40 research outputs found
Projectile deformation effects on single-nucleon removal reactions
Get PDFWe discuss intermediate-energy single-nucleon removal reactions from deformed projectile nuclei. The removed nucleon is assumed to originate from a given Nilsson model single-particle state and the inclusive cross sections, to all rotational states of the residual nucleus, are calculated. We investigate the sensitivity of both the stripping cross sections and their momentum distributions to the assumed size of the model space in the Nilsson model calculations and to the shape of the projectile and residue. We show that the cross sections for small deformations follow the decomposition of the Nilsson state in a spherical basis. In the case of large and prolate projectile deformations the removal cross sections from prolate-like Nilsson states, having large values for the asymptotic quantum number n z, are reduced. For oblate-like Nilsson states, with small n z, the removal cross sections are increased. Whatever the deformation, the residue momentum distributions are found to remain robustly characteristic of the orbital angular momentum decomposition of the initial state of the nucleon in the projectile. � 2012 American Physical Society
Two-proton removal from 44 S and the structure of 42 Si
Get PDFNewly published 42Si ?-ray spectra and a final-state-inclusive 42Si production cross section value, obtained in a higher-statistics intermediate-energy two-proton removal experiment from 44S, are considered in terms of the final-state-exclusive cross sections computed using proposed shell-model effective interactions for nuclei near N=28. Specifically, we give cross section predictions when using the two nucleon amplitudes of the two-proton overlaps 42Si(J?)| computed using the newly proposed sdpf-mu shell-model Hamiltonian. We show that these partial cross sections or their longitudinal momentum distributions should enable a less-tentative interpretation of the measured gamma-ray spectra and provide a more quantitative assessment of proposed shell-model Hamiltonians in this interesting and challenging region of the chart of nuclides. � 2013 American Physical Society
Four-body continuum-discretized coupled-channels calculations: Application to 6He+64Zn at 13.6 MeV
Get PDFThe recently developed four-body continuum-discretized coupled-channels (CDCC) method, making use of the binning procedure [1], is applied to the reaction 6He+64Zn at 13.6 MeV (around the Coulomb barrier). Excellent agreement with available elastic data [2] is found.Dirección General de Investigación CientÃfica y Técnica FIS 2008-04189, FPA 2006- 13807-C02-01U.S. Department of Energy DE-AC52-07NA27344U.K. STFC EP/D00362
Correlations in Intermediate Energy Two-Proton Removal Reactions
Get PDFWe report final-state-exclusive measurements of the light charged fragments in coincidence with Ne26 residual nuclei following the direct two-proton removal from a neutron-rich Mg28 secondary beam. A Dalitz-plot analysis and comparisons with simulations show that a majority of the triple-coincidence events with two protons display phase-space correlations consistent with the (two-body) kinematics of a spatially correlated pair-removal mechanism. The fraction of such correlated events, 56(12)%, is consistent with the fraction of the calculated cross section, 64%, arising from spin S=0 two-proton configurations in the entrance-channel (shell-model) Mg28 ground state wave function. This result promises access to an additional and more specific probe of the spin and spatial correlations of valence nucleon pairs in exotic nuclei produced as fast secondary beams. � 2012 American Physical Society
Isospin symmetry at high spin studied via nucleon knockout from isomeric states
Get PDFOne-neutron knockout reactions have been performed on a beam of radioactive 53Co in a high-spin isomeric state. The analysis is shown to yield highly-selective population of high-spin states in an exotic nucleus with a significant cross section, and hence represents a technique that is applicable to the planned new generation of fragmentation-based radioactive beam facilities. Additionally, the relative cross sections among the excited states can be predicted to a high level of accuracy when reliable shell-model input is available. The work has resulted in a new level scheme, up to the 11+ band-termination state, of the proton-rich nucleus 52Co (Z = 27, N = 25). This has in turn enabled a study of mirror energy differences in the A = 52 odd-odd mirror nuclei, interpreted in terms of isospin-non-conserving (INC) forces in nuclei. The analysis demonstrates the importance of using a full set of J-dependent INC terms to explain the experimental observations
Fragmentation of single-particle strength around the doubly-magic nucleus 132Sn and the position of the 0f5/2 proton-hole state in 131In
Get PDFSpectroscopic factors of neutron-hole and proton-hole states in 131Sn and 131In, respectively, were
measured using one-nucleon removal reactions from doubly magic 132Sn at relativistic energies. For 131In, a
2910(50)-keV γ ray was observed for the first time and tentatively assigned to a decay from a 5=2− state
at 3275(50) keV to the known 1=2− level at 365 keV. The spectroscopic factors determined for this new
excited state and three other single-hole states provide first evidence for a strong fragmentation of singlehole strength in 131Sn and 131In. The experimental results are compared to theoretical calculations based on
the relativistic particle-vibration couplin
Reaction spectroscopy at fragmentation beam energies - recent advances in studies of two-nucleon removal
No full textFinal-state-exclusive two-nucleon removal reaction data from fast fragmentation beams can provide a demanding test of the microscopic two-nucleon transition densities calculated from large-basis shell model wave functions. The sensitivity of measured partial cross sections to pairing and other correlations is discussed. It is also suggested that the widths of the momentum distributions of these partial cross sections will exhibit a strong dependence on the final-state of the residue and the projectile structure
A Study of Polarization Effects in Subcoulomb (d,p) Reactions.
No full textThe accuracy of sub-coulomb (d,p) reaction tensor analysing powers, calculated using the conventional DWBA theory, is investigated. Two outstanding uncertainties in the DWBA method, relating to a) breakup of the deuteron in the coulomb field of the target nucleus, and b) the presence of T R tensor interactions in the deuteron target system, are studied quantitatively. Particular emphasis is placed upon the reaction 208Pb (d,p) 209Pb, at Ed = 9 MeV and Ed = 7 MeV, and its applicability to the measurement of the parameter of Johnson and Santos. Coulomb break up is treated in dipole approximation using perturbation theory and an adiabatic prescription. Special attention is paid to the use of a realistic state dependent interaction in the P-wave n-p continuum. Coulomb and strong tensor T[R] terms, obtained from both elastic scattering and break up models, are discussed and are included through a generalization of the conventional, Local Energy Approximation, DWBA stripping formalism. The resulting coupled differential equations are solved numerically. Results of calculations show that both effects studied must be accounted for in any analysis of precision experimental data at 9 MeV and/ or 7 MeV. Theoretical uncertainties in the strong interaction contribution to the T R potential, to which calculations at 9 MeV are sensitive, are found to be unimportant at an energy of 7 MeV. The effects of singlet ([1]S[0]) breakup of the deuteron are also shown to be completely negligible
A Study of Polarization Effects in Subcoulomb (d,p) Reactions.
No full textThe accuracy of sub-coulomb (d,p) reaction tensor analysing powers, calculated using the conventional DWBA theory, is investigated. Two outstanding uncertainties in the DWBA method, relating to a) breakup of the deuteron in the coulomb field of the target nucleus, and b) the presence of T R tensor interactions in the deuteron target system, are studied quantitatively. Particular emphasis is placed upon the reaction 208Pb (d,p) 209Pb, at Ed = 9 MeV and Ed = 7 MeV, and its applicability to the measurement of the parameter of Johnson and Santos. Coulomb break up is treated in dipole approximation using perturbation theory and an adiabatic prescription. Special attention is paid to the use of a realistic state dependent interaction in the P-wave n-p continuum. Coulomb and strong tensor T[R] terms, obtained from both elastic scattering and break up models, are discussed and are included through a generalization of the conventional, Local Energy Approximation, DWBA stripping formalism. The resulting coupled differential equations are solved numerically. Results of calculations show that both effects studied must be accounted for in any analysis of precision experimental data at 9 MeV and/ or 7 MeV. Theoretical uncertainties in the strong interaction contribution to the T R potential, to which calculations at 9 MeV are sensitive, are found to be unimportant at an energy of 7 MeV. The effects of singlet ([1]S[0]) breakup of the deuteron are also shown to be completely negligible
