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Results for “COULOMB POTENTIAL”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Positron scattering from hydrogen atom with screened Coulomb potentials

Elastic positron-hydrogen collisions with screened Coulomb potentials have been investigated using a second-order distorted wave Born approximation in the momentum space. Two types of potentials have been considered, namely, static screened Coulomb potential and exponential cosine-screened Coulomb potential. Using a simple variationally determined hydrogenic wave function it has been possible to obtain the scattering amplitude in a closed form. A detailed study has been made on the differential and total cross sections in the energy range 20–300 eV.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

On a relativistic particle and a relativistic position-dependent mass particle subject to the Klein–Gordon oscillator and the Coulomb potential

The relativistic quantum dynamics of an electrically charged particle subject to the Klein–Gordon oscillator and the Coulomb potential is investigated. By searching for relativistic bound states, a particular quantum effect can be observed: a dependence of the angular frequency of the Klein–Gordon oscillator on the quantum numbers of the system. The meaning of this behaviour of the angular frequency is that only some specific values of the angular frequency of the Klein–Gordon oscillator are permitted in order to obtain bound state solutions. As an example, we obtain both the angular frequency and the energy level associated with the ground state of the relativistic system. Further, we analyse the behaviour of a relativistic position-dependent mass particle subject to the Klein–Gordon oscillator and the Coulomb potential.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Unraveling nonadiabatic ionization and Coulomb potential effect in strong-field photoelectron holography

Strong field photoelectron holography has been proposed as a means for interrogating the spatial and temporal information of electrons and ions in a dynamic system. After ionization, part of the electron wave packet may directly go to the detector (the reference wave), while another part may be driven back and scatters off the ion(the signal wave). The interference hologram of the two waves may be used to extract target information embedded in the collision process . Unlike conventional optical holography, however, propagation of the electron wave packet is affected by the Coulomb potential as well as by the laser field. In addition, electrons are emitted over the whole laser pulse duration, thus multiple interferences may occur. In this work, we used a generalized quantum-trajectory Monte Carlo method to investigate the effect of Coulomb potential and the nonadiabatic subcycle ionization on the photoelectron hologram. Here, we showed that photoelectron hologram can be well described only when the effect of nonadiabatic ionization is accounted for, and Coulomb potential can be neglected only in the tunnel ionization regime. Our results help paving the way for establishing photoelectron holography for probing spatial and dynamic properties of atoms and molecules.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Magnetic dipolar and quadrupolar transitions in two-electron atoms under exponential-cosine-screened Coulomb potential

A detailed investigation of the magnetic dipolar and quadrupolar excitation energies and transition probabilities of helium isoelectronic He, Be{sup 2+}, C{sup 4+}, and O{sup 6+} have been performed under exponential cosine screened Coulomb potential generated in a plasma environment. The low-lying excited states 1s{sup 2}:{sup 1}S{sup e} → 1sns:{sup 3}S{sup e}{sub 0}, and 1snp:{sup 3}P{sup o}{sub 2} (n = 2, 3, 4, and 5) are considered. The variational time-dependent coupled Hartree-Fock scheme has been used. The effect of the confinement produced by the potential on the structural properties is investigated for increasing coupling strength of the plasma. It is noted that there is a gradual destabilization of the energy of the system with the reduction of the ionization potential and the number of excited states. The effect of the screening enhancement on the excitation energies and transition probabilities has also been investigated and the results compared with those available for the free systems and under the simple screened Coulomb potential.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

On the Trotter Error in Many-body Quantum Dynamics with Coulomb Potentials

Efficient simulation of many-body quantum systems is central to advances in physics, chemistry, and quantum computing, with a key question being whether the simulation cost scales polynomially with the system size. Here, in this work, we analyze many-body quantum systems with Coulomb interactions, which are fundamental to electronic and molecular systems. We prove that Trotterization for such unbounded Hamiltonians achieves a 1/4-order convergence rate, with explicit polynomial dependence on the number of particles. The result holds for all initial wavefunctions in the domain of the Hamiltonian, and the 1/4-order convergence rate is optimal, as previous work has numerically demonstrated that it can be saturated by a specific initial ground state. The main challenges arise from the many-body structure and the singular nature of the Coulomb potential. Our proof strategy differs from prior state-of-the-art Trotter analyses, addressing both difficulties in a unified framework. Our analysis treats the Coulomb potential as an unbounded operator without modification or regularization, and does not rely on spatial discretization, making it compatible with both first- and second-quantized circuit constructions.

Fang, Di [Duke Univ., Durham, NC (United States)]↗
DOE OSTI2013

Stationary solution of NLFP with coulombic potential

In a previous paper, Grassi (2012) [39], a new entropy form has been proposed for which it is possible to obtain a stationary solution of the Non-Linear Fokker-Planck equation (referred as NLFP) with coulombic-like potentials. In this paper we analyze the stationary solution of NLFP obtained by using pure coulombic potentials and we will use this solution to study an 'atomic-like' system. - Highlights: Black-Right-Pointing-Pointer The entropy introduced in a previous work has been studied for a coulombic potential. Black-Right-Pointing-Pointer From this entropy form a NLFP has been derived for a pure coulombic potential. Black-Right-Pointing-Pointer The stationary solution of the NLFP for an 'atomic-like' system has been obtained. Black-Right-Pointing-Pointer A comparison with Boltzmann entropy has been proposed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

The Connection between Resonances and Bound States in the Presence of a Coulomb Potential

The connection between resonant metastable states and bound states with changing potential strength in the presence of a Coulomb potential is fundamentally different from the case of short-range potentials. This phenomenon is central to the physics of dissociative recombination of electrons with molecular cations. In this paper, it is verified computationally that there is no direct connection between the resonance pole of the S-matrix and any pole in the bound state spectrum. A detailed analysis is presented of the analytic structure of the scattering matrix, in which the resonance pole remains distinct in the complex k-plane while a new state appears in the bound state spectrum. A formulation of quantum-defect theory is developed based on the scattering matrix, which nonetheless exposes a close analytic relation between the resonant and bound state poles and thereby reveals the connection between quantum-defect theory and analytic S-matrix theory in the complex energy and momentum planes. One-channel and multichannel versions of the expressions with numerical examples for simple models are given, and the formalism is applied to give a unified picture of ab initio electronic structure and scattering calculations for e-O 2 + and e-H 2 + scattering.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Solution of D dimensional Dirac equation for coulombic potential using NU method and its thermodynamics properties

The analytical solution of Ddimensional Dirac equation for Coulombic potential is investigated using Nikiforov-Uvarov method. The D dimensional relativistic energy spectra are obtained from relativistic energy eigenvalue equation by using Mat Lab software.The corresponding D dimensional radial wave functions are formulated in the form of generalized Jacobi and Laguerre Polynomials. In the non-relativistic limit, the relativistic energy equation reduces to the non-relativistic energy which will be applied to determine some thermodynamical properties of the system. The thermodynamical properties of the system are expressed in terms of error function and imaginary error function.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Dynamics of atoms in strong laser fields I: A quasi analytical model in momentum space based on a Sturmian expansion of the interacting nonlocal Coulomb potential

In this study we present a model that we have formulated in the momentum space to describe atoms interacting with intense laser fields. As a further step, it follows our recent theoretical approach in which the kernel of the reciprocal-space time-dependent Schrödinger equation (TDSE) is replaced by a finite sum of separable potentials, each of them supporting one bound state of atomic hydrogen (Tetchou Nganso et al. 2013). The key point of the model is that the nonlocal interacting Coulomb potential is expanded in a Coulomb Sturmian basis set derived itself from a Sturmian representation of Bessel functions of the first kind in the position space. As a result, this decomposition allows a simple spectral treatment of the TDSE in the momentum space. In order to illustrate the credibility of the model, we have considered the test case of atomic hydrogen driven by a linearly polarized laser pulse, and have evaluated analytically matrix elements of the atomic Hamiltonian and dipole coupling interaction. For various regimes of the laser parameters used in computations our results are in very good agreement with data obtained from other time-dependent calculations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

A comparative study of two-electron systems with screened Coulomb potentials

Highlights: • A comparison criterion for screened potentials is conjectured for two-electron atoms. • The limits of validity of the correlation hypothesis are discussed. • Independent Hylleraas and Lagrange mesh calculations verify the comparison criterion. - Abstract: The relative ordering of energy levels is investigated for bound two-electron systems with potentials of the form V(r{sub 1},r{sub 2},r{sub 12})=Z(v(r{sub 1})+v(r{sub 2}))-v(r{sub 12}). Given the two one-body binding potentials v{sup (1)}(r) and v{sup (2)}(r), it is argued that if f(r)≡v{sup (1)}(r)-v{sup (2)}(r) is positive and monotonically decreasing upon increasing r then the corresponding eigenvalues of the two-electron Hamiltonians H{sub i}=-(1/2)(∇{sub 1}{sup 2}+∇{sub 2}{sup 2})+Z(v{sup (i)}(r{sub 1})+v{sup (i)}(r{sub 2}))-v{sup (i)}(r{sub 12}) , i=1,2are highly likely to be pairwise ordered, i.e., E{sub n}{sup (1)}≥E{sub n}{sup (2)}, n=1,2,…, where E{sub 1}{sup (i)}≤E{sub 2}{sup (i)}≤⋯≤E{sub k}{sup (i)}≤⋯ , for both i=1 and i=2. This conjecture certainly holds at sufficiently large Z. The range of n may be finite or infinite, depending on the nature of the potentials. In fact, the range of values of n for v{sup (1)}(r) may be shorter than that of v{sup (2)}(r) (which is more binding). The one-electron potentials specifically considered are: v(r)={ v_C(r) =-(1/r) Coulomb v_D(r) =-(1/r)exp(-λr) Debye (Yukawa) v_H_u(r) =-(λ/(exp(λr)-1)) Hulthén v_E_C_S_C(r) =-(1/r)exp(-λr)cos(λr) ECSC}{sup ∗} , ){sup ∗}Exponential-Cosine-Screened-Coulomb where λ is the screening parameter. For each of the λ-dependent potentials we compare one- and two-electron spectra corresponding to distinct values of λ. This is followed by pairwise comparison of distinct potentials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Quantum Drude oscillators coupled with Coulomb potential as an efficient model for bonded and non-covalent interactions in atomic dimers

The quantum Drude oscillator (QDO) model has been widely used as an efficient surrogate to describe the electric response properties of matter as well as long-range interactions in molecules and materials. Most commonly, QDOs are coupled within the dipole approximation so that the Hamiltonian can be exactly diagonalized, which forms the basis for the many-body dispersion method [Phys. Rev. Lett. 108, 236402 (2012)]. The dipole coupling is efficient and allows us to study non-covalent many-body effects in systems with thousands of atoms. However, there are two limitations: (i) the need to regularize the interaction at short distances with empirical damping functions and (ii) the lack of multipolar effects in the coupling potential. In this work, we convincingly address both limitations of the dipole-coupled QDO model by presenting a numerically exact solution of the Coulomb-coupled QDO model by means of quantum Monte Carlo methods. We calculate the potential-energy surfaces of homogeneous QDO dimers, analyzing their properties as a function of the three tunable parameters: frequency, reduced mass, and charge. We study the coupled-QDO model behavior at short distances and show how to parameterize this model to enable an effective description of chemical bonds, such as the covalent bond in the H2 molecule.

Chemistry↗
DOE OSTI2016

Analytical solutions of the Dirac equation under Hellmann–Frost–Musulin potential

The approximate analytical solutions of the Dirac equation with Hellmann–Frost–Musulin potential have been studied by using the generalized parametric Nikiforov–Uvarov (NU) method for arbitrary spin–orbit quantum number k under the spin and pseudospin symmetries. The Hellmann–Frost–Musulin potential is a superposition potential that consists of Yukawa potential, Coulomb potential, and Frost–Musulin potential. As a particular case, we found the energy levels of the non-relativistic limit of the spin symmetry. The energy equation of Yukawa potential, Coulomb potential, Hellmann potential and Frost–Musulin potential are obtained. Energy values are generated for some diatomic molecules.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗