the maximum entanglement occurs after a short period of time when χ = 0. On the other hand for the entropy and the variance squeezing we observe that there is exchange between the quadrature variances. Furthermore, the variation in the quantum number j as well as in the parameter χ leads to increase or decrease in the number of fluctuations. Finally we examined the second order correlation function where classical and nonclassical phenomena are observed.

Nonvariational calculation of the relativistic, finite-size, and QED corrections for the 2 1S excited state of the helium atom

NASA Astrophysics Data System (ADS)

Haftel, M. I.; Mandelzweig, V. B.

1994-05-01

Relativistic and QED corrections are calculated by using a direct solution of the Schrödinger equation for the 2 1S excited state of the helium atom obtained with the correlation-function hyperspherical-harmonic method. Our extremely accurate nonvariational results for relativistic, QED, and finite-size corrections coincide exactly (up to 0.000 03 cm-1) with the values obtained in precision variational calculations of Drake [Nucl. Instrum. Methods Phys. Res. B 5, 2207 (1988)] and Baker, Hill, and Morgan [in Relativistic, Quantum Electrodynamic and Weak Interaction Effects in Atoms, edited by Walter Johnson, Peter Mohr, and Joseph Sucher, AIP Conf. Proc. No. 189 (AIP, New York, 1989), p. 123] for both infinite and finite nuclear masses. This confirms that a discrepancy of 0.0033 cm-1 between theory and experiment is not a result of an inaccuracy of variational wave functions, but is rooted in our inadequate knowledge of the QED operators. A better understanding of the different QED contributions to the operators (such as, for example, a more precise estimate of the Bethe logarithm) is therefore needed to explain the discrepancy.

Effect of impurities on the mechanical and electronic properties of Au, Ag, and Cu monatomic chain nanowires

NASA Astrophysics Data System (ADS)

Çakır, D.; Gülseren, O.

2011-08-01

In this study, we have investigated the interaction of various different atomic and molecular species (H, C, O, H2, and O2) with the monatomic chains of Au, Ag, and Cu via total-energy calculations using the plane-wave pseudopotential method based on density functional theory. The stability, energetics, mechanical, and electronic properties of the clean and contaminated Au, Ag, and Cu nanowires have been presented. We have observed that the interaction of H, C, or O atoms with the monatomic chains are much stronger than the one of H2 or O2 molecules. The atomic impurities can easily be incorporated into these nanowires; they form stable and strong bonds with these one-dimensional structures when they are inserted in or placed close to the nanowires. Moreover, the metal-atomic impurity bond is much stronger than the metal-metal bond. Upon elongation, the nanowires contaminated with atomic impurities usually break from the remote metal-metal bond. We have observed both metallic and semiconducting contaminated nanowires depending on the type of impurity, whereas all clean monatomic chains of Au, Cu, and Ag exhibit metallic behavior. Our findings indicate that the stability and the electronic properties of these monatomic chains can be tuned by using appropriate molecular or atomic additives.

Polarizability and the optical theorem for a two-level atom with radiative broadening

NASA Astrophysics Data System (ADS)

Berman, Paul R.; Boyd, Robert W.; Milonni, Peter W.

2006-11-01

The effect of spontaneous decay on the linear polarizability of an atom is typically included by adding imaginary parts to the frequency denominators that appear in the Kramers-Heisenberg formula. It has been shown for a two-level atom with radiative broadening that these (frequency-dependent) imaginary parts must be included in both the resonant and antiresonant frequency denominators [P. W. Milonni and R. W. Boyd, Phys. Rev. A 69, 023814 (2004)]; however, the expression obtained by Milonni and Boyd for the polarizability does not satisfy the optical theorem, if contributions from non-rotating-wave terms are included. In this paper, we derive a more accurate expression for the polarizability. The calculations are rather complicated and require that we go beyond the standard Weisskopf-Wigner approximation. We present calculations carried out in both the Heisenberg and Schrödinger pictures, since they offer complementary methods for understanding the dynamics of the Rayleigh scattering associated with the atomic polarizability. Moreover, it is shown that the shifts associated with the excited state are not the Lamb shifts of an isolated atom, but depend on the dynamics of the atom-field interaction. Our results for the polarizability are consistent with those obtained recently by Loudon and Barnett using a Green’s-function approach.

Dynamical preparation of Einstein-Podolsky-Rosen entanglement in two-well Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Opanchuk, B.; He, Q. Y.; Reid, M. D.; Drummond, P. D.

2012-08-01

We propose to generate Einstein-Podolsky-Rosen (EPR) entanglement between groups of atoms in a two-well Bose-Einstein condensate using a dynamical process similar to that employed in quantum optics. A local nonlinear S-wave scattering interaction has the effect of creating spin squeezing at each well, while a tunneling coupling, analogous to a beam splitter in optics, introduces an interference between these fields that causes interwell entanglement. We consider two internal modes at each well so that the entanglement can be detected by measuring a reduction in the variances of the sums of local Schwinger spin observables. As is typical of continuous variable (CV) entanglement, the entanglement is predicted to increase with atom number. It becomes sufficiently strong at higher numbers of atoms so that the EPR paradox and steering nonlocality can be realized. The entanglement is predicted using an analytical approach and, for larger atom numbers, using stochastic simulations based on a truncated Wigner function approximation. We find generally that strong tunneling is favorable, and that entanglement persists and is even enhanced in the presence of realistic nonlinear losses.

Exact treatment of the Jaynes-Cummings model under the action of an external classical field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdalla, M. Sebawe, E-mail: m.sebaweh@physics.org; Khalil, E.M.; Mathematics Department, College of Science, Taibah University, Al-MaDinah

2011-09-15

We consider the usual Jaynes-Cummings model (JCM), in the presence of an external classical field. Under a certain canonical transformation for the Pauli operators, the system is transformed into the usual JCM. Using the equations of motion in the Heisenberg picture, exact solutions for the time-dependent dynamical operators are obtained. In order to calculate the expectation values of these operators, the wave function has been constructed. It has been shown that the classical field augments the atomic frequency {omega}{sub 0} and mixes the original atomic states. Changes of squeezing from one quadrature to another is also observed for a strongmore » value of the coupling parameter of the classical field. Furthermore, the system in this case displays partial entanglement and the state of the field losses its purity. - Highlights: > The time-dependent JCM, in the presence of the classical field, is still one of the essential problems in the quantum optics. > A new approach is applied through a certain canonical transformation. > The classical field augments the atomic frequency {omega}{sub 0} and mixes the original atomic states.« less

Localizing gravitational wave sources with single-baseline atom interferometers

NASA Astrophysics Data System (ADS)

Graham, Peter W.; Jung, Sunghoon

2018-02-01

Localizing sources on the sky is crucial for realizing the full potential of gravitational waves for astronomy, astrophysics, and cosmology. We show that the midfrequency band, roughly 0.03 to 10 Hz, has significant potential for angular localization. The angular location is measured through the changing Doppler shift as the detector orbits the Sun. This band maximizes the effect since these are the highest frequencies in which sources live for several months. Atom interferometer detectors can observe in the midfrequency band, and even with just a single baseline they can exploit this effect for sensitive angular localization. The single-baseline orbits around the Earth and the Sun, causing it to reorient and change position significantly during the lifetime of the source, and making it similar to having multiple baselines/detectors. For example, atomic detectors could predict the location of upcoming black hole or neutron star merger events with sufficient accuracy to allow optical and other electromagnetic telescopes to observe these events simultaneously. Thus, midband atomic detectors are complementary to other gravitational wave detectors and will help complete the observation of a broad range of the gravitational spectrum.

Detection of gas atoms with carbon nanotubes

PubMed Central

Arash, B.; Wang, Q.

2013-01-01

Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.

Creating high-purity angular-momentum-state Rydberg atoms by a pair of unipolar laser pulses

NASA Astrophysics Data System (ADS)

Xin, PeiPei; Cheng, Hong; Zhang, ShanShan; Wang, HanMu; Xu, ZiShan; Liu, HongPing

2018-04-01

We propose a method of producing high-purity angular-momentum-state Rydberg atoms by a pair of unipolar laser pulses. The first positive-polarity optical half-cycle pulse is used to prepare an excited-state wave packet while the second one is less intense, but with opposite polarity and time delayed, and is employed to drag back the escaping free electron and clip the shape of the bound Rydberg wave packet, selectively increasing or decreasing a fraction of the angular-momentum components. An intelligent choice of laser parameters such as phase and amplitude helps us to control the orbital-angular-momentum composition of an electron wave packet with more facility; thus, a specified angular-momentum state with high purity can be achieved. This scheme of producing high-purity angular-momentum-state Rydberg atoms has significant application in quantum-information processing.

Computational aspects of the continuum quaternionic wave functions for hydrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morais, J., E-mail: joao.pedro.morais@ua.pt

Over the past few years considerable attention has been given to the role played by the Hydrogen Continuum Wave Functions (HCWFs) in quantum theory. The HCWFs arise via the method of separation of variables for the time-independent Schrödinger equation in spherical coordinates. The HCWFs are composed of products of a radial part involving associated Laguerre polynomials multiplied by exponential factors and an angular part that is the spherical harmonics. In the present paper we introduce the continuum wave functions for hydrogen within quaternionic analysis ((R)QHCWFs), a result which is not available in the existing literature. In particular, the underlying functionsmore » are of three real variables and take on either values in the reduced and full quaternions (identified, respectively, with R{sup 3} and R{sup 4}). We prove that the (R)QHCWFs are orthonormal to one another. The representation of these functions in terms of the HCWFs are explicitly given, from which several recurrence formulae for fast computer implementations can be derived. A summary of fundamental properties and further computation of the hydrogen-like atom transforms of the (R)QHCWFs are also discussed. We address all the above and explore some basic facts of the arising quaternionic function theory. As an application, we provide the reader with plot simulations that demonstrate the effectiveness of our approach. (R)QHCWFs are new in the literature and have some consequences that are now under investigation.« less

Stabilization and Structure of wave packets in Rydberg atoms ionized by a strong light field.

PubMed

Fedorov, M; Fedorov, S

1998-09-28

New features of the phenomenon of interference stabilization of Rydberg atoms are found to exist. The main of them are: (i) dynamical stabilization, which means that in case of pulses with a smooth envelope the time-dependent residual probability for an atom to survive in bound states remains almost constant in the middle part of a pulse (at the strongest fields); (ii) existence of the strong-field stabilization of the after-pulse residual probability in case of pulses longer than the classical Kepler period; and (iii) pulsation of the time-dependent Rydberg wave packet formed in the process of photoionization.

Lineshape-asymmetry elimination in weak atomic transitions driven by an intense standing wave field

NASA Astrophysics Data System (ADS)

Antypas, Dionysios; Fabricant, Anne; Budker, Dmitry

2018-05-01

Owing to the ac-Stark effect, the lineshape of a weak optical transition in an atomic beam can become significantly distorted, when driven by an intense standing wave field. We use an Yb atomic beam to study the lineshape of the 6s2 1S0 -> 5d6s 3D1 transition, which is excited with light circulating in a Fabry-Perot resonator. We demonstrate two methods to avoid the distortion of the transition profile. Of these, one relies on the operation of the resonator in multiple longitudinal modes, and the other in multiple transverse modes.

Resonant difference-frequency atomic force ultrasonic microscope

NASA Technical Reports Server (NTRS)

Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)

2010-01-01

A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

A universal quantum frequency converter via four-wave-mixing processes

NASA Astrophysics Data System (ADS)

Cheng, Mingfei; Fang, Jinghuai

2016-06-01

We present a convenient and flexible way to realize a universal quantum frequency converter by using nondegenerate four-wave-mixing processes in the ladder-type three-level atomic system. It is shown that quantum state exchange between two fields with large frequency difference can be readily achieved, where one corresponds to the atomic resonant transition in the visible spectral region for quantum memory and the other to the telecommunication range wavelength (1550 nm) for long-distance transmission over optical fiber. This method would bring great facility in realistic quantum information processing protocols with atomic ensembles as quantum memory and low-loss optical fiber as transmission channel.

FAST TRACK COMMUNICATION: Spin waves in the (0, π) and (0, π, π) ordered SDW states of the t-t' Hubbard model: application to doped iron pnictides

NASA Astrophysics Data System (ADS)

Raghuvanshi, Nimisha; Singh, Avinash

2010-10-01

Spin waves in the (0, π) and (0, π, π) ordered spin-density-wave (SDW) states of the t-t' Hubbard model are investigated at finite doping. In the presence of small t', these composite ferro-antiferromagnetic (F-AF) states are found to be strongly stabilized at finite hole doping due to enhanced carrier-induced ferromagnetic spin couplings as in metallic ferromagnets. Anisotropic spin-wave velocities, a spin-wave energy scale of around 200 meV, reduced magnetic moment and rapid suppression of magnetic order with electron doping x (corresponding to F substitution of O atoms in LaO1 - xFxFeAs or Ni substitution of Fe atoms in BaFe2 - xNixAs2) obtained in this model are in agreement with observed magnetic properties of doped iron pnictides.

Storage and retrieval of electromagnetic waves with orbital angular momentum via plasmon-induced transparency.

PubMed

Bai, Zhengyang; Xu, Datang; Huang, Guoxiang

2017-01-23

We propose a scheme to realize the storage and retrieval of high-dimensional electromagnetic waves with orbital angular momentum (OAM) via plasmon-induced transparency (PIT) in a metamaterial, which consists of an array of meta-atoms constructed by a metallic structure loaded with two varactors. We show that due to PIT effect the system allows the existence of shape-preserving dark-mode plasmonic polaritons, which are mixture of electromagnetic-wave modes and dark oscillatory modes of the meta-atoms and may carry various OAMs. We demonstrate that the slowdown, storage and retrieval of multi-mode electromagnetic waves with OAMs can be achieved through the active manipulation of a control field. Our work raises the possibility for realizing PIT-based spatial multi-mode memory of electromagnetic waves and is promising for practical application of information processing with large capacity by using room-temperature metamaterials.

QBO of temperature in mesopause and lower thermosphere caused by solar activity variations

NASA Astrophysics Data System (ADS)

Shefov, N. N.; Semenov, A. I.

2003-04-01

On the basis of the data of the emission (hydroxyl, sodium and atomic oxygen 557.7 nm) and radiophysical (87-107 km) measurements some regularities of quasi-biennial oscillation (QBO) of the atmospheric temperature at heights of the mesopause and lower thermosphere are investigated. It is shown, that they are closely connected with quasi-biennial variations of solar activity and form within the limits of a cycle of solar activity the fading wave train of oscillations. Such behaviour of the wave train can be adequately described by the Airy function. As a result of the analysis of characteristics of QBO of solar activity during 17-23rd cycles it is shown, that to each 11-years cycle correspond its wave train of QBO. Amplitudes and periods of this wave train decrease during a cycle, i.e. it represents Not harmonious oscillation but it is a cyclic aperiodic oscillation (CAO). Therefore usual methods of Fourier analysis used earlier did not result in the same values of the period. The wave train of the current cycle begins at the end of previous and some time together with the subsequent cycle proceeds. Thus, the time sequence of activity during solar cycle represents superposition of three wave trains. Period of CAO in the beginning of a cycle has ~ 38 months and decreases to the end of a cycle up to ~ 21 months. The first wide negative minimum of Airy function describing of the wave train of CAO corresponds to solar activity minimum in the 11-year cycle. The time scale of the wave train varies from one cycle to another. Full duration of individual wave train is ~ 22 years. Owing to a mutual interference of the consecutive wave trains in the 11-year cycles the observable variations of solar activity are not identical. Structure of CAO obviously displays magnetohydrodynamic processes inside the Sun. This work was supported by the Grant No. 2274 of ISTC.

Body frame close coupling wave packet approach to gas phase atom-rigid rotor inelastic collisions

NASA Technical Reports Server (NTRS)

Sun, Y.; Judson, R. S.; Kouri, D. J.

1989-01-01

The close coupling wave packet (CCWP) method is formulated in a body-fixed representation for atom-rigid rotor inelastic scattering. For J greater than j-max (where J is the total angular momentum and j is the rotational quantum number), the computational cost of propagating the coupled channel wave packets in the body frame is shown to scale approximately as N exp 3/2, where N is the total number of channels. For large numbers of channels, this will be much more efficient than the space frame CCWP method previously developed which scales approximately as N-squared under the same conditions.

Propagating elastic vibrations dominate thermal conduction in amorphous silicon

NASA Astrophysics Data System (ADS)

Moon, Jaeyun; Latour, Benoit; Minnich, Austin J.

2018-01-01

The thermal atomic vibrations of amorphous solids can be distinguished by whether they propagate as elastic waves or do not propagate due to lack of atomic periodicity. In a -Si, prior works concluded that nonpropagating waves are the dominant contributors to heat transport, with propagating waves being restricted to frequencies less than a few THz and scattered by anharmonicity. Here, we present a lattice and molecular dynamics analysis of vibrations in a -Si that supports a qualitatively different picture in which propagating elastic waves dominate the thermal conduction and are scattered by local fluctuations of elastic modulus rather than anharmonicity. We explicitly demonstrate the propagating nature of waves up to around 10 THz, and further show that pseudoperiodic structures with homogeneous elastic properties exhibit a marked temperature dependence characteristic of anharmonic interactions. Our work suggests that most heat is carried by propagating elastic waves in a -Si and demonstrates that manipulating local elastic modulus variations is a promising route to realize amorphous materials with extreme thermal properties.

Gravitational waves from neutron stars and asteroseismology.

PubMed

Ho, Wynn C G

2018-05-28

Neutron stars are born in the supernova explosion of massive stars. Neutron stars rotate as stably as atomic clocks and possess densities exceeding that of atomic nuclei and magnetic fields millions to billions of times stronger than those created in laboratories on the Earth. The physical properties of neutron stars are determined by many areas of fundamental physics, and detection of gravitational waves can provide invaluable insights into our understanding of these areas. Here, we describe some of the physics and astrophysics of neutron stars and how traditional electromagnetic wave observations provide clues to the sorts of gravitational waves we expect from these stars. We pay particular attention to neutron star fluid oscillations, examining their impact on electromagnetic and gravitational wave observations when these stars are in a wide binary or isolated system, then during binary inspiral right before merger, and finally at times soon after merger.This article is part of a discussion meeting issue 'The promises of gravitational-wave astronomy'. © 2018 The Author(s).

Gravitational waves from neutron stars and asteroseismology

NASA Astrophysics Data System (ADS)

Ho, Wynn C. G.

2018-05-01

Neutron stars are born in the supernova explosion of massive stars. Neutron stars rotate as stably as atomic clocks and possess densities exceeding that of atomic nuclei and magnetic fields millions to billions of times stronger than those created in laboratories on the Earth. The physical properties of neutron stars are determined by many areas of fundamental physics, and detection of gravitational waves can provide invaluable insights into our understanding of these areas. Here, we describe some of the physics and astrophysics of neutron stars and how traditional electromagnetic wave observations provide clues to the sorts of gravitational waves we expect from these stars. We pay particular attention to neutron star fluid oscillations, examining their impact on electromagnetic and gravitational wave observations when these stars are in a wide binary or isolated system, then during binary inspiral right before merger, and finally at times soon after merger. This article is part of a discussion meeting issue `The promises of gravitational-wave astronomy'.

Using optical masks to create and image sub-optical wavelength atomic structures in a MOT

NASA Astrophysics Data System (ADS)

Turlapov, Andrey; Tonyushkin, Aleksey; Sleator, Tycho

2002-05-01

We have used an ``optical mask'' for Rubidium atoms in a magneto-optical trap to create and image atomic density gratings with periodicities as small as 1/8th of an optical wavelength ( ˜ 100 nm). The mask consists of a pulse of an optical standing wave (wavelength λ) resonant to an open atomic transition. The interaction pumps all atoms except those near the nodes into another hyperfine ground state, leaving a grating of ``spikes'' in atomic density in the initial ground state. The nodes of the standing wave serve as slits of the mask. By applying two such masks separated by time T, we have created atomic gratings of period λ/(2n) (or smaller) at times (n+1)/n T after the first mask pulse. For T on the order of the Talbot time (or inverse recoil frequency), quantum effects are important for the dynamics of the atomic center of mass. Under appropriate conditions, these quantum effects led to a reduction of the period of the resulting density gratings (Talbot-Lau effect). The resulting density gratings of period λ/2n (for n=1 to 4) were imaged in real time using an additional optical mask.

Strongly interacting high-partial-wave Bose gas

NASA Astrophysics Data System (ADS)

Yao, Juan; Qi, Ran; Zhang, Pengfei

2018-04-01

Motivated by recent experimental progress, we make an investigation of p - and d -wave resonant Bose gas. An explanation of the Nozières and Schmitt-Rink (NSR) scheme in terms of two-channel model is provided. Different from the s -wave case, high-partial-wave interaction supports a quasibound state in the weak-coupling regime. Within the NSR approximation, we study the equation of state, critical temperature, and particle population distributions. We clarify the effect of the quasibound state on the phase diagram and the dimer production. A multicritical point where normal phase, atomic superfluid phase, and molecular superfluid phase meet is predicted within the phase diagram. We also show the occurrence of a resonant conversion between solitary atoms and dimers when temperature kBT approximates the quasibound energy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macek, Joseph H; Sternberg, James; Ovchinnikov, Serguei Yurevich

Deep minima in He(e,2e)He{sup +} triply differential cross sections are traced to vortices in atomic wave functions. Such vortices have been predicted earlier, but the present calculations show that they have also been observed experimentally, although not recognized as vortices. Their observation in (e,2e) measurements shows that vortices play an important role in electron correlations related to the transfer of angular momentum between incident and ejected electrons. The vortices significantly extend the list of known features that summarize the general picture of electron correlations in impact ionization.

Positronium formation in e+ plus H- collisions

NASA Technical Reports Server (NTRS)

Straton, Jack C.; Drachman, Richard J.

1990-01-01

Cross sections for positronium formation by capture from the negative hydrogen ion are given. Orthogonalization corrections to the Coulomb (First) Born Approximation (CBA) differential and total cross sections are calculated using approximate H- wave functions of both Lowdin and Chandrasekhar. Various methods of orthogonalizing the unbound projectile to the possible bound states are considered. It is found that treating the atomic nuclei as if they were isotopic spin projections of a single type of nucleon gives cross sections that are an improvement over the CBA.

Volterra integral equation-factorisation method and nucleus-nucleus elastic scattering

NASA Astrophysics Data System (ADS)

Laha, U.; Majumder, M.; Bhoi, J.

2018-04-01

An approximate solution for the nuclear Hulthén plus atomic Hulthén potentials is constructed by solving the associated Volterra integral equation by series substitution method. Within the framework of supersymmetry-inspired factorisation method, this solution is exploited to construct higher partial wave interactions. The merit of our approach is examined by computing elastic scattering phases of the α {-}α system by the judicious use of phase function method. Reasonable agreements in phase shifts are obtained with standard data.

Calculating Rayleigh scattering amplitudes from 100 eV to 10 MeV. [100 eV to 10 MeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, J.C.; Reynaud, G.W.; Botto, D.J.

1979-05-01

An attempt is made to explain how to calculate the contribution to elastic photon-atom scattering due to Rayleigh scattering (the scattering off bound electrons) in the photon energy range 100 eV less than or equal to W less than or equal to 10 MeV. All intermediate calculations are described, including the calculation of the potential, bound state wave functions, matrix elements, and final cross sections. 12 references. (JFP)

Localized basis sets for unbound electrons in nanoelectronics.

PubMed

Soriano, D; Jacob, D; Palacios, J J

2008-02-21

It is shown how unbound electron wave functions can be expanded in a suitably chosen localized basis sets for any desired range of energies. In particular, we focus on the use of Gaussian basis sets, commonly used in first-principles codes. The possible usefulness of these basis sets in a first-principles description of field emission or scanning tunneling microscopy at large bias is illustrated by studying a simpler related phenomenon: The lifetime of an electron in a H atom subjected to a strong electric field.

Hyperspherical close-coupling calculations for charge-transfer cross sections in He2++H(1s) collisions at low energies

NASA Astrophysics Data System (ADS)

Liu, Chien-Nan; Le, Anh-Thu; Morishita, Toru; Esry, B. D.; Lin, C. D.

2003-05-01

A theory for ion-atom collisions at low energies based on the hyperspherical close-coupling (HSCC) method is presented. In hyperspherical coordinates the wave function is expanded in analogy to the Born-Oppenheimer approximation where the adiabatic channel functions are calculated with B-spline basis functions while the coupled hyperradial equations are solved by a combination of R-matrix propagation and the slow/smooth variable discretization method. The HSCC method is applied to calculate charge-transfer cross sections for He2++H(1s)→He+(n=2)+H+ reactions at center-of-mass energies from 10 eV to 4 keV. The results are shown to be in general good agreement with calculations based on the molecular orbital (MO) expansion method where electron translation factors (ETF’s) or switching functions have been incorporated in each MO. However, discrepancies were found at very low energies. It is shown that the HSCC method can be used to study low-energy ion-atom collisions without the need to introduce the ad hoc ETF’s, and the results are free from ambiguities associated with the traditional MO expansion approach.

Gravitational Wave Detection with Single-Laser Atom Interferometers

NASA Technical Reports Server (NTRS)

Yu, Nan; Tinto, Massimo

2011-01-01

A new design for a broadband detector of gravitational radiation relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser are used for operating the two atom interferometers. The innovation here involves the fact that the atoms in the atom interferometers are not only considered as perfect test masses, but also as highly stable clocks. Atomic coherence is intrinsically stable, and can be many orders of magnitude more stable than a laser.

Messenger Observations Inside 1 AU of Low-Frequency Magnetic Waves due to Inner Source Pickup Protons

NASA Astrophysics Data System (ADS)

Smith, C. W.; Argall, M. R.; Schwadron, N.; Joyce, C.; Isenberg, P. A.; Vasquez, B. J.; Korth, H.; Anderson, B. J.

2017-12-01

Wave excitation by pickup protons inside 1 AU have not been previously reported. Waves excited by pickup protons have a characteristic signature, a spectral peak at and above the proton gyrofrequency, that demonstrates a significant lack of particle energization beyond the initial pickup proton energy combined with pitch-angle scattering. Interstellar Hydrogen atoms cannot penetrate significantly inside about 3.5 AU due to loss of these atoms through ionization. Since the waves reported here, which are observed by the Messenger spacecraft during the cruise phase to Mercury, are not seen near the Mercury and Venus planetary encounters and there is no evidence of low-frequency waves that would indicate proximity to comets, we conclude that these waves originate from pickup protons created by the interaction of solar wind with dust relatively close to the Sun, inside 0.4 AU (Schwadron et al. 2000; Schwadron & Geiss 2000). This is the so-called inner source of pickup protons. We will present our analyses of these wave observations.Schwadron et al., J. Geophys. Res., 105, 7465, 2000.Schwadron & Geiss, J. Geophys. Res., 10, 7473, 2000.

Response of the Shockley surface state to an external electrical field: A density-functional theory study of Cu(111)

NASA Astrophysics Data System (ADS)

Berland, K.; Einstein, T. L.; Hyldgaard, P.

2012-01-01

The response of the Cu(111) Shockley surface state to an external electrical field is characterized by combining a density-functional theory calculation for a slab geometry with an analysis of the Kohn-Sham wave functions. Our analysis is facilitated by a decoupling of the Kohn-Sham states via a rotation in Hilbert space. We find that the surface state displays isotropic dispersion, quadratic until the Fermi wave vector but with a significant quartic contribution beyond. We calculate the shift in energetic position and effective mass of the surface state for an electrical field perpendicular to the Cu(111) surface; the response is linear over a broad range of field strengths. We find that charge transfer occurs beyond the outermost copper atoms and that accumulation of electrons is responsible for a quarter of the screening of the electrical field. This allows us to provide well converged determinations of the field-induced changes in the surface state for a moderate number of layers in the slab geometry.

Derivation of force field parameters for SnO2-H2O surface systems from plane-wave density functional theory calculations.

PubMed

Bandura, A V; Sofo, J O; Kubicki, J D

2006-04-27

Plane-wave density functional theory (DFT-PW) calculations were performed on bulk SnO2 (cassiterite) and the (100), (110), (001), and (101) surfaces with and without H2O present. A classical interatomic force field has been developed to describe bulk SnO2 and SnO2-H2O surface interactions. Periodic density functional theory calculations using the program VASP (Kresse et al., 1996) and molecular cluster calculations using Gaussian 03 (Frisch et al., 2003) were used to derive the parametrization of the force field. The program GULP (Gale, 1997) was used to optimize parameters to reproduce experimental and ab initio results. The experimental crystal structure and elastic constants of SnO2 are reproduced reasonably well with the force field. Furthermore, surface atom relaxations and structures of adsorbed H2O molecules agree well between the ab initio and force field predictions. H2O addition above that required to form a monolayer results in consistent structures between the DFT-PW and classical force field results as well.

Unsteady Heat-Flux Measurements of Second-Mode Instability Waves in a Hypersonic Boundary Layer

NASA Technical Reports Server (NTRS)

Kergerise, Michael A.; Rufer, Shann J.

2016-01-01

In this paper we report on the application of the atomic layer thermopile (ALTP) heat- flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are in agreement with data previously reported in the literature. Heat flux time series, and the Morlet-wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was developed to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

Unsteady heat-flux measurements of second-mode instability waves in a hypersonic flat-plate boundary layer

NASA Astrophysics Data System (ADS)

Kegerise, Michael A.; Rufer, Shann J.

2016-08-01

In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.

Theoretical aspects of studies of oxide and semiconductor surfaces using low energy positrons

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Maddox, W. B.; Weiss, A. H.

2011-01-01

This paper presents the results of a theoretical study of positron surface and bulk states and annihilation characteristics of surface trapped positrons at the oxidized Cu(100) single crystal and at both As- and Ga-rich reconstructed GaAs(100) surfaces. The variations in atomic structure and chemical composition of the topmost layers of the surfaces associated with oxidation and reconstructions and the charge redistribution at the surfaces are found to affect localization and spatial extent of the positron surface-state wave functions. The computed positron binding energy, work function, and annihilation characteristics reveal their sensitivity to charge transfer effects, atomic structure and chemical composition of the topmost layers of the surfaces. Theoretical positron annihilation probabilities with relevant core electrons computed for the oxidized Cu(100) surface and the As- and Ga-rich reconstructed GaAs(100) surfaces are compared with experimental ones estimated from the positron annihilation induced Auger peak intensities measured from these surfaces.

Photon-number statistics in resonance fluorescence

NASA Astrophysics Data System (ADS)

Lenstra, D.

1982-12-01

The theory of photon-number statistics in resonance fluorescence is treated, starting with the general formula for the emission probability of n photons during a given time interval T. The results fully confirm formerly obtained results by Cook that were based on the theory of atomic motion in a traveling wave. General expressions for the factorial moments are derived and explicit results for the mean and the variance are given. It is explicitly shown that the distribution function tends to a Gaussian when T becomes much larger than the natural lifetime of the excited atom. The speed of convergence towards the Gaussian is found to be typically slow, that is, the third normalized central moment (or the skewness) is proportional to T-12. However, numerical results illustrate that the overall features of the distribution function are already well represented by a Gaussian when T is larger than a few natural lifetimes only, at least if the intensity of the exciting field is not too small and its detuning is not too large.

Laser-modified Coulomb scattering states of an electron in the parabolic quasi-Sturmian-Floquet approach

NASA Astrophysics Data System (ADS)

Zaytsev, A. S.; Zaytsev, S. A.; Ancarani, L. U.; Kouzakov, K. A.

2018-04-01

Electron scattering states in combined Coulomb and laser fields are investigated with a nonperturbative approach based on the Hermitian Floquet theory. Taking into account the Coulomb-specific asymptotic behavior of the electron wave functions at large distances, a Lippmann-Schwinger-Floquet equation is derived in the Kramers-Henneberger frame. Such a scattering-state equation is solved numerically employing a set of parabolic quasi-Sturmian functions which have the great advantage of possessing, by construction, adequately chosen incoming or outgoing Coulomb asymptotic behaviors. Our quasi-Sturmian-Floquet approach is tested with a calculation of triple differential cross sections for a laser-assisted (e ,2 e ) process on atomic hydrogen within a first-order Born treatment of the projectile-atom interaction. Convergence with respect to the number of Floquet-Fourier expansion terms is numerically demonstrated. The illustration shows that the developed method is very efficient for the computation of light-dressed states of an electron moving in a Coulomb potential in the presence of laser radiation.

On the Highest Oxidation States of Metal Elements in MO4 Molecules (M = Fe, Ru, Os, Hs, Sm, and Pu).

PubMed

Huang, Wei; Xu, Wen-Hua; Schwarz, W H E; Li, Jun

2016-05-02

Metal tetraoxygen molecules (MO4, M = Fe, Ru, Os, Hs, Sm, Pu) of all metal atoms M with eight valence electrons are theoretically studied using density functional and correlated wave function approaches. The heavier d-block elements Ru, Os, Hs are confirmed to form stable tetraoxides of Td symmetry in (1)A1 electronic states with empty metal d(0) valence shell and closed-shell O(2-) ligands, while the 3d-, 4f-, and 5f-elements Fe, Sm, and Pu prefer partial occupation of their valence shells and peroxide or superoxide ligands at lower symmetry structures with various spin couplings. The different geometric and electronic structures and chemical bonding types of the six iso-stoichiometric species are explained in terms of atomic orbital energies and orbital radii. The variations found here contribute to our general understanding of the periodic trends of oxidation states across the periodic table.

Theoretical investigation of the structural, electronic, dynamical and thermal properties of YSn3 and YPb3

NASA Astrophysics Data System (ADS)

Kılıçarslan, Aynur; Salmankurt, Bahadır; Duman, Sıtkı

2017-02-01

We have performed an ab initio study of the structural, electronic, dynamical and thermal properties of the cubic AuCu3-type YSn3 and YPb3 by using the density functional theory, plane-wave pseudopotential method and a linear response scheme, within the generalized gradient approximation. An analysis of the electronic density of states at the Fermi level is found to be governed by the p states of Sn and Pb atoms with some contributions from the d states of Y atoms. The obtained phonon figures indicate that these material are dynamically stable in the cubic structure. Due to the metallic behavior of the compounds, the calculated zone-center phonon modes are triply degenerate. Also the thermal properties have been examined.

Asymptotic form of the charge exchange cross section in the three body rearrangement collisions

NASA Technical Reports Server (NTRS)

Omidvar, K.

1975-01-01

A three body general rearrangement collision is considered where the initial and final bound states are described by the hydrogen-like wave functions. Mathematical models are developed to establish the relationships of quantum number, the reduced mass, and the nuclear charge of the final state. It is shown that for the low lying levels, the reciprocal of n cubed scaling law at all incident energies is only approximately satisfied. The case of the symmetric collisions is considered and it is shown that for high n and high incident energy, E, the cross section behaves as the reciprocal of E cubed. Zeros and minima in the differential cross sections in the limit of high n for protons on atomic hydrogen and positrons on atomic hydrogen are given.

Atomic Processes and Diagnostics of Low Pressure Krypton Plasma

NASA Astrophysics Data System (ADS)

Srivastava, Rajesh; Goyal, Dipti; Gangwar, Reetesh; Stafford, Luc

2015-03-01

Optical emission spectroscopy along with suitable collisional-radiative (CR) model is used in plasma diagnostics. Importance of reliable cross-sections for various atomic processes is shown for low pressure argon plasma. In the present work, radially-averaged Kr emission lines from the 2pi --> 1sj were recorded as a function of pressure from 1 to 50mTorr. We have developed a CR model using our fine-structure relativistic-distorted wave cross sections. The various processes considered are electron-impact excitation, ionization and their reverse processes. The required rate coefficients have been calculated from these cross-sections assuming Maxwellian energy distribution. Electron temperature obtained from the CR model is found to be in good agreement with the probe measurements. Work is supported by IAEA Vienna, DAE-BRNS Mumbai and CSIR, New Delhi.

Observation of three-photon bound states in a quantum nonlinear medium

NASA Astrophysics Data System (ADS)

Liang, Qi-Yu; Venkatramani, Aditya V.; Cantu, Sergio H.; Nicholson, Travis L.; Gullans, Michael J.; Gorshkov, Alexey V.; Thompson, Jeff D.; Chin, Cheng; Lukin, Mikhail D.; Vuletić, Vladan

2018-02-01

Bound states of massive particles, such as nuclei, atoms, or molecules, constitute the bulk of the visible world around us. By contrast, photons typically only interact weakly. We report the observation of traveling three-photon bound states in a quantum nonlinear medium where the interactions between photons are mediated by atomic Rydberg states. Photon correlation and conditional phase measurements reveal the distinct bunching and phase features associated with three-photon and two-photon bound states. Such photonic trimers and dimers possess shape-preserving wave functions that depend on the constituent photon number. The observed bunching and strongly nonlinear optical phase are described by an effective field theory of Rydberg-induced photon-photon interactions. These observations demonstrate the ability to realize and control strongly interacting quantum many-body states of light.

Bridging the gap between atomic microstructure and electronic properties of alloys: The case of (In,Ga)N

NASA Astrophysics Data System (ADS)

Chan, J. A.; Liu, J. Z.; Zunger, Alex

2010-07-01

The atomic microstructure of alloys is rarely perfectly random, instead exhibiting differently shaped precipitates, clusters, zigzag chains, etc. While it is expected that such microstructural features will affect the electronic structures (carrier localization and band gaps), theoretical studies have, until now, been restricted to investigate either perfectly random or artificial “guessed” microstructural features. In this paper, we simulate the alloy microstructures in thermodynamic equilibrium using the static Monte Carlo method and study their electronic structures explicitly using a pseudopotential supercell approach. In this way, we can bridge atomic microstructures with their electronic properties. We derive the atomic microstructures of InGaN using (i) density-functional theory total energies of ˜50 ordered structures to construct a (ii) multibody cluster expansion, including strain effects to which we have applied (iii) static Monte Carlo simulations of systems consisting of over 27000 atoms to determine the equilibrium atomic microstructures. We study two types of alloy thermodynamic behavior: (a) under lattice incoherent conditions, the formation enthalpies are positive and thus the alloy system phase-separates below the miscibility-gap temperature TMG , (b) under lattice coherent conditions, the formation enthalpies can be negative and thus the alloy system exhibits ordering tendency. The microstructure is analyzed in terms of structural motifs (e.g., zigzag chains and InnGa4-nN tetrahedral clusters). The corresponding electronic structure, calculated with the empirical pseudopotentials method, is analyzed in terms of band-edge energies and wave-function localization. We find that the disordered alloys have no electronic localization but significant hole localization, while below the miscibility gap under the incoherent conditions, In-rich precipitates lead to strong electron and hole localization and a reduction in the band gap.

Combined Molecular and Spin Dynamics Simulation of Lattice Vacancies in BCC Iron

NASA Astrophysics Data System (ADS)

Mudrick, Mark; Perera, Dilina; Eisenbach, Markus; Landau, David P.

Using an atomistic model that treats translational and spin degrees of freedom equally, combined molecular and spin dynamics simulations have been performed to study dynamic properties of BCC iron at varying levels of defect impurity. Atomic interactions are described by an empirical many-body potential, and spin interactions with a Heisenberg-like Hamiltonian with a coordinate dependent exchange interaction. Equations of motion are solved numerically using the second-order Suzuki-Trotter decomposition for the time evolution operator. We analyze the spatial and temporal correlation functions for atomic displacements and magnetic order to obtain the effect of vacancy defects on the phonon and magnon excitations. We show that vacancy clusters in the material cause splitting of the characteristic transverse spin-wave excitations, indicating the production of additional excitation modes. Additionally, we investigate the coupling of the atomic and magnetic modes. These modes become more distinct with increasing vacancy cluster size. This material is based upon work supported by the U.S. Department of Energy Office of Science Graduate Student Research (SCGSR) program.

Probing density and spin correlations in two-dimensional Hubbard model with ultracold fermions

NASA Astrophysics Data System (ADS)

Chan, Chun Fai; Drewes, Jan Henning; Gall, Marcell; Wurz, Nicola; Cocchi, Eugenio; Miller, Luke; Pertot, Daniel; Brennecke, Ferdinand; Koehl, Michael

2017-04-01

Quantum gases of interacting fermionic atoms in optical lattices is a promising candidate to study strongly correlated quantum phases of the Hubbard model such as the Mott-insulator, spin-ordered phases, or in particular d-wave superconductivity. We experimentally realise the two-dimensional Hubbard model by loading a quantum degenerate Fermi gas of 40 K atoms into a three-dimensional optical lattice geometry. High-resolution absorption imaging in combination with radiofrequency spectroscopy is applied to spatially resolve the atomic distribution in a single 2D layer. We investigate in local measurements of spatial correlations in both the density and spin sector as a function of filling, temperature and interaction strength. In the density sector, we compare the local density fluctuations and the global thermodynamic quantities, and in the spin sector, we observe the onset of non-local spin correlation, signalling the emergence of the anti-ferromagnetic phase. We would report our recent experimental endeavours to investigate further down in temperature in the spin sector.

Barium-strontium-titanate etching characteristics in chlorinated discharges

NASA Astrophysics Data System (ADS)

Stafford, Luc; Margot, Joëlle; Langlois, Olivier; Chaker, Mohamed

2003-07-01

The etching characteristics of barium-strontium-titanate (BST) were investigated using a high-density plasma sustained by surface waves at 190 MHz in Ar/Cl2 gas mixtures. The etch rate was examined as a function of both the total gas pressure and the Cl2 fraction in Ar/Cl2 using a wafer temperature of 10 °C. The results were correlated to positive ion density and plasma composition obtained from Langmuir probes and mass spectrometry. The BST etch rate was found to increase linearly with the positive ion density and to decrease with increasing chlorine atom concentration. This result indicates that for the temperature conditions used, the interaction between chlorine and BST yields compounds having a volatility that is lower than the original material. As a consequence, the contribution of neutral atomic Cl atoms to the etch mechanism is detrimental, thereby reducing the etch rate. As the wafer temperature increases, the role of chemistry in the etching process is enhanced.

Eigenstates and dynamics of Hooke's atom: Exact results and path integral simulations

NASA Astrophysics Data System (ADS)

Gholizadehkalkhoran, Hossein; Ruokosenmäki, Ilkka; Rantala, Tapio T.

2018-05-01

The system of two interacting electrons in one-dimensional harmonic potential or Hooke's atom is considered, again. On one hand, it appears as a model for quantum dots in a strong confinement regime, and on the other hand, it provides us with a hard test bench for new methods with the "space splitting" arising from the one-dimensional Coulomb potential. Here, we complete the numerous previous studies of the ground state of Hooke's atom by including the excited states and dynamics, not considered earlier. With the perturbation theory, we reach essentially exact eigenstate energies and wave functions for the strong confinement regime as novel results. We also consider external perturbation induced quantum dynamics in a simple separable case. Finally, we test our novel numerical approach based on real-time path integrals (RTPIs) in reproducing the above. The RTPI turns out to be a straightforward approach with exact account of electronic correlations for solving the eigenstates and dynamics without the conventional restrictions of electronic structure methods.

MCDF calculations of Auger cascade processes

NASA Astrophysics Data System (ADS)

Beerwerth, Randolf; Fritzsche, Stephan

2017-10-01

We model the multiple ionization of near-neutral core-excited atoms where a cascade of Auger processes leads to the emission of several electrons. We utilize the multiconfiguration Dirac-Fock (MCDF) method to generate approximate wave functions for all fine-structure levels and to account for all decays between them. This approach allows to compute electron spectra, the population of final-states and ion yields, that are accessible in many experiments. Furthermore, our approach is based on the configuration interaction method. A careful treatment of correlation between electronic configurations enables one to model three-electron processes such as an Auger decay that is accompanied by an additional shake-up transition. Here, this model is applied to the triple ionization of atomic cadmium, where we show that the decay of inner-shell 4p holes to triply-charged final states is purely due to the shake-up transition of valence 5s electrons. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

A Comparison of Laser Induced Florescence and Continuous Wave Ring Down Spectroscopy Measurements of Argon Ion and Neutral VDFs in a Helicon Plasma

NASA Astrophysics Data System (ADS)

McCarren, Dustin; Vandervort, Robert; Carr, Jerry, Jr.; Scime, Earl

2012-10-01

In this work, we compare two spectroscopic methods for measuring the velocity distribution functions (VDFs) of argon ions and neutrals in a helicon plasma: laser induced florescence (LIF) and continuous wave cavity ring down spectroscopy (CW-CRDS). An established and powerful technique, LIF suffers from the requirement that the initial state of the LIF sequence have a substantial density. In most cases, this requirement limits LIF to ions and atoms with large metastable state densities for the given plasma conditions. CW-CRDS is considerably more sensitive than LIF and can potentially be applied to much lower density populations of ion and atom states. However, CRDS is a line integrated technique that lacks the spatial resolution of LIF. CRDS is a proven, ultra-sensitive, cavity enhanced absorption spectroscopy technique and when combined with a CW diode laser that has a sufficiently narrow linewidth, the Doppler broadened absorption line, i.e., the VDFs, can be measured. We present CW-CRDS and LIF measurements of the VDFs in an argon plasma using the 668.614 nm (in vacuum) line of Ar II and the 667.9125 nm (in vacuum) line of Ar I.

Generalized Jastrow Variational Method for Liquid HELIUM-3-HELIUM-4 Mixtures at T = 0 K.

NASA Astrophysics Data System (ADS)

Mirabbaszadeh, Kavoos

Microscopic theory of dilute liquid { ^3 He}-{^4 He} mixtures is of great interest, because it provides a physical realization of a nearly degenerate weakly interacting Fermion system. An understanding of properties of the mixtures has received considerable attention both theoretically and experimentally over the past thirty years. We present here a variational procedure based on the Jastrow function for the ground state of {^3 He}- {^4 He} mixtures by minimizing the total energy of the mixture using the hypernetted-chain (HNC) approximation and the Percus-Yevick (PY) approximation for the two body correlation functions. Our goal is to compute from first principles the internal energy of the system and the various two body correlation functions at various densities and compare the results with experiment. The Jastrow variational method for the ground state energy of liquid {^4 He} consists of the following ansatz for the wave function Psi_alpha {rm(vec r_{1 alpha},} {vec r_{2alpha},} dots, {vec r_{N _alpha})} = prod _{rm i < j} {rm f_ {alphaalpha}(r_{ij}). } For a {^3 He } system the corresponding ansatz is Psi_beta {rm( vec r_{1beta},} {vec r_{2beta },} dots, {vec r_{N_beta})} = {[prod _{i < j} f_{betabeta }(r_{ij})]} Phi {rm( vec r_{1beta},} {vec r_{2beta },} dots, {vec r_{Nbeta}),} where Phi is a Slater determinant of plane waves for the ground state of the Fermion system. The total energy per particle can be written in the form: E = x_sp{alpha}{2} E_{alphaalpha} + x_sp{beta}{2 }E_{betabeta } + 2x_{alpha} x_{beta}E _{alphabeta}, where E_{alphaalpha} , E_{betabeta} , E_{alphabeta} are unknown parameters to be determined from a microscopic theory. Using the Jastrow wave function Psi for the mixture, a general expression is given for the ground state energy in terms of the two body potential and two and three body correlation functions. The Kirkwood Super-position Approximation (KSA) is used for the three-body correlation functions. The antisymmetry of the wave function for Fermions is incorporated following the procedure given earlier by Lado, Inguva and Smith. This procedure for treating the antisymmetry of the wave function simplifies the equations for the two-body correlation functions considerably. The equations for the correlation functions are solved in the hypernetted-chain approximation. Once the two-particle correlation functions for the mixture ( ^3He-^4He) have been obtained, the energy is minimized with respect to the variational parameters involved in the Jastrow wave function. The binding energy and the optimal correlation functions are then obtained as a function of the concentration of ^3He atoms in the mixture. (Abstract shortened with permission of author.).

A square-wave wavelength modulation system for automatic background correction in carbon furnace atomic emission spectrometry

NASA Astrophysics Data System (ADS)

Bezur, L.; Marshall, J.; Ottaway, J. M.

A square-wave wavelength modulation system, based on a rotating quartz chopper with four quadrants of different thicknesses, has been developed and evaluated as a method for automatic background correction in carbon furnace atomic emission spectrometry. Accurate background correction is achieved for the residual black body radiation (Rayleigh scatter) from the tube wall and Mie scatter from particles generated by a sample matrix and formed by condensation of atoms in the optical path. Intensity modulation caused by overlap at the edges of the quartz plates and by the divergence of the optical beam at the position of the modulation chopper has been investigated and is likely to be small.

Elastic scattering losses from colliding Bose-Einstein condensates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zin Pawel; Chwedenczuk, Jan; Trippenbach, Marek

2006-03-15

Bragg diffraction divides a Bose-Einstein condensate into two overlapping components, moving with respect to each other with high momentum. Elastic collisions between atoms from distinct wave packets can significantly deplete the condensate. Recently, Zin et al. [Phys. Rev. Lett. 94, 200401 (2005)] introduced a model of two counterpropagating atomic Gaussian wave packets incorporating the dynamics of the incoherent scattering processes. Here we study the properties of this model in detail, including the nature of the transition from spontaneous to stimulated scattering. Within the first-order approximation, we derive analytical expressions for the density matrix and anomalous density that provide excellent insightmore » into correlation properties of scattered atoms.« less