G.T. Emery

Indiana University Bloomington, Bloomington, IN, United States

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Publications (85)142.82 Total impact

  • Physics Today 01/2001; 54. · 6.76 Impact Factor
  • Nuclear Physics A - NUCL PHYS A. 01/1995; 588:729-766.
  • Source
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    ABSTRACT: A cross section enhancement, persisting to high momentum transfer, has been observed around 1ħω in excitation energy in spectra from inelastic proton-, alpha- and electron scattering on 90Zr, 116Sn, 196Pt and 208Pb. Data are presented for (p,p') at 201 MeV, (α, α') at 120 MeV and analyzed together with existing data obtained with 133.8 MeV polarized (,p') on 116Sn and electron-scattering data on 116Sn and 196Pt. Two different interpretations of the observed enhancement are discussed: that of the incoherent sum of all 1ħω cross section and alternatively the sum over the isoscalar normal modes of all multipolarities.
    Nuclear Physics A 01/1995; · 1.53 Impact Factor
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    ABSTRACT: The total cross section and angular distributions for the differential cross section and the analyzing power of the exclusive two-body pion production reaction 12C(p-->,pi0) 13Ng.s. have been measured at 147 MeV, very near the threshold energy of 145 MeV. Both the large forward-backward asymmetry in the angular distribution of the differential cross section and the large values observed for the analyzing powers indicate strong interference between the amplitude for s-wave pion emission and the amplitudes for p-wave pion emission. A phase-shift analysis performed on these new data yields significant p-wave strength at this low energy. The measurements for pi0 production from carbon are in agreement with results extracted from existing data for pi+ production from carbon, after corrections for isospin invariance and Coulomb effects. The reduced s-wave strength is found to have a simple power law dependence on the total number of nucleons in the final bound state.
    Physical Review C 01/1994; 48(6):2763-2771. · 3.72 Impact Factor
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    ABSTRACT: New cross section and analyzing power data for 88Sr(p,p') at Ep=200 MeV are reported and analyzed together with earlier cross section data. Neutron transition densities for low-lying normal-parity excitations were extracted using an empirical density-dependent effective interaction and an expansion of the radial density which permits analysis of uncertainties due to penetrability, distortion, incompleteness, statistics, and normalization. The densities were compared with shell-model calculations using effective operators based upon a density-dependent Hartree-Fock approximation. Good agreement between theory and experiment is obtained for the 2+1, 3-1, and 5-1 states, but the experimental neutron densities for the 2+2 and 7-1 states are considerably stronger than expected. Both proton and neutron transition densities for the 2+2 state have strong interior lobes, but the theory fails to reproduce the accompanying surface lobes.
    Physical Review C 06/1993; 47(5):2146-2158. · 3.72 Impact Factor
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    ABSTRACT: New cross section and analyzing power data for [sup 88]Sr([ital p],[ital p][prime]) at [ital E][sub [ital p]]=200 MeV are reported and analyzed together with earlier cross section data. Neutron transition densities for low-lying normal-parity excitations were extracted using an empirical density-dependent effective interaction and an expansion of the radial density which permits analysis of uncertainties due to penetrability, distortion, incompleteness, statistics, and normalization. The densities were compared with shell-model calculations using effective operators based upon a density-dependent Hartree-Fock approximation. Good agreement between theory and experiment is obtained for the 2[sub 1][sup +], 3[sub 1][sup [minus]], and 5[sub 1][sup [minus]] states, but the experimental neutron densities for the 2[sub 2][sup +] and 7[sub 1][sup [minus]] states are considerably stronger than expected. Both proton and neutron transition densities for the 2[sub 2][sup +] state have strong interior lobes, but the theory fails to reproduce the accompanying surface lobes.
    Physical Review C - PHYS REV C. 01/1993; 47(5):2146-2158.
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    ABSTRACT: Total cross sections and angular distributions for the differential cross section and analyzing power of the reaction 2H(p→,π0)3He have been measured at four energies very near threshold (0.1<Tπc.m.<2.7 MeV). The large asymmetries observed in the angular distributions of the differential cross section indicate strong constructive interference between the amplitudes for s-wave pion emission and the amplitudes for p-wave emission. A measure of the s-wave strength at zero energy is obtained and found to be consistent with the results from pionic atoms. The new data indicate that the excitation function for this reaction differs significantly from that of p+n→d+π0.
    Physical Review C 09/1992; 46(2):397-409. · 3.72 Impact Factor
  • Physical Review C 04/1992; 45(3):1017-1025. · 3.72 Impact Factor
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    ABSTRACT: The low-lying excited states of two rotational nuclei, 176Yb and 180Hf, have been investigated up to an excitation energy of 3.5 MeV by means of high-resolution inelastic scattering of 98.4-MeV polarized protons. The spins and excitation strengths of the observed levels have been deduced by comparing the measured cross sections and asymmetries with coupled-channel calculations. The deduced quadrupole, hexadecapole, and octupole strengths have been compared with the predictions of the interacting boson model in the sdg- and sdf-boson schemes.
    Physical Review C 03/1992; 45(3):1017-1025. · 3.72 Impact Factor
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    ABSTRACT: Cross section and analyzing power measurements for the scattering of 180 MeV protons are used to investigate the structure of 9Be. Data were collected for 24 states below 21 MeV of excitation. Detailed line-shape analysis was used to isolate several broad states. Most notably, the dependence of apparent peak position upon momentum transfer was used to separate the strong resonance listed as 6.76 MeV in standard compilations into two contributions identified as the 7/2- member of the ground-state rotational band, located at 6.38 MeV, and the 9/2+ weak-coupling state, located at 6.76 MeV. Calculations of proton scattering were made using a density-dependent effective interaction in the local density approximation. The quadrupole contribution to elastic scattering was included in distorted wave Born approximation and found to have an important effect upon the analyzing power. For states dominated by a single multipolarity, neutron transition densities were fitted to (p,p') data and compared with the corresponding proton transition densities fitted to (e,e') data. We find that excitation of the rotational states and the 9/2+ state are essentially isoscalar. Shell model calculations were performed in the full 0homega and 1homega model spaces. Suggested assignments for most states are made by comparisons of shell model calculations with data for both (p,p') and (e,e'). Similar calculations for analog states observed with the 9Be(p,n)9B reaction at 135 MeV support the proposed assignments. Finally, several relatively narrow states are observed between 18 and 21 MeV that are candidates for positive-parity states with T=3/2.
    Physical Review C 05/1991; 43(4):1758-1776. · 3.72 Impact Factor
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    ABSTRACT: Angular distributions of and Ay were measured for low-lying collective states, Jπ = 01+, 2+1, 2+2, 4+1, 4+2, 4+3 in 194,198pt using 135 MeV polarized protons. Coupled-channels analysis of the data indicates large E4 moments for the 4i (i = 1, 2, 3) states in both the isotopes. These data have been analyzed in the framework of the interacting boson model (IBM). Although the standard IBM-1 scheme with only s- and d-bosons can describe the E2 properties of both isotopes quite well, a more generalized version which also includes a g-boson is needed to correctly reproduce simultaneously both the E2 and E4 data. Another model using the “projected IBM-2” parameters gives similar results.
    Nuclear Physics A 11/1990; · 1.53 Impact Factor
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    ABSTRACT: Differential cross sections and analyzing powers for scattering of 180 MeV protons by ¹⁶O have been measured for all narrow states below 12.1 MeV of excitation. Medium modifications to the effective interaction for normal-parity isoscalar transitions were studied using transition densities determined by electron scattering to minimize nuclear structure uncertainties. An empirical effective interaction, guided by nuclear matter theory, was fitted to inelastic scattering data for six states simultaneously. Distorted waves were generated from self-consistent optical potentials computed from the same effective interaction. The isoscalar effective interaction determined by this procedure provides a good global fit to the inelastic scattering data and is consistent with elastic scattering data that were not included in the fit. The results are consistent with earlier results for 135 MeV and show that the effective interaction is suppressed at low density but is less density dependent than predicted by nuclear matter theory and the local density approximation. These comparisons suggest effects in finite nuclei beyond the local density approximation. Finally, we compare data for 0⁻ and 2⁻ states at both 135 and 180 MeV with representative calculations.
    Physical Review C 01/1990; 41(6):2504-2513. · 3.72 Impact Factor
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    ABSTRACT: Angular distributions of dsigma/dOmega and Ay were measured for low-lying collective states, Jpi = 01+, 2+1, 2+2, 4+1, 4+2, 4+3 in 194,198pt using 135 MeV polarized protons. Coupled-channels analysis of the data indicates large E4 moments for the 4i (i = 1, 2, 3) states in both the isotopes. These data have been analyzed in the framework of the interacting boson model (IBM). Although the standard IBM-1 scheme with only s- and d-bosons can describe the E2 properties of both isotopes quite well, a more generalized version which also includes a g-boson is needed to correctly reproduce simultaneously both the E2 and E4 data. Another model using the ``projected IBM-2'' parameters gives similar results. Current address: Lockheed Missiles and Space Company, P.O. Box 1103, Huntsville, AL 35807, USA.
    Nuclear Physics A - NUCL PHYS A. 01/1990; 518(3):536-560.
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    ABSTRACT: Angular distributions of dσ/dΩ and Ay for excitation of 01+, 21+, 22+, 41+, 42+ and 43+ states in 192Os by 134.5 MeV protons have been measured. Results for quadrupole transitions are in good agreement with previous results. For the L = 4 transitions to the first three 4+ states, quite large strengths are observed, much larger than expected from IBM1 calculations, particularly for the 43+ state.
    Nuclear Physics A. 09/1989; 501(3):546–556.
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    ABSTRACT: Differential cross sections and analyzing powers for scattering of 135-MeV protons by ¹⁶O have been measured for all narrow states below 12.1 MeV of excitation up to a momentum transfer of 3.2 fm⁻¹. Calculations that employ accurate transition densities fitted to electroexcitation data are used to study medium modifications to the two-nucleon effective interaction with little residual uncertainty from nuclear structure. Definitive evidence for strong density dependence in the isoscalar spin-independent central component of the two-nucleon effective interaction has been found. The differential cross sections show that as the density increases, the strength of the central interaction is suppressed at low momentum transfer and enhanced at high momentum transfer. The analyzing powers exhibit strong negative excursions near 2.5 fm⁻¹, which support enhanced repulsion at high density. The data are well described by the local-density approximation, which employs the nuclear-matter effective interaction appropriate to the density in the vicinity of the interacting nucleons. We find that the qualitative results are insensitive to ambiguities in the local-density prescription, the local-exchange approximation, and the choice of distorted waves. However, effective interactions based upon the Paris, Bonn, and Hamada-Johnston potentials do give substantially different results. Of these, the Paris-Hamburg effective interaction provides the best description of normal-parity isoscalar transitions. The analysis also supports a rearrangement contribution to the effective interaction for inelastic scattering.
    Physical Review C 05/1989; 39(4):1222-1241. · 3.72 Impact Factor
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    ABSTRACT: The inelastic scattering of 134 MeV protons to 6- states in 26Mg has been studied. Five 6- states were identified on the basis of their measured angular distributions and analyzing powers. By combining the results with those of companion electron scattering and (p,n) studies in 26Mg and proton studies in 28Si, it has been possible to extract isoscalar and isovector excitation amplitudes for each state.
    Physical Review C 04/1989; 39(3):749-760. · 3.72 Impact Factor
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    ABSTRACT: The inelastic scattering of 134 MeV protons to 6/sup -/ states in /sup 26/Mg has been studied. Five 6/sup -/ states were identified on the basis of their measured angular distributions and analyzing powers. By combining the results with those of companion electron scattering and (p,n) studies in /sup 26/Mg and proton studies in /sup 28/Si, it has been possible to extract isoscalar and isovector excitation amplitudes for each state.
    Phys. Rev. C; (United States). 02/1989; 39:3.
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    ABSTRACT: Angular distributions of dsigma/dOmega and Ay for excitation of 01+, 21+, 22+, 41+, 42+ and 43+ states in 192Os by 134.5 MeV protons have been measured. Results for quadrupole transitions are in good agreement with previous results. For the L = 4 transitions to the first three 4+ states, quite large strengths are observed, much larger than expected from IBM1 calculations, particularly for the 43+ state.
    Nuclear Physics A 01/1989; 501:546-556. · 1.53 Impact Factor
  • Article: 16O(p
    Physical Review C 02/1988; 37(1):215-223. · 3.72 Impact Factor
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    ABSTRACT: Differential cross sections and analyzing powers are presented for the /sup 16/O(p-arrow-right,..pi../sup +/)/sup 17/O* reaction at T/sub p/ = 250, 354, and 489 MeV and compared with preliminary 200 MeV data as well as previously published data taken at other energies above and below the ..delta../sub 1232/ resonance region. The differential cross sections for each final state exhibit an energy dependence similar to that of the pp..-->..d..pi../sup +/ reaction at equivalent center of mass energy and four-momentum transfer, as has been seen previously for (p,..pi../sup +/) reactions with other target nuclei. The shape of the analyzing power angular distributions varies with the /sup 17/O/sup */ nuclear final state. Some states exhibit broad similarities with that of the p-arrow-rightp..-->..d..pi../sup +/ reaction, while others are markedly different.
    Phys. Rev. C. 01/1988;