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Lee M. Thompson - One of the best experts on this subject based on the ideXlab platform.
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Global elucidation of broken symmetry solutions to the Independent Particle Model through a Lie algebraic approach.
The Journal of chemical physics, 2018Co-Authors: Lee M. ThompsonAbstract:Broken symmetry solutions—solutions to the Independent Particle Model that do not obey all symmetries required by the Hamiltonian—have attracted significant interest for capturing multireference properties with mean-field scaling. However, identification and optimization of broken-symmetry solutions is difficult owing to the non-linear nature of the self-consistent field (SCF) equations, particularly for solutions belonging to low-symmetry subgroups and where multiple broken symmetry solutions are sought. Linearization of SCF solution space results in the Lie algebra, which this work utilizes as a framework for elucidation of the set of solutions that exist at the desired symmetry. To demonstrate that searches constructed in the Lie algebra yield the set of broken symmetry solutions, a grid-based search of real-restricted, real-unrestricted, complex-restricted, paired-unrestricted, and real-general solutions of the C2v (nearly D4h) H4 molecule is performed.Broken symmetry solutions—solutions to the Independent Particle Model that do not obey all symmetries required by the Hamiltonian—have attracted significant interest for capturing multireference properties with mean-field scaling. However, identification and optimization of broken-symmetry solutions is difficult owing to the non-linear nature of the self-consistent field (SCF) equations, particularly for solutions belonging to low-symmetry subgroups and where multiple broken symmetry solutions are sought. Linearization of SCF solution space results in the Lie algebra, which this work utilizes as a framework for elucidation of the set of solutions that exist at the desired symmetry. To demonstrate that searches constructed in the Lie algebra yield the set of broken symmetry solutions, a grid-based search of real-restricted, real-unrestricted, complex-restricted, paired-unrestricted, and real-general solutions of the C2v (nearly D4h) H4 molecule is performed.
W. G. Lynch - One of the best experts on this subject based on the ideXlab platform.
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Survey of ground state neutron spectroscopic factors from Li to Cr isotopes.
Physical review letters, 2005Co-Authors: M. B. Tsang, Jenny Lee, W. G. LynchAbstract:Present and planned rare isotope accelerators offer opportunities to explore the structure of unstable nuclei. Like their stable counterparts, the structure of these nuclei reflects interplay between single-Particle degrees of freedom that govern the shell structure of nuclei [1] and collective degrees of freedom that govern nuclear deformations [2]. Single-Particle properties, such as the shell closure at ‘‘magic’’ neutron or proton numbers, can be approximated by the Independent Particle Model, which assumes that nucleons move in a mean-field potential [1]. Residual nucleon-nucleon interactions, however, mix the singleParticle states of the Independent Particle Model [3‐5]. Understanding this mixing is an important objective of modern structure calculations; it alters the occupancies, or spectroscopic factors (SF), of single-nucleon orbits from their Independent Particle Model values, and it can even modify the magic numbers of nuclei that have a large neutron excess or are near the proton drip line [6]. Experimental measurements of the SF’s for singlenucleon orbits within the quantum states of nuclei provide the key experimental probe of single-Particle dynamics. Both transfer and knockout reactions have been widely studied in order to determine the SF’s of single-nucleon orbits. Transfer reactions comprise the preponderance of such studies in the past four decades. However, their extracted SF’s often varied widely, reflecting inconsistencies in the choice of optical potentials for the incoming and outgoing channels to which the transfer cross sections are sensitive [7,8]. In this Letter, we reanalyze most of the
Marko Horbatsch - One of the best experts on this subject based on the ideXlab platform.
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Mean-field description of B2+- Ne collisions with active target and projectile electrons
Journal of Physics: Conference Series, 2014Co-Authors: Gerald Schenk, Tom Kirchner, Marko HorbatschAbstract:The B2+- Ne collision system is studied in an Independent Particle Model that takes both projectile and target electrons into account. It is shown that the projectile electrons play an active role in processes, in which the projectile charge state does not change.
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A reduced-geometry Independent Particle Model calculation of high harmonic generation from closed-shell diatomic molecules
Canadian Journal of Physics, 2012Co-Authors: Mitsuko Murakami, Tom Kirchner, Marko HorbatschAbstract:We propose a simple Model to calculate high harmonic spectra from closed-shell diatomic molecules based on the time-dependent Schrodinger equation. Quasi-Coulomb potentials are used to represent the two-center geometry of a diatomic molecule in two dimensions. A few outer occupied molecular orbitals are evolved Independently using a single- electron Hamiltonian, and the harmonic spectra are evaluated from a coherent sum of single-electron dipole accelerations. According to this Independent Particle Model, harmonic spectra from individual orbitals follow the semiclassical cutoff law, but their relative strengths vary depending on molecular orientations. When the contributions from different orbitals are of comparable strength, their net spectrum extends to the inner-orbital cutoffs, and in some cases acquires a local minimum where harmonic spectra from different molecular orbitals interfere destructively because of their phase difference. PACS Nos: 33.20.Xx, 32.80.Rm, 42.65.Ky Resume : Nous proposons un Modele simple pour calculer, a partir de l'equation de Schrodinger dependante du temps, les spectres hautement harmoniques de molecules diatomiques a couches fermees. Nous utilisons des potentiels quasi-coulombiens pour representer la geometrie a deux centres d'une molecule diatomique en deux dimensions. Un Hamiltonien a un electron permet d'evaluer l'evolution independante de quelques orbitales exterieures occupees et nous calculons les spectres harmoniques a partir d'une somme coherente d'accelerations dipolaires de simples electrons. Selon ce Modele a electrons independants, les spectres harmoniques a partir d'orbitales a une particule suivent la loi de coupure semi- classique, mais leurs forces relatives varient suivant les orientations moleculaires. Lorsque les contributions de differentes orbitales sont de force comparable, leur spectre net s'etend aux coupures des orbitales interieures et, dans certains cas, acquiere un minimum local la ou les spectres harmoniques de differentes orbitales moleculaires interferent de facon des- tructive a cause de leur difference de phase. (Traduit par la Redaction)
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Time-dependent Independent-Particle Model calculation of multiple capture and ionization processes in p-Ar, (p)over-bar- Ar, and He2+-Ar collisions
Physical Review A, 2002Co-Authors: Tom Kirchner, Marko Horbatsch, H. J. LuddeAbstract:Previous work on multielectron transitions in proton, antiproton, and He{sup 2+}-ion impact on neon is extended to the case of argon targets for collision energies in the 5-1000 keV/amu range. Global quantities such as net electron loss from the target, net capture, and net ionization are predicted within experimental errors using a spherically symmetric optimized effective target atom potential with dynamical screening effects based on the time-dependent net ionization probability. The inclusion of target response is crucial in order to obtain correct positions and heights for the peaks in the net ionization cross sections. Effects due to cascading following multiple outer-shell excitation are found to be appreciable at energies between 10 and 100 keV/amu, but are overestimated by the statistical Model. L-shell vacancy production is reported to affect recoil charge state production at energies above 200 keV/amu for charge states q{>=}3. At low and intermediate energies, the Independent-Particle Model is shown to overestimate q-fold recoil ion production significantly for q{>=}3 for proton impact signaling the role of electronic correlations for these channels. For antiproton impact the q=3 cross section is consistent with the Independent-Particle Model.
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Independent Particle Model description of multiple ionization dynamics in fast ion-atom collisions
Journal of Physics B: Atomic Molecular and Optical Physics, 1992Co-Authors: Marko HorbatschAbstract:The time-dependent dynamics of the many-electron density and its interaction with projectile and target nuclei is described within the semiclassical (=0) Vlasov Model. Differential cross sections for multiple ionization as a function of projectile scattering angle and transverse target recoil momentum are calculated. Average scattering angles are obtained as a function of impact parameter within the Model taking into account a given number of ejected electrons for each recoil ion charge state. Other results include projectile energy loss and the relationship between projectile and target nucleon motion. Comparison with experiment and classical N-Particle simulations (N-CTMC) is made for two systems, namely, C6+-Ne and U3+-Ne at collision energies of 0.8 and 1.4 MeV amu-1 respectively.
Eduardo R. Mucciolo - One of the best experts on this subject based on the ideXlab platform.
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Coulomb-blockade conductance-peak-height fluctuations in quantum dots and the Independent-Particle Model
Physical Review B, 1999Co-Authors: Raúl O. Vallejos, Caio H. Lewenkopf, Eduardo R. MuccioloAbstract:We study the combined effect of finite temperature, underlying classical dynamics, and deformations on the statistical properties of Coulomb blockade conductance peaks in quantum dots. These effects are considered in the context of the single-Particle plus constant-interaction theory of the Coulomb blockade. We present numerical studies of two chaotic Models, representative of different mean-field potentials: a parametric random Hamiltonian and the smooth stadium. In addition, we study conductance fluctuations for different integrable confining potentials. For temperatures smaller than the mean level spacing, our results indicate that the peak height distribution is nearly always in good agreement with the available experimental data, irrespective of the confining potential (integrable or chaotic). We find that the peak bunching effect seen in the experiments is reproduced in the theoretical Models under certain special conditions. Although the Independent Particle Model fails, in general, to explain quantitatively the short-range part of the peak height correlations observed experimentally, we argue that it allows for an understanding of the long-range part.
Antoni Riera - One of the best experts on this subject based on the ideXlab platform.
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Novel Model Potential Treatment of Charge Transfer Cross Sections in C4+ and N5+ Collisions with H2
Physica Scripta, 2001Co-Authors: L. F. Errea, Jimena D. Gorfinkiel, C. Harel, H. Jouin, A Macís, L Mémdez, Bernard Pons, Antoni Riera, Pablo SanzAbstract:We present cross sections for electron capture in C4+, N5+ + H2 collisions in the energy range 50 eV/amu ≤ E ≤ 6 keV/amu, calculated using a Model potential approximation to treat the interaction of the active electron with the cores. To avoid the difficulties of the standard Independent Particle Model at low velocity, we have applied a modified technique where the Independent Particle Model is used to evaluate the matrix elements of the two-electron Hamiltonian.
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Classical treatment of collisions
Journal of Physics B: Atomic Molecular and Optical Physics, 1998Co-Authors: Clara Illescas, Antoni RieraAbstract:Using a classical treatment in the frame of an Independent Particle Model with an effective Hamiltonian, we calculate capture and ionization cross sections for collisions in the impact energy range , and compare our data with those of three sets of experiments and with those for collisions.
