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NSR database version of April 11, 2024.

Search: Author = A.S.Umar

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2023AR15      Phys.Rev. C 108, 064604 (2023)

M.Arik, S.Ayik, O.Yilmaz, A.S.Umar

Description of the multinucleon transfer mechanism for 48Ca + 244Pu and 86Kr + 198Pt reactions in a quantal transport approach

doi: 10.1103/PhysRevC.108.064604
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2023AY01      Phys.Rev. C 107, 014609 (2023)

S.Ayik, M.Arik, O.Yilmaz, B.Yilmaz, A.S.Umar

Multinucleon transfer mechanism in 250Cf + 232Th collisions using the quantal transport description based on the stochastic mean-field approach

NUCLEAR REACTIONS 232Th(250Cf, X), E(cm)=950; calculated drift path of Cf-like fragments in the head-on collision, total kinetic energy, fragments mass and charge distribution yields for different combinations of 250Cf and 232Th orientations, primary and secondary production σ, mean values of neutron and proton numbers of Cf-like fragments, diffusion coefficients. Stochastic mean field approach which provides an extension to the standard time-dependent Hartree-Fock theory by including mean-field fluctuations.

doi: 10.1103/PhysRevC.107.014609
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2023AY04      Phys.Rev. C 108, 054605 (2023)

S.Ayik, M.Arik, E.Erbayri, O.Yilmaz, A.S.Umar

Multinucleon transfer mechanism in 160Gd + 186W collisions in stochastic mean-field theory

doi: 10.1103/PhysRevC.108.054605
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2023GU19      Phys.Rev. C 108, L051602 (2023)

R.Gumbel, C.Ross, A.S.Umar

Role of isospin composition in low-energy nuclear fusion

doi: 10.1103/PhysRevC.108.L051602
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2023UM01      Phys.Rev. C 107, 064605 (2023)

A.S.Umar, K.Godbey, C.Simenel

Cluster model of 12C in the density functional theory framework

NUCLEAR STRUCTURE 12C; calculated 3-α energy surface, total density for the ground state configuration of the 3 α particles, angular momentum projection of the 12C ground state configuration, total density for the bent-arm state configuration of the 3 α particles, localization function of the bent-arm state configuration. Framework to study the cluster structures based on density constrained Hartree-Fock approach. Showed that the 12C ground state is an equilateral triangle, which has a molecular type configuration.

doi: 10.1103/PhysRevC.107.064605
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2022GO12      Phys.Rev. C 106, L051602 (2022)

K.Godbey, A.S.Umar, C.Simenel

Theoretical uncertainty quantification for heavy-ion fusion

NUCLEAR REACTIONS 48Ca(48Ca, X), E(cm)=45-61 MeV; 40Ca(40Ca, X), E(cm)=49-67 MeV; 48Ca(40Ca, X), E(cm)=46-67 MeV; 16O(208Pb, X), E(cm)=67-95 MeV; calculated fusion σ(E), theoretical model uncertainties. Quantified the uncertainties arising from uncertainties of the calculations input parameters. Density constrained time-dependent Hartree-Fock TDHF method (DC-TDHF). Comparison to experimental data.

doi: 10.1103/PhysRevC.106.L051602
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2022SU07      Phys.Rev. C 105, 034601 (2022)

X.-X.Sun, L.Guo, A.S.Umar

Microscopic study of the fusion reactions 40, 48Ca+78Ni and the effect of the tensor force

NUCLEAR REACTIONS 78Ni(40Ca, X), (48Ca, X), E(cm)=70, 80, 90 MeV; calculated internuclear potentials, fusion σ. Dynamic density-constrained time-dependent Hartree-Fock (DC-TDHF) and static Hartree-Fock theory. Discussed role of tensor force in the fusion of nuclei.

doi: 10.1103/PhysRevC.105.034601
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2021AY06      Phys.Rev. C 104, 054614 (2021)

S.Ayik, M.Arik, E.C.Karanfil, O.Yilmaz, B.Yilmaz, A.S.Umar

Quantal diffusion description of isotope production via the multinucleon transfer mechanism in 48Ca + 238U collisions

NUCLEAR REACTIONS 238U(48Ca, X), E(cm)=193 MeV; calculated neutron and proton diffusion coefficients, mean drift path of the projectile-like fragments, neutron, proton, and mixed variances as a functions of time and initial orbital angular momentum, orbital angular momentum, final average total kinetic energy (TKE), average total excitation energy, and scattering angles, mean values of mass and charge numbers of initial and final fragments, combined primary yield of multi-nucleon transfer and binary fission as function fragment mass, isotopic production σ for 238U(48Ca, X), E(cm)=193.1 MeV; calculated production σ for primary and secondary isotopes of A=150-200 Tb, Dy, Ho and Er, A=160-210 Tm, Yb, Lu and Hf, A=170-220 Ta, W, Re and Os, and A=180-230 Ir, Pt, Au and Hg. Methods involved quantal diffusion from stochastic mean-field approach, and transport properties from time-dependent single-particle wave functions of the time-dependent Hartree-Fock theory using statistical GEMINI++ code.

doi: 10.1103/PhysRevC.104.054614
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2021UM01      Phys.Rev. C 104, 034619 (2021)

A.S.Umar, C.Simenel, K.Godbey

Pauli energy contribution to the nucleus-nucleus interaction

NUCLEAR REACTIONS 40,48Ca(40Ca, X), 48Ca(48Ca, X), E not given; 208Pb(16O, X), E not given; calculated frozen neutron and proton HF density contours, nucleus-nucleus potentials from FHF, DCFHF, and DC-TDHF methods, neutron and proton contributions to the Pauli repulsion in the frozen approximation, dynamical contributions to the Pauli repulsion, proton and neutron Pauli energy and Pauli repulsion in 40Ca+40Ca system, effect of dynamical rearrangement on Pauli energy, Pauli kinetic energy (PKE) spatial distributions. Frozen Hartree Fock (FHF), density constrained frozen Hartree-Fock (DCFHF) and in the density constrained time-dependent Hartree-Fock (DC-TDHF) microscopic methods. Relevance to impact of Pauli exclusion principle on various models and approaches of calculating the interaction of two nuclei.

doi: 10.1103/PhysRevC.104.034619
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2020AY06      Phys.Rev. C 102, 024619 (2020)

S.Ayik, B.Yilmaz, O.Yilmaz, A.S.Umar

Merging of transport theory with the time-dependent Hartree-Fock approach: Multinucleon transfer in U + U collisions

NUCLEAR REACTIONS 238U(238U, X), E(cm)=833 MeV; calculated density profile and the geometry of the collisions, values of final masses and charges of the projectile-like and target-like fragments, final orbital angular momentum, total kinetic energy (TKE), total excitation energy, center of mass angle, laboratory scattering angles for tip-tip and side-side collisions, asymptotic values of the neutron, the proton and the mixed dispersions, neutron and proton diffusion coefficients, production σ(N, Z), σ(A), σ(Z) for primary fragments, production σ(A) of gold isotopes averaged over tip-tip and side-side geometries as a function of the mass numbers, and compared with experimental data. 240Cm(236Ra, X), E(cm)=833 MeV; calculated drift path of the radium-like fragments in central collisions, neutron and proton numbers of radium-like fragments as function of time, neutron and proton diffusion coefficients. Multinucleon transfer mechanism treated in the framework of quantal diffusion description based on the stochastic mean-field (SMF) properties derived from the time-dependent Hartree-Fock (TDHF) wave functions.

doi: 10.1103/PhysRevC.102.024619
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2020GO03      Phys.Rev. C 101, 034602 (2020)

K.Godbey, C.Simenel, A.S.Umar

Microscopic predictions for the production of neutron-rich nuclei in the reaction 176Yb + 176Yb

NUCLEAR REACTIONS 176Yb(176Yb, X), E(cm)=660, 880 MeV; calculated scattering angles, total kinetic energies of the outgoing fragments, particle number fluctuations and correlations, mass-angle and mass-energy distributions, primary fragments production σ(E), production σ(E) of NZ, ZZ and NN nuclei using time-dependent Hartree-Fock (TDHF) calculations and its time-dependent random-phase approximation (TDRPA) extension for scattering and multi-nucleon transfer (MNT) characteristics. Relevance to r process in nuclear astrophysical models.

doi: 10.1103/PhysRevC.101.034602
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2020HU08      Phys.Rev. C 101, 061601 (2020)

S.Hudan, R.T.deSouza, A.S.Umar, Z.Lin, C.J.Horowitz

Enhanced dynamics in fusion of neutron-rich oxygen nuclei at above-barrier energies

NUCLEAR REACTIONS 12C(16O, X), (17O, X), (18O, X), (19O, X), E(cm)=7-20 MeV; calculated above-barrier fusion σ(E) using static and dynamical microscopic model. Comparison with experimental data, and with CCFULL, TDHF and FHF calculations.

doi: 10.1103/PhysRevC.101.061601
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2020SI08      Phys.Rev.Lett. 124, 212504 (2020)

C.Simenel, K.Godbey, A.S.Umar

Timescales of Quantum Equilibration, Dissipation and Fluctuation in Nuclear Collisions

NUCLEAR REACTIONS 238U(40Ca, X), 249Bk(48Ca, X), (50Ti, X), 186W(54Cr, X), E not given; analyzed available data; calculated timescales in collisions of atomic nuclei using fully microscopic approaches using time-dependent Hartree-Fock and time-dependent random-phase approximation.

doi: 10.1103/PhysRevLett.124.212504
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2020ZH02      Phys.Lett. B 801, 135170 (2020), Corrigendum Phys.Lett. B 803, 135278 (2020)

N.T.Zhang, X.Y.Wang, D.Tudor, B.Bucher, I.Burducea, H.Chen, Z.J.Chen, D.Chesneanu, A.I.Chilug, L.R.Gasques, D.G.Ghita, C.Gomoiu, K.Hagino, S.Kubono, Y.J.Li, C.J.Lin, W.P.Lin, R.Margineanu, A.Pantelica, I.C.Stefanescu, M.Straticiuc, X.D.Tang, L.Trache, A.S.Umar, W.Y.Xin, S.W.Xu, Y.Xu

Constraining the 12C+12C astrophysical S-factors with the 12C+13C measurements at very low energies

NUCLEAR REACTIONS 12C(13C, p)24Na, E=4.640-10.995 MeV; measured reaction products, Eγ, Iγ; deduced σ, branching ratio, S-factor.

doi: 10.1016/j.physletb.2019.135170
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Data from this article have been entered in the EXFOR database. For more information, access X4 datasetD0970.

2019AY02      Phys.Rev. C 100, 014609 (2019)

S.Ayik, B.Yilmaz, O.Yilmaz, A.S.Umar

Quantal diffusion approach for multinucleon transfers in Xe + Pb collisions

NUCLEAR REACTIONS 136Xe(208Pb, X), 130Te(214Po, X), 138Ce(206Pt, X), E(cm)=526 MeV; calculated distribution of projectile-like and target-like reaction product by mass number and charge for 208Pb+136Xe reaction, neutron and proton diffusion coefficients and drift paths using quantal diffusion approach.

doi: 10.1103/PhysRevC.100.014609
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2019AY06      Phys.Rev. C 100, 044614 (2019)

S.Ayik, O.Yilmaz, B.Yilmaz, A.S.Umar

Heavy-isotope production in 136Xe 208Pb collisions at Ec.m. = 514 MeV

NUCLEAR REACTIONS 208Pb(136Xe, X)210Po/222Rn/224Ra, E(cm)=514 MeV; calculated TKE, excitation energy, scattering angles, mass dispersions toward asymmetry and symmetry directions, production σ for A=110-230 isotopes, and for primary isotopes of Z=84, 86 and 88 as a function of mass number using stochastic mean field (SMF) approach. Comparison with experimental data.

doi: 10.1103/PhysRevC.100.044614
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2019GO17      Phys.Rev. C 100, 024610 (2019)

K.Godbey, A.S.Umar, C.Simenel

Deformed shell effects in 48Ca + 249Bk quasifission fragments

NUCLEAR REACTIONS 249Bk(48Ca, X), E(cm)=234 MeV; calculated total kinetic energies of quasifission fragments as a function of their mass ratio and compared to Viola systematics, mass-angle correlations, yields of fragments by mass, proton and neutron numbers, distribution of scattering angle as function of mass ratio, proton and neutron numbers using time-dependent Hartree-Fock simulations. Influence of shell effects, and orientation of the deformed target in the entrance channel in the formation of the fragments. Relevance to optimization of entrance channels for the formation of superheavy nuclei (SHN).

doi: 10.1103/PhysRevC.100.024610
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2019GO18      Phys.Rev. C 100, 024619 (2019)

K.Godbey, C.Simenel, A.S.Umar

Absence of hindrance in a microscopic 12C + 12C fusion study

NUCLEAR REACTIONS 12C(12C, X), E(cm)=2-12 MeV; calculated fusion σ(E) and astrophysical S(E) factors using a static Hartree-Fock and time-dependent Hartree-Fock mean-field method; no S factor maximum observed, and no extreme sub-barrier hindrance predicted at low energies. Comparison with experimental data.

doi: 10.1103/PhysRevC.100.024619
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2019GO28      Phys.Rev. C 100, 054612 (2019)

K.Godbey, L.Guo, A.S.Umar

Influence of the tensor interaction on heavy-ion fusion cross sections

NUCLEAR REACTIONS 12C(12C, X), (13C, X), E(cm)=1-7 MeV; 40Ca(40Ca, X), (48Ca, X), 48Ca(48Ca, X), E(cm)=46-59 MeV; 48Ca(48Ca, X), E(cm)=45-63 MeV; 48Ca(110Sn, X), (116Sn, X), (120Sn, X), E(cm)=106-130 MeV; 208Pb(16O, X), E(cm)=69-84 MeV; calculated fusion σ(E), and S factors for 12C reactions using the fully microscopic density constrained time-dependent Hartree-Fock (DC-TDHF) method with the Skyrme SLy5 and SLy5t tensor interactions; deduced that inclusion of tensor interaction has measurable effect on the fusion cross sections.

doi: 10.1103/PhysRevC.100.054612
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2018AY03      Phys.Rev. C 97, 054618 (2018)

S.Ayik, B.Yilmaz, O.Yilmaz, A.S.Umar

Quantal diffusion description of multinucleon transfers in heavy-ion collisions

NUCLEAR REACTIONS 238U(48Ca, X), E(cm)=193 MeV; calculated collision density profile, neutron and proton mean-drift path, drift and diffusion coefficients, curvature parameters, covariance of fragment mass distribution, impact parameter, final orbital angular momentum, final average total kinetic energy TKE, average total excitation energy, scattering angles, mass and charge numbers of final fragments, yield and production cross section of primary fragments. Stochastic mean-field (SMF) approach with a quantal diffusion description of the multi-nucleon transfer in heavy-ion collisions at finite impact parameters. Comparison with experimental data.

doi: 10.1103/PhysRevC.97.054618
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2018GU20      Phys.Rev. C 98, 064607 (2018)

L.Guo, K.Godbey, A.S.Umar

Influence of the tensor force on the microscopic heavy-ion interaction potential

NUCLEAR REACTIONS 12C(12C, X), E(cm)=8 MeV; 16O(16O, X), E(cm)=12 MeV; 40Ca(40Ca, X), E(cm)=55 MeV; 40,48Ca(48Ca, X), E(cm)=55 MeV; 56Ni(56Ni, X), E(cm)=105 MeV; 56Ni(48Ca, X), E(cm)=75; 100,116,120Sn(48Ca, X), E(cm)=125 MeV; calculated internuclear potentials with and without Skyrme tensor force using static Hartree-Fock and dynamic density-constrained time-dependent Hartree-Fock (DC-TDHF) theory. Discussed role of tensor force in the fusion of nuclei.

doi: 10.1103/PhysRevC.98.064607
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2018SI24      Prog.Part.Nucl.Phys. 103, 19 (2018)

C.Simenel, A.S.Umar

Heavy-ion collisions and fission dynamics with the time-dependent Hartree-Fock theory and its extensions

doi: 10.1016/j.ppnp.2018.07.002
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2018UM01      Acta Phys.Pol. B49, 573 (2018)

A.S.Umar, C.Simenel

TDHF Investigations of the U+U Quasifission Process

NUCLEAR REACTIONS 238U(238U, x), E(cm)=850-1350 MeV; calculated possibilities of reaching high-Z rich isotopes using unrestricted TDHF, Skyrme Hartree-Fock, Quantum Molecular Dynamics (QMD), Improved QMD (ImQMD), Dinuclear Nuclear System (DNS), Relativistic Mean-Field (RMF), Time-Dependent Hartree-Fock (TDHF), Density Constrained TDHF (DC-TDHF)(evaporation residue σ strongly reduced due to Quasifission (QF) and Fusion-Fission (FF)); calculated evolution of central collisions, reaching (in tip-side oriented collision) exit heavy fragment of Z≈ 194 and A≈325, nuclear contact time for E(cm)=850-1350 MeV for tip-side and tip-tip orientations, also with ternary fission possibility and shown with the ternary fragment of Z≈7 shown in the calculations; calculated final E* vs E at central collisions.

doi: 10.5506/aphyspolb.49.573
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2018UM02      Nuovo Cim. C 41, 173 (2018)

A.S.Umar, C.Simenel, K.Godbey

Equilibration dynamics and isospin effects in nuclear reactions

NUCLEAR REACTIONS 249Bk(48Ca, X), E(cm)=234 MeV; 186W(54Cr, X), E(cm)=218.6 MeV; 208Pb(78Kr, X), E=8.5 MeV/nucleon; analyzed available data; calculated equilibration times for mass, isospin, and TKE (total kinetic energy). TDFHF approach.

doi: 10.1393/ncc/i2018-18173-9
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2018YI04      Phys.Rev. C 98, 034604 (2018)

B.Yilmaz, S.Ayik, O.Yilmaz, A.S.Umar

Multinucleon transfer in 58Ni + 60Ni and 60Ni + 60Ni in a stochastic mean-field approach

NUCLEAR REACTIONS 60Ni(58Ni, X), (60Ni, X), E(cm)=135.6 MeV; calculated density profiles, neutron and proton diffusion coefficients, one-sided mean drift paths, collision covariances, dispersion per unit mass, and fragment mass distribution using stochastic mean-field (SMF) approach. Comparison with experimental values and time-dependent random-phase approximation (TDRPA) calculations.

doi: 10.1103/PhysRevC.98.034604
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2017AY05      Phys.Rev. C 96, 024611 (2017)

S.Ayik, B.Yilmaz, O.Yilmaz, A.S.Umar, G.Turan

Multinucleon transfer in central collisions of 238U + 238U

NUCLEAR REACTIONS 238U(238U, X), E(cm)=900, 1050 MeV; calculated density profiles in the reaction plane, and mean drift path of the projectile-like fragments using time-dependent Hartree-Fock (TDHF) approach, quantal neutron and proton diffusion coefficients, memory effects and covariances, primary fragment mass distributions using stochastic mean-field (SMF) approach.

doi: 10.1103/PhysRevC.96.024611
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2017GO03      Phys.Rev. C 95, 011601 (2017)

K.Godbey, A.S.Umar, C.Simenel

Dependence of fusion on isospin dynamics

NUCLEAR REACTIONS 48Ca(40Ca, X), E(cm)=55 MeV; 208Pb(16O, X), E(cm)=75, 90, 120 MeV; 208Pb(48Ca, X), (50Ti, X), E(cm)/VB=1.065; 40,48Ca(132Sn, X), E(cm)=75 MeV; calculated total and isoscalar density-constrained time-dependent Hartree-Fock (DC-TDHF) potentials. 40Ca(132Sn, X), E(cm)=108-140 MeV; calculated fusion σ(E). Time-dependent Hartree-Fock theory and isoscalar and isovector properties of energy density functional (EDF).

doi: 10.1103/PhysRevC.95.011601
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2017SI03      Phys.Lett. B 765, 99 (2017)

V.Singh, J.Vadas, T.K.Steinbach, B.B.Wiggins, S.Hudan, R.T.deSouza, Z.Lin, C.J.Horowitz, L.T.Baby, S.A.Kuvin, V.Tripathi, I.Wiedenhover, A.S.Umar

Fusion enhancement at near and sub-barrier energies in 19O + 12C

NUCLEAR REACTIONS 12C(18O, X), (19O, X), E(cm)<20 MeV; measured reaction products; deduced σ. comparison with a state-of-the-art microscopic model.

doi: 10.1016/j.physletb.2016.12.017
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Data from this article have been entered in the EXFOR database. For more information, access X4 datasetC2257.

2017SI06      Phys.Rev. C 95, 031601 (2017)

C.Simenel, A.S.Umar, K.Godbey, M.Dasgupta, D.J.Hinde

How the Pauli exclusion principle affects fusion of atomic nuclei

NUCLEAR REACTIONS 40Ca(40Ca, X), E(cm)=48-64 MeV; 48Ca(48Ca, X), E(cm)=45-61 MeV; 208Pb(16O, X), E(cm)=65-90 MeV; calculated nucleus-nucleus potentials with and without Pauli exclusion principle, fusion σ(E), FHF and DCFHF σ(E) without couplings. 16O(16O, X), 40Ca(40Ca, X), 48Ca(40Ca, X), 208Pb(48Ca, X); calculated nucleus-nucleus potentials without (FHF) and with (DCFHF) Pauli exclusion principle. Coupled-channel calculations using CCFULL code, and Woods-Saxon fits of the Frozen Hartree-Fock (FHF) and density-constrained frozen Hartree-Fock (DCFHF) potentials. Comparison with experimental data.

doi: 10.1103/PhysRevC.95.031601
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2017UM01      Phys.Rev. C 96, 024625 (2017)

A.S.Umar, C.Simenel, W.Ye

Transport properties of isospin asymmetric nuclear matter using the time-dependent Hartree-Fock method

NUCLEAR REACTIONS 208Pb(78Kr, X), (92Kr, X), E=8.5 MeV/nucleon; calculated impact parameter and energy-loss dependence of relevant observables, neutron and proton numbers transferred to and from the projectile-like fragments (PLFs), neutron and proton numbers of the PLFs as a function of impact parameter and the angle representing initial orientation of deformed projectile with respect to the beam axis, deflection functions, final kinetic energy versus the scattering angle for the reactions, sticking time as a function of impact parameter, N/Z values for PLFs and target-like fragments (TLFs) as a function of energy loss, (N-Z)/A values of primary PLFs and TLFs as function of contact time between the collision partners, distribution of PLF neutron and proton numbers in the N-Z plane, percent of total excitation energy carried by the PLFs as a function of energy loss. Time-dependent density-constrained Hartree-Fock (TDHF) method in full three dimensions.

doi: 10.1103/PhysRevC.96.024625
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2016AY06      Phys.Rev. C 94, 044624 (2016)

S.Ayik, O.Yilmaz, B.Yilmaz, A.S.Umar

Quantal nucleon diffusion: Central collisions of symmetric nuclei

NUCLEAR REACTIONS 28O(28O, X), E(cm)=8.7 MeV; 40Ca(40Ca, X), E(cm)=52.7 MeV; 48Ca(48Ca, X), E(cm)=50.7 MeV; 56Ni(56Ni, X), E(cm)=100.0 MeV; calculated quantal and semiclassical neutron and proton diffusion coefficients, effect of Pauli blocking on fragment neutron and proton variances using stochastic mean-field (SMF) approach.

doi: 10.1103/PhysRevC.94.044624
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2016RE07      Phys.Rev. C 93, 044618 (2016)

P.-G.Reinhard, A.S.Umar, P.D.Stevenson, J.Piekarewicz, V.E.Oberacker, J.A.Maruhn

Sensitivity of the fusion cross section to the density dependence of the symmetry energy

NUCLEAR REACTIONS 48Ca(48Ca, X)96Zr*, E(cm)=45-65 MeV; calculated folding model ion-ion interaction potentials, fusion σ(E). Impact of nuclear fusion on the nuclear equation of state (EOS). 48Ca; calculated Neutron root-mean-square radius (rms), neutron diffraction radius, and neutron halo. Dynamic microscopic method based on density-constrained time-dependent Hartree-Fock (DC-TDHF) approach, and direct TDHF study of barrier cross sections using a family of Skyrme parametrization.

doi: 10.1103/PhysRevC.93.044618
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2016ST13      Phys.Rev. C 93, 054617 (2016)

P.D.Stevenson, E.B.Suckling, S.Fracasso, M.C.Barton, A.S.Umar

Skyrme tensor force in heavy ion collisions

NUCLEAR REACTIONS 16O(16O, X), E(cm)=100 MeV; calculated contributions from terms involving time-odd densities and currents to the total energy as the sum of isoscalar and isovector contributions, energy contributions from (pseudo)scalar-, vector- and (pseudo)tensor-decomposed form of spin-current tensor J. Symmetry-unrestricted Time-dependent Hartree-Fock (TDHF) energy density functional calculations with full version of Skyrme force, including terms arising only from the Skyrme tensor force. Discussed role of Skyrme tensor force in dynamic processes in nuclei.

doi: 10.1103/PhysRevC.93.054617
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2016TO05      Phys.Rev. C 93, 034607 (2016)

M.Tohyama, A.S.Umar

Two-body dissipation effects on the synthesis of superheavy elements

NUCLEAR REACTIONS 208Pb(82Ge, X), E(cm)=284, 292-388, 468-626 MeV; 208Pb(84Se, X), E(cm)=299, 298-403 MeV; 208Pb(86Kr, X), E(cm)=341 MeV; 208Pb(88Sr, X), E(cm)=340 MeV; calculated contour density plots for low-energy head-on collisions. Synthesis of superheavy elements. Time-dependent density-matrix theory (TDDM), as an extension of the time-dependent Hartree-Fock (TDHF) theory.

doi: 10.1103/PhysRevC.93.034607
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2016UM04      Phys.Rev. C 94, 024605 (2016)

A.S.Umar, V.E.Oberacker, C.Simenel

Fusion and quasifission dynamics in the reactions 48Ca + 249Bk and 50Ti + 249Bk using a time-dependent Hartree-Fock approach

NUCLEAR REACTIONS 249Bk(48Ca, X), E(cm)=211, 218, 193-230 MeV; 249Bk(50Ti, X), E(cm)=233.2, 205-245 MeV; calculated contact time, mass and charge of the light fragment, and excitation energies of the heavy and light fragments as function of incident energy, mass-angle and mass-TKE distributions. Unrestricted time-dependent Hartree-Fock (TDHF) calculations, and the density-constrained TDHF method to extract NN potentials and excitation energy in each fragment. Relevance to the production of Z=117 and 119 superheavy elements, and fusion and quasifission processes.

doi: 10.1103/PhysRevC.94.024605
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2015AY03      Phys.Rev. C 91, 054601 (2015)

S.Ayik, O.Yilmaz, B.Yilmaz, A.S.Umar, A.Gokalp, G.Turan, D.Lacroix

Quantal description of nucleon exchange in a stochastic mean-field approach

NUCLEAR REACTIONS 40Ca(40Ca, X), E(cm)=52.7 MeV; 48Ca(48Ca, X), E(cm)=50.7 MeV; 56Ni(56Ni, X), E(cm)=99.9 MeV; calculated quantal diffusion coefficient and variance of fragment mass distribution as a function of time in central collision. Stochastic mean-field approach. Comparison with other theoretical calculations.

doi: 10.1103/PhysRevC.91.054601
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2015HA12      Phys.Rev. C 91, 041602 (2015)

K.Hammerton, Z.Kohley, D.J.Hinde, M.Dasgupta, A.Wakhle, E.Williams, V.E.Oberacker, A.S.Umar, I.P.Carter, K.J.Cook, J.Greene, D.Y.Jeung, D.H.Luong, S.D.McNeil, C.S.Palshetkar, D.C.Rafferty, C.Simenel, K.Stiefel

Reduced quasifission competition in fusion reactions forming neutron-rich heavy elements

NUCLEAR REACTIONS 180W(50Cr, X), E(cm)=222.6 MeV; 180W(52Cr, X), E(cm)=221.2 MeV; 180W(54Cr, X), E(cm)=219.8 MeV; 186W(50Cr, X), E(cm)=221.0 MeV; 184W(52Cr, X), E(cm)=220.1 MeV; 182W(54Cr, X), E(cm)=221.0 MeV; 184W(54Cr, X), E(cm)=218.9 MeV; 186W(54Cr, X), E(cm)=218.3 MeV; measured spectra of neutron-rich fragments from fusion-fission and quasifission in coincidence mode, mass-angle distributions (MADs) using the ANU CUBE detector system at ANU's Heavy-Ion Accelerator Facility; deduced strong dependence on the N/Z of the compound system in quasifission system. Comparison with microscopic time-dependent Hartree-Fock calculations of the quasifission process.

doi: 10.1103/PhysRevC.91.041602
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2015UM02      Phys.Rev. C 92, 024621 (2015)

A.S.Umar, V.E.Oberacker, C.Simenel

Shape evolution and collective dynamics of quasifission in the time-dependent Hartree-Fock approach

NUCLEAR REACTIONS 238U(40Ca, X), E(cm)=211 MeV; 249Bk(48Ca, X), E(cm)=218 MeV; 238U(48Ca, X), E(cm)=203 MeV; calculated effect of moment of inertia on the angular distribution of the fragments, contour plot of the time evolution of the mass density for 249Bk+48Ca reaction, time dependence on the moments inertia, impact parameter and temperature using fully microscopic time-dependent Hartee-Fock (TDHF) approach.

doi: 10.1103/PhysRevC.92.024621
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2015UM03      Phys.Rev. C 92, 025808 (2015)

A.S.Umar, V.E.Oberacker, C.J.Horowitz, P.-G.Reinhard, J.A.Maruhn

Swelling of nuclei embedded in neutron-gas and consequences for fusion

NUCLEAR REACTIONS 28O(28O, X), E(cm)=2-14 MeV; 60Ca(60Ca, X), E(cm)=34-58 MeV; calculated pycnonuclear fusion cross sections and Astrophysical S factor as a function of external neutron-gas density, up to 500 neutrons for 28O and 1040 for 60Ca using Sao Paulo potential and incoming wave boundary condition (IWBC) method. Relevance to study of fusion of neutron rich nuclei at radioactive ion beam facilities, and to the study of composition and heating of the crust of accreting neutron stars.

doi: 10.1103/PhysRevC.92.025808
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2015UM04      Nucl.Phys. A944, 238 (2015)

A.S.Umar, V.E.Oberacker

Time-dependent HF approach to SHE dynamics

NUCLEAR REACTIONS 238U(48Ca, x), E(cm)=185-250 MeV; calculated potential barrier for different mutual orientation of colliding nuclei, capture σ, deformation time dependence, inertia moment time dependence, light fragment charge and mass. 186W(54Cr, x), E=218.6 MeV;238U(40Ca, x), E(cm)=208-220 MeV; calculated quasifission time development for different mutual orientation of colliding nuclei, deformation, TKE, orientation angle between the nuclei, mass and charge differences, moment of inertia. DC-TDHF (Density Constrained TDHF). Compared with available data.

doi: 10.1016/j.nuclphysa.2015.02.011
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2014OB06      Phys.Rev. C 90, 054605 (2014)

V.E.Oberacker, A.S.Umar, C.Simenel

Dissipative dynamics in quasifission

NUCLEAR REACTIONS 238U(40Ca, X), (48Ca, X), E(cm)=209 MeV; calculated contact time, mass and charge of light fragment as function of impact parameter, total kinetic energy (TKE) of the quasifission (QF) fragments. Evidence of less QF in 48Ca+238U system than in 40Ca+238U, relevance to formation of superheavy elements (SHE). Discussed the effect due to magicity of 48Ca. TDHF calculations with Skyrme SLy4d energy density functional (EDF).

doi: 10.1103/PhysRevC.90.054605
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2014SI06      Phys.Rev. C 89, 031601 (2014)

C.Simenel, A.S.Umar

Formation and dynamics of fission fragments

RADIOACTIVITY 258,264Fm(SF); calculated adiabatic fission potential for symmetric fission as function of distance between fragments, time evolution of various energies using realistic mean-field computer codes, and time-dependent Hartree-Fock (TDHF) method.

doi: 10.1103/PhysRevC.89.031601
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2014ST22      Phys.Rev. C 90, 041603 (2014)

T.K.Steinbach, J.Vadas, J.Schmidt, C.Haycraft, S.Hudan, R.T.deSouza, L.T.Baby, S.A.Kuvin, I.Wiedenhover, A.S.Umar, V.E.Oberacker

Sub-barrier enhancement of fusion as compared to a microscopic method in 18O + 12C

NUCLEAR REACTIONS 12C(18O, X), E=16.25, 36 MeV; measured fragment spectra, fusion σ(E) in sub-barrier domain, time-of-flight (TOF) technique at FSU tandem accelerator facility. Pulsed beam. Comparison with previous experimental results, and with density-constrained time-dependent Hartree-Fock (DC-TDHF) and coupled channel calculations.

doi: 10.1103/PhysRevC.90.041603
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Data from this article have been entered in the EXFOR database. For more information, access X4 datasetC2142.

2014UM01      Phys.Rev. C 89, 034611 (2014)

A.S.Umar, C.Simenel, V.E.Oberacker

Energy dependence of potential barriers and its effect on fusion cross sections

NUCLEAR REACTIONS 40Ca(40Ca, X), E(cm)=50, 53, 60, 65 MeV; 208Pb(16O, X), E(cm)=75, 80, 100 MeV; calculated ion-ion interaction potentials, fusion σ(E), fusion barrier distributions as function of incident energy. Density-constrained and direct time-dependent Hartree-Fock (DC-TDHF) methods. Comparison with experimental data.

doi: 10.1103/PhysRevC.89.034611
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2013DE23      Phys.Rev. C 88, 014602 (2013)

R.T.deSouza, S.Hudan, V.E.Oberacker, A.S.Umar

Confronting measured near- and sub-barrier fusion cross sections for 20O+12C with a microscopic method

NUCLEAR REACTIONS 12C(20O, X), E(cm)=6-16 MeV; calculated total fusion cross section, heavy-ion potentials, averaged fusion σ. Density-constrained time-dependent Hartree-Fock (DC-TDHF) microscopic method. Comparison with σ measurements for an experiment at SPIRAL-1, GANIL facility at E(20O)=1-2 MeV/nucleon. Comparison with other theoretical calculations.

doi: 10.1103/PhysRevC.88.014602
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2013OB01      Phys.Rev. C 87, 034611 (2013)

V.E.Oberacker, A.S.Umar

Microscopic analysis of sub-barrier fusion enhancement in 132Sn+40Ca versus 132Sn+48Ca

NUCLEAR REACTIONS 132Sn(40Ca, X), (48Ca, X), E(cm)=106-140 MeV; calculated heavy-ion potential, total fusion σ(E). Microscopic calculations based on density-constrained time-dependent Hartree-Fock theory (DC-TDHF) using Skyrme SLy4 interaction. Comparison with experimental data.

doi: 10.1103/PhysRevC.87.034611
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2013SI21      Phys.Rev. C 88, 024617 (2013)

C.Simenel, R.Keser, A.S.Umar, V.E.Oberacker

Microscopic study of 16O+16O fusion

NUCLEAR REACTIONS 16O(16O, X), E(cm)=6-40 MeV; calculated fusion σ(E) using three dimensional time-dependent Hartree-Fock (TDHF), and density-constrained time-dependent Hartree Fock (DC-TDHF) calculations. 16O(16O, X), E(cm)=6-13 MeV; calculated fusion σ(E) with no coupling and couplings to first 3- states in one or both nuclei using coupled-channel approach (CCFULL computer code). Discussed role of coupling to low-lying octupole states. Comparison with experimental data.

doi: 10.1103/PhysRevC.88.024617
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2012KE03      Phys.Rev. C 85, 044606 (2012)

R.Keser, A.S.Umar, V.E.Oberacker

Microscopic study of Ca + Ca fusion

NUCLEAR REACTIONS 40Ca(40Ca, X), 48Ca(40Ca, X), (48Ca, X), E(cm)=45-65; calculated total fusion σ(E), potential barriers, neutron and proton transfer, and excitation energy as a function of the ion-ion distance, isoscalar deformation parameter, power spectrum of isovector dipole amplitude. Microscopic time-dependent Hartree-Fock theory with density constraint (DC-TDHF). Comparison with experimental data.

doi: 10.1103/PhysRevC.85.044606
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2012LO10      Phys.Rev. C 86, 024608 (2012)

N.Loebl, A.S.Umar, J.A.Maruhn, P.-G.Reinhard, P.D.Stevenson, V.E.Oberacker

Single-particle dissipation in a time-dependent Hartree-Fock approach studied from a phase-space perspective

NUCLEAR REACTIONS 40Ca(40Ca, X), E(cm)=160, 200, 240 MeV; calculated β and γ deformation parameter, quadrupole moment, and volume phase-space global observables in momentum and coordinate space using the time-dependent Hartree-Fock (TDHF) theory and the Wigner distribution function in the full six-dimensional phase space. Significance of extra time-odd terms.

doi: 10.1103/PhysRevC.86.024608
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2012OB02      Phys.Rev. C 85, 034609 (2012)

V.E.Oberacker, A.S.Umar, J.A.Maruhn, P.-G.Reinhard

Dynamic microscopic study of pre-equilibrium giant resonance excitation and fusion in the reactions 132Sn + 48Ca and 124Sn + 40Ca

NUCLEAR REACTIONS 132Sn(48Ca, X), 124Sn(40Ca, X), E(cm)=130 MeV; calculated time evolution of isoscalar quadrupole moment, deformation parameter and rms charge radius, isovector quadrupole moment, dipole amplitude, neutron leakage, pre-equilibrium dipole radiation spectrum, total fusion cross sections, heavy-ion potential, microscopic mass parameter. Pre-equilibrium Giant dipole resonance (GDR) excitation. Density-constrained time-dependent Hartree-Fock (TDHF) method. Comparison with experimental data.

doi: 10.1103/PhysRevC.85.034609
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2012UM01      Phys.Rev. C 85, 017602 (2012)

A.S.Umar, V.E.Oberacker, J.A.Maruhn, P.-G.Reinhard

Microscopic composition of ion-ion interaction potentials

NUCLEAR REACTIONS 16O(16O, X), (24O, X), E(cm)=12 MeV; 40Ca(40Ca, X), E(cm)=55 MeV; 132Sn(48Ca, X), E(cm)=120 MeV; calculated ion-ion interaction potentials for head-on collisions using TDHF approach for the time evolution of the nuclear collision.

doi: 10.1103/PhysRevC.85.017602
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2012UM02      Phys.Rev. C 85, 055801 (2012)

A.S.Umar, V.E.Oberacker, C.J.Horowitz

Microscopic sub-barrier fusion calculations for the neutron star crust

NUCLEAR REACTIONS 12C, 16,24,28O(16O, X), (24O, X), E(cm)=2-13 MeV; calculated nuclear density contours, potential barriers, fusion σ(E), astrophysical S factor. Time-dependent Hartree-Fock theory with density-constrained Hartree-Fock calculations. Comparison with Sao Paulo static barrier penetration model and experimental data.

doi: 10.1103/PhysRevC.85.055801
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2011RE05      Phys.Rev. C 83, 034312 (2011)

P.-G.Reinhard, J.A.Maruhn, A.S.Umar, V.E.Oberacker

Localization in light nuclei

NUCLEAR STRUCTURE 4He, 8Be, 12,20C, 16O, 20Ne, 24Mg, 28Si; calculated contours of proton localization and total density. Spatial localization of light nuclei within the Hartree-Fock approximation.

doi: 10.1103/PhysRevC.83.034312
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2010OB01      Phys.Rev. C 82, 034603 (2010)

V.E.Oberacker, A.S.Umar, J.A.Maruhn, P.-G.Reinhard

Microscopic study of the 132, 124Sn+96Zr reactions: Dynamic excitation energy, energy-dependent heavy-ion potential, and capture cross section

NUCLEAR REACTIONS 96Zr(124Sn, X), (132Sn, X), (134Sn, X), E(cm)=195-260 MeV; calculated mass density contour plots, potential barriers, intrinsic mass quadrupole moment, heavy ion potential barriers, precompound excitation energy, capture and inelastic cross sections using time-dependent Hartree-Fock (TDHF) and density-constrained time-dependent Hartree-Fock methods (DC-TDHF).

doi: 10.1103/PhysRevC.82.034603
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2010UM01      Phys.Rev.Lett. 104, 212503 (2010)

A.S.Umar, J.A.Maruhn, N.Itagaki, V.E.Oberacker

Microscopic Study of the Triple-α Reaction

NUCLEAR REACTIONS 8Be(α, X)12C, E(cm)=2 MeV; calculated time evolution, potential energy curves for 4He + 8Be head-n collision, single-particle parities of the neutron states; deduced formation of a metastable linear chain state of three α-like clusters. Time-dependent Hartree-Fock theory.

doi: 10.1103/PhysRevLett.104.212503
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2010UM02      Phys.Rev. C 81, 064607 (2010)

A.S.Umar, V.E.Oberacker, J.A.Maruhn, P.-G.Reinhard

Entrance channel dynamics of hot and cold fusion reactions leading to superheavy elements

NUCLEAR REACTIONS 208Pb(70Zn, X), E(cm)=260-350 MeV; 238U(48Ca, X), E(cm)=180-250 MeV; calculated potential barriers, excitation energies, and capture σ using fully microscopic time-dependent Hartree-Fock theory coupled with a density constraint. Comparison with experimental data.

doi: 10.1103/PhysRevC.81.064607
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2009UM01      J.Phys.(London) G36, 025101 (2009)

A.S.Umar, V.E.Oberacker

Center-of-mass motion and cross-channel coupling in the time-dependent Hartree-Fock theory

doi: 10.1088/0954-3899/36/2/025101
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2009UM03      Eur.Phys.J. A 39, 243 (2009)

A.S.Umar, V.E.Oberacker

Density-constrained time-dependent Hartree-Fock calculation of 16O + 208Pb fusion cross-sections

NUCLEAR REACTIONS 208Pb(16O, X), E(cm)=65-110 MeV; calculated total fusion σ using energy-dependent density-constrained time-dependent Hartree-Fock method. Comparison with data.

doi: 10.1140/epja/i2008-10712-5
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2009UM04      Phys.Rev. C 80, 041601 (2009)

A.S.Umar, V.E.Oberacker, J.A.Maruhn, P.-G.Reinhard

Microscopic calculation of pre-compound excitation energies for heavy-ion collisions

NUCLEAR REACTIONS 16O(16O, X), E(cm)=11, 20, 34, 50 MeV; 34Ne(16O, X), E(cm)=11, 15, 30 MeV; 40Ca(40Ca, X), E(cm)=55, 60, 80, 100 MeV;calculated excitation energies, internuclear potentials, and ion-ion potentials for head-on collisions using time-dependent Hartree-Fock (TDHF) theory.

doi: 10.1103/PhysRevC.80.041601
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2008UM03      Phys.Rev. C 77, 064605 (2008)

A.S.Umar, V.E.Oberacker

64Ni+64Ni fusion reaction calculated with the density-constrained time-dependent Hartree-Fock formalism

NUCLEAR REACTIONS 64Ni(64Ni, X), E(cm)=86-110 MeV; calculated orientation probabilities, potential barriers, density contours, σ. Time-dependent Hartree-Fock model.

doi: 10.1103/PhysRevC.77.064605
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2008UM04      Eur.Phys.J. A 37, 245 (2008)

A.S.Umar, V.E.Oberacker, J.A.Maruhn

Neutron transfer dynamics and doorway to fusion in time-dependent Hartree-Fock theory

NUCLEAR REACTIONS 24O(16O, X), E(cm)=7, 8, 9 MeV; 96Zr(40Ca, X), E(cm)=91, 97 MeV; calculated neutron and single-particle probability densities, potential barrier using time-dependent Hartree-Fock model.

doi: 10.1140/epja/i2008-10614-6
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2007UM02      Phys.Rev. C 76, 014614 (2007)

A.S.Umar, V.E.Oberacker

64Ni+132Sn fusion within the density-constrained time-dependent Hartree-Fock formalism

NUCLEAR REACTIONS 132Sn(64Ni, f)E(cm)<200 MeV; calculated fusion cross sections using the density constrained time-dependent Hartree-Fock formalism.

doi: 10.1103/PhysRevC.76.014614
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2007UM03      Phys.Rev. C 76, 024316 (2007)

A.S.Umar, V.E.Oberacker

Compressibility and equation of state of finite nuclei

doi: 10.1103/PhysRevC.76.024316
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2006UM02      Phys.Rev. C 73, 054607 (2006)

A.S.Umar, V.E.Oberacker

Three-dimensional unrestricted time-dependent Hartree-Fock fusion calculations using the full Skyrme interaction

NUCLEAR REACTIONS 16O(16O, X), E(cm)=34 MeV; calculated fusion σ. Three-dimensional unrestricted time-dependent Hartree-Fock approach, Skyrme interaction.

doi: 10.1103/PhysRevC.73.054607
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2006UM03      Phys.Rev. C 74, 021601 (2006)

A.S.Umar, V.E.Oberacker

Heavy-ion interaction potential deduced from density-constrained time-dependent Hartree-Fock calculation

NUCLEAR REACTIONS 16O(16O, X), E(cm)=34 MeV; 22Ne(16O, X), E(cm)=50 MeV; calculated internuclear potentials. Density-constrained time-dependent Hartree-Fock calculation.

doi: 10.1103/PhysRevC.74.021601
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2006UM04      Phys.Rev. C 74, 024606 (2006)

A.S.Umar, V.E.Oberacker

Time dependent Hartree-Fock fusion calculations for spherical, deformed systems

NUCLEAR REACTIONS 162Dy(64Ni, 64Ni'), E(cm)=200, 265 MeV; calculated Coulomb excitation probabilities for ground-state rotational band, dynamic alignment features. 22Ne(16O, X), E(cm)=95 MeV; calculated dynamic alignment due to Coulomb excitation, fusion σ vs orientation. Time dependent Hartree-Fock approach.

doi: 10.1103/PhysRevC.74.024606
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2006UM06      Phys.Rev.C 74, 061601 (2006)

A.S.Umar, V.E.Oberacker

Dynamical deformation effects in subbarrier fusion of 64Ni+132Sn

NUCLEAR REACTIONS 132Sn(64Ni, X), E(cm)=140-180 MeV; calculated internuclear potential, fusion σ, dynamical deformation effects.

doi: 10.1103/PhysRevC.74.061601
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2005BL12      Phys.Rev. C 71, 054321 (2005)

A.Blazkiewicz, V.E.Oberacker, A.S.Umar, M.Stoitsov

Coordinate space Hartree-Fock-Bogoliubov calculations for the zirconium isotope chain up to the two-neutron drip line

NUCLEAR STRUCTURE 102,104,106,108,110,112,114,116,118,120,122,124Zr; calculated binding energies, two-neutron separation energies, quadrupole moments, β2, radii, pairing energies. Hartree-Fock-Bogoliubov approach.

doi: 10.1103/PhysRevC.71.054321
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2005BL32      Eur.Phys.J. A 25, Supplement 1, 543 (2005)

A.Blazkiewicz, V.E.Oberacker, A.S.Umar

2-D lattice HFB calculations for neutron-rich zirconium isotopes

NUCLEAR STRUCTURE 102,104,106,108,110,112,114,116,118,120,122Zr; calculated two-neutron separation energies, quadrupole moments, radii. Hartree-Fock-Bogoliubov approach.

doi: 10.1140/epjad/i2005-06-100-7
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2005UM01      Phys.Rev. C 71, 034314 (2005)

A.S.Umar, V.E.Oberacker

Time-dependent response calculations of nuclear resonances

NUCLEAR STRUCTURE 16O, 32S, 40Ca; calculated giant resonance response functions, time-dependent features.

doi: 10.1103/PhysRevC.71.034314
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2005UM02      Eur.Phys.J. A 25, Supplement 1, 553 (2005)

A.S.Umar, V.E.Oberacker

TDHF studies with modern Skyrme forces

NUCLEAR REACTIONS 22Ne(16O, X), E=2.5 MeV/nucleon; calculate density distributions vs time; deduced orientation effects on fusion σ. Three-dimensional time-dependent Hartree-Fock approach, Skyrme forces.

doi: 10.1140/epjad/i2005-06-087-y
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2003OB06      Phys.Rev. C 68, 064302 (2003)

V.E.Oberacker, A.S.Umar, E.Teran, A.Blazkiewicz

Hartree-Fock-Bogoliubov calculations in coordinate space: Neutron-rich sulfur, zirconium, cerium, and samarium isotopes

NUCLEAR STRUCTURE 32,34,36,38,40,42,44,46,48,50,52S; calculated two-neutron separation energies, quadrupole moments, radii. 102,104Zr, 152Ce, 156Nd, 160Sm; calculated deformation parameters, radii. 158Sm; calculated ground-state binding energy, pairing energies, radii, density distributions. Hartree-Fock-Bogoliubov approach.

doi: 10.1103/PhysRevC.68.064302
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2003TE03      Phys.Rev. C 67, 064314 (2003)

E.Teran, V.E.Oberacker, A.S.Umar

Axially symmetric Hartree-Fock-Bogoliubov calculations for nuclei near the drip lines

NUCLEAR STRUCTURE 22O, 102Zr, 150Sn; calculated binding energies, pair gap energies, radii. Hartree-Fock-Bogoliubov approach, continuum coupling.

doi: 10.1103/PhysRevC.67.064314
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2002TE18      Acta Phys.Hung.N.S. 16, 437 (2002)

E.Teran, V.E.Oberacker, A.S.Umar

Theoretical Description of Hartree-Fock Calculations under Axial Symmetry: First Results on Tin Isotopes

NUCLEAR STRUCTURE 120,150Sn; calculated binding energies, pair gaps, deformation. Comparison with data.

doi: 10.1556/APH.16.2002.1-4.46
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2002TO06      Phys.Rev. C65, 037601 (2002)

M.Tohyama, A.S.Umar

Fusion Window Problem in Time-Dependent Hartree-Fock Theory Revisited

NUCLEAR REACTIONS 16O(16O, X), 22O(22O, X), E(cm) ≈ 30-80 MeV; calculated fusion threshold energies for various model assumptions. Time-dependent density-matrix theory.

doi: 10.1103/PhysRevC.65.037601
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2002TO20      Phys.Lett. 549B, 72 (2002)

M.Tohyama, A.S.Umar

Quadrupole Resonances in Unstable Oxygen Isotopes in Time-Dependent Density-Matrix Formalism

NUCLEAR STRUCTURE 22,24O; calculated quadrupole resonance strength distributions. Time-dependent density-matrix theory.

doi: 10.1016/S0370-2693(02)02885-X
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2001MA09      Phys.Rev. C63, 024902 (2001)

D.E.Malov, A.S.Umar, D.J.Ernst, D.J.Dean

Relativistic Heavy-Ion Collisions in the Dynamical String-Parton Model

NUCLEAR REACTIONS S, 197Au(p, X), E=200 GeV; S(S, X), E=200 GeV/nucleon; Pb(Pb, X), E=156 GeV/nucleon; calculated fragment rapidity distributions. Dynamical string-parton model, comparisons with data.

doi: 10.1103/PhysRevC.63.024902
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2000ER11      Acta Phys.Hung.N.S. 11, 239 (2000)

D.J.Ernst, D.E.Malov, A.S.Umar

Classical Strings and Relativistic Heavy-Ion Collisions

NUCLEAR REACTIONS 1H(p, X), E(cm)=30.4 GeV; S, Ar, Au(p, X), E=200 GeV/nucleon; S(S, X), E=200 GeV/nucleon; calculated multiplicity and rapidity distributions. Comparison with data. String-parton model.

1999GU10      Ann.Phys.(New York) 272, 7 (1999)

M.C.Guclu, J.Li, A.S.Umar, D.J.Ernst, M.R.Strayer

Electromagnetic Lepton-Pair Production in Relativistic Heavy-Ion Collisions

NUCLEAR REACTIONS Pb(Pb, X), E=160 GeV/nucleon; 197Au(S, X), E=200 GeV/nucleon; calculated lepton pair production σ(E); deduced impact parameter dependence. Two-photon external filed model, hybrid Monte Carlo technique. Comparison with data.

doi: 10.1006/aphy.1998.5876
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1999MA17      Phys.Rev. C59, 2289 (1999)

D.E.Malov, A.S.Umar, D.J.Ernst, D.J.Dean

Hadronic Structure Functions as Distributions of Classical Strings

doi: 10.1103/PhysRevC.59.2289
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1999MA74      Int.J.Mod.Phys. E8, 299 (1999)

D.E.Malov, A.S.Umar, D.J.Ernst, D.J.Dean

Particle Identification in the Dynamical String-Parton Model of Relativistic Heavy-Ion Collisions

doi: 10.1142/S0218301399000215
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1996CH31      Phys.Rep. 264, 107 (1996)

C.R.Chinn, A.S.Umar, M.Vallieres, M.R.Strayer

Mean Field Studies of Exotic Nuclei

NUCLEAR STRUCTURE 16O; calculated isoscalar axial quadrupole moment fluctuations vs time, isoscalar octupole moment response function. Mean field approach.

doi: 10.1016/0370-1573(95)00031-3
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1996NA03      Phys.Rev. C53, 740 (1996)

W.Nazarewicz, J.Dobaczewski, T.R.Werner, J.A.Maruhn, P.-G.Reinhard, K.Rutz, C.R.Chinn, A.S.Umar, M.R.Strayer

Structure of Proton Drip-Line Nuclei Around Doubly Magic 48Ni

NUCLEAR STRUCTURE 42,44Cr, 46,48Fe, 48,50Ni; calculated 2-proton separation energies, deformations, single-particle levels, diproton partial decay T1/2. Self-consistent, relativistic mean-field theories.

doi: 10.1103/PhysRevC.53.740
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1996WE02      Nucl.Phys. A597, 327 (1996)

T.R.Werner, J.A.Sheikh, M.Misu, W.Nazarewicz, J.Rikovska, K.Heeger, A.S.Umar, M.R.Strayer

Ground-State Properties of Exotic Si, S, Ar and Ca Isotopes

NUCLEAR STRUCTURE 28,30Si, 32,34,36S, 36,40Ar, 40,42,44,46,48Ca; calculated rms charge radius. Self-consistent.

doi: 10.1016/0375-9474(95)00476-9
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1995WE16      Nucl.Instrum.Methods Phys.Res. B99, 293 (1995)

J.C.Wells, V.E.Oberacker, M.R.Strayer, A.S.Umar

Lattice Calculation for Lepton Capture from Vacuum-Pair Production in Relativistic Heavy-Ion Collisions

NUCLEAR REACTIONS 197Au(197Au, X), E=2 GeV/nucleon; calculated muon-pair production associated K-shell capture probabilities, relativistic collisions. Lattice collocation techniques, time-dependent Dirac equation.

doi: 10.1016/0168-583X(94)00652-0
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1994WE11      Phys.Lett. 335B, 259 (1994)

T.R.Werner, J.A.Sheikh, W.Nazarewicz, M.R.Strayer, A.S.Umar, M.Misu

Shape Coexistence Around 4416S28: The deformed N = 28 region

NUCLEAR STRUCTURE 28,30,32,34,36,38,40,42,44,46,48,50,52,54S; analyzed two-neutron separation energies, masses, deformations, radii, single particle level energies; deduced stability features around 44S.

doi: 10.1016/0370-2693(94)90347-6
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1994WE16      Phys.Lett. 333B, 303 (1994)

T.R.Werner, J.A.Sheikh, W.Nazarewicz, M.R.Strayer, A.S.Umar, M.Misu

Shape Coexistence Around 4416S28: The deformed N = 28 Region

NUCLEAR STRUCTURE 28,30,32,34,36,38,40,42,44,46,48,50,52S; calculated two-neutron separation energies, quadrupole mass deformations, neutron distribution rms radii. Self-consistent mean field theory.

doi: 10.1016/0370-2693(94)90146-5
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1993DE48      Int.J.Mod.Phys. E2, 565 (1993)

D.J.Dean, A.S.Umar, M.R.Strayer

Dynamical Calculation of Central Energy Densities in Relativistic Heavy-Ion Collisions

NUCLEAR REACTIONS O(O, X), S(S, X), E=200 GeV/nucleon; calculated central meson density vs time, thermodynamic quantities vs scaled energy density, relativistic collisions. String-parton model.

doi: 10.1142/S0218301393000224
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1993OB02      Phys.Rev. C48, 1297 (1993)

V.E.Oberacker, A.S.Umar, J.C.Wells, C.Bottcher, M.R.Strayer, J.A.Maruhn

Muon-Induced Fission: A probe for nuclear dissipation and fission dynamics

NUCLEAR STRUCTURE 238U; calculated mesonic atom levels, Coulomb interaction potential; deduced muon induced fission features.

ATOMIC PHYSICS, Mesic-Atoms 238U; calculated mesonic atom levels, Coulomb interaction potential; deduced muon induced fission features.

doi: 10.1103/PhysRevC.48.1297
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1992OB03      Phys.Lett. 293B, 270 (1992)

V.E.Oberacker, A.S.Umar, J.C.Wells, M.R.Strayer, C.Bottcher

Study of Nuclear Dissipation via Muon-Induced Fission. A Relativistic Lattice Calculation

NUCLEAR REACTIONS 238U(μ-, F), E at rest; calculated muon-nucleus Coulomb interaction vs time during fission, muon to light fission fragment attachment probability vs dissipated energy. Relativistic lattice calculation.

doi: 10.1016/0370-2693(92)90882-5
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1991UM01      Phys.Rev. C44, 2512 (1991)

A.S.Umar, M.R.Strayer, J.-S.Wu, D.J.Dean, M.C.Guclu

Nuclear Hartree-Fock Calculations with Splines

NUCLEAR STRUCTURE 16O, 40Ca; calculated Hartree-Fock energies, n-, p-single particle energies. Spline collocation method.

doi: 10.1103/PhysRevC.44.2512
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1989DE27      Phys.Rev. C40, 1213 (1989)

D.J.Dean, A.S.Umar, M.R.Strayer

Velocity Dependence of Prompt, High-Energy Nucleon Emission

NUCLEAR REACTIONS 165Ho(58Ni, X), E=930 MeV; 93Nb(16O, X), E=204 MeV; calculated velocity, exit channel kinetic energy correlation for high energy nucleon emission. Time-dependent entrance channel formalism.

doi: 10.1103/PhysRevC.40.1213
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1987LE21      Phys.Lett. 196B, 419 (1987)

S.-J.Lee, A.S.Umar, K.T.R.Davies, M.R.Strayer, P.-G.Reinhard

Enhanced Dissipation in New Mean-Field Studies of Strongly Damped Collisions

NUCLEAR REACTIONS 139La(86Kr, X), E=610 MeV; calculated σ(fragment θ, E), rms radii, deflection function, kinetic energy. Time-dependent Hartree-Fock approximation.

doi: 10.1016/0370-2693(87)90793-3
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1986LE16      Phys.Rev.Lett. 57, 2916 (1986); Erratum Phys.Rev.Lett. 59, 1171 (1987)

S.-J.Lee, J.Fink, A.B.Balantekin, M.R.Strayer, A.S.Umar, P.-G.Reinhard, J.A.Maruhn, W.Greiner

Relativistic Hartree Calculations for Axially Deformed Nuclei

NUCLEAR STRUCTURE 12C, 16O, 20Ne, 24Mg, 40,48Ca; calculated binding energies, quadrupole moments. Relativistic Hartree calculations.

doi: 10.1103/PhysRevLett.57.2916
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1986UM01      Phys.Lett. 171B, 353 (1986)

A.S.Umar, M.R.Strayer

Nuclear Shape-Isomeric Vibrations

NUCLEAR STRUCTURE 24Mg; calculated isomer time evolution radius; deduced ion-ion collision correlated resonance source.

doi: 10.1016/0370-2693(86)91419-X
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1986UM02      Phys.Rev.Lett. 56, 2793 (1986)

A.S.Umar, M.R.Strayer, P.-G.Reinhard

Resolution of the Fusion Window Anomaly in Heavy-Ion Collisions

NUCLEAR REACTIONS 16O(16O, X), E(cm)=20, 34 MeV; calculated fusion σ. 16O(16O, 16O'), E=27-68 MeV; calculated inelastic thresholds; deduced spin-orbit interaction role. TDHF, Skyrme forces, spin-orbit interaction.

doi: 10.1103/PhysRevLett.56.2793
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1985UM01      Phys.Rev. C32, 172 (1985)

A.S.Umar, M.R.Strayer, R.Y.Cusson, P.-G.Reinhard, D.A.Bromley

Time-Dependent Hartree-Fock Calculations of 4He + 14C, 12C + 12C(0+), and 4He + 20Ne Molecular Formations

NUCLEAR REACTIONS 14C, 20Ne(α, α), 12C(12C, 12C), E ≈ Coulomb barrier; calculated composite system density contours, isoscalar quadrupole, octupole, isovector dipole moment frequency dependence; deduced dynamical degrees of freedom, associated classical frequencies. TDHF.

doi: 10.1103/PhysRevC.32.172
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1984ST02      Phys.Lett. 135B, 261 (1984)

M.R.Strayer, R.Y.Cusson, A.S.Umar, P.-G.Reinhard, D.A.Bromley, W.Greiner

Time-Dependent Hartree-Fock Picture of Nuclear Molecular Resonances

NUCLEAR STRUCTURE 18O; calculated isovector dipole, isocalar quadrupole, octupole molecular resonances. TDHF method.

doi: 10.1016/0370-2693(84)90387-3
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1984UM02      Phys.Lett. 140B, 290 (1984)

A.S.Umar, M.R.Strayer, D.J.Ernst

A Time-Dependent External-Field Model for Particle Emission in Heavy-Ion Reactions

NUCLEAR REACTIONS 93Nb(16O, nX), E=204 MeV; calculated inclusive nonequilibrium neutron emission probability vs t. Time-dependent external field model.

doi: 10.1016/0370-2693(84)90755-X
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1984UM05      Phys.Rev. C30, 1934 (1984)

A.S.Umar, M.R.Strayer, D.J.Ernst, K.R.Sandhya Devi

Mean-Field Theory of Prompt, High-Energy Nucleon Emission

NUCLEAR REACTIONS 93Nb(16O, X), E=204 MeV; calculated σ(θn, En) following fragment neutron emission. Time-dependent mean field theory.

doi: 10.1103/PhysRevC.30.1934
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