Browsing by Author "Xu, HM"

Now showing 1 - 7 of 7
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    Asymptotic normalization coefficients for B-10->Be-9+p
    (American Physical Society, 1997) Mukhamedzhanov, AM; Clark, HL; Gagliardi, Carl A.; Lui, YW; Trache, L.; Tribble, Robert E.; Xu, HM; Zhou, XG; Burjan, V.; Cejpek, J.; Kroha, V.; Carstoiu, F.
    The differential cross sections for the reactions Be-9(B-10, B-10)Be-9 and Be-9(B-10,Be-9)B-10 have been measured at an incident energy of 100 MeV. The elastic scattering data have been used to determine the optical model parameters for the Be-9+B-10 system at this energy. These parameters are then used in distorted-wave Born approximation (DWBA) calculations to predict the cross sections of the Be-9(B-10,Be-9)B-10 proton exchange reaction, populating the ground and low-lying states in B-10. By normalizing the theoretical DWBA proton exchange cross sections to the experimental ones, the asymptotic normalization coefficients (ANC's), defining the normalization of the tail of the B-10 bound state wave functions in the two-particle channel Be-9+p, have been found. The ANC for the virtual decay B-10(g.s.)-->Be-9+p will be used in an analysis of the B-10(Be-7,B-8)Be-9 reaction to extract the ANC's for B-8-->Be-7+p. These ANC's determine the normalization of the Be-7(p,gamma)B-8 radiative capture cross section at very low energies, which is crucially important for nuclear astrophysics.
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    (D,he-2) Reactions at E(d)=125.2 Mev
    (American Physical Society, 1995) Xu, HM; Ajupova, G. K.; Betker, A. C.; Gagliardi, Carl A.; Kokenge, B.; Lui, YW; Zaruba, A. F.
    We have measured cross sections for (d, He-2) induced reactions on the p-shell nuclei Li-6, C-12, and C-13 and the sd-shell nucleus Mg-24 at an energy of E(d)=125.2 MeV. The measured excitation energy spectra are very similar to those from (p, n), (n, p), and (d, He-Z) reactions at higher energies. The measured 0 degrees (d, He-2) cross sections show a remarkably well-defined linear relation with
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    Deuteron Elastic-Scattering at 110 and 120 Mev
    (American Physical Society, 1993) Betker, A. C.; Gagliardi, Carl A.; Semon, D. R.; Tribble, Robert E.; Xu, HM; Zaruba, A. F.
    Deuteron elastic scattering cross sections have been measured at 110 and 120 MeV on C, Ni-58, and Pb-208. Optical model potentials have been extracted and compared to deuteron global optical model potentials.
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    Formation and Decay of Toroidal and Bubble Nuclei and the Nuclear-Equation of State
    (American Physical Society, 1993) Xu, HM; Natowitz, J. B.; Gagliardi, Carl A.; Tribble, Robert E.; Wong, C. Y.; Lynch, W. G.
    Multifragmentation, following the formation of toroidal and bubble nuclei, is observed with an improved Boltzmann-Uehling-Uhlenbeck model for central Mo-92 + Mo-92 collisions. With a stiff equation of state, simultaneous explosion into several nearly equal fragments in a ringlike manner occurs due to the formation of metastable toroidal nuclei. In contrast, with a soft equation of state, simultaneous explosion into several nearly equal fragments in a volumelike manner occurs due to the formation of metastable bubble nuclei. Experimental signatures for the formation of these exotic shapes are discussed.
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    Fragmentation Barriers of Toroidal and Bubble Nuclei
    (American Physical Society, 1994) Xu, HM; Gagliardi, Carl A.; Tribble, Robert E.; Wong, C. Y.
    With an improved Boltzmann-Uehling-Uhlenbeck model, the deformation energy surfaces in reactions leading to the formation of toroidal and bubble nuclei are examined for central Mo-92+Mo-92 collisions. We found that the potential maximum, or the fragmentation barrier, occurs at times close to the times when these exotic shapes are formed. However, due to the dynamics of large amplitude compression and expansion, the fragmentation barriers are significantly higher than those estimated from the liquid-drop models.
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    Gamow-Teller strength of Mg-26
    (American Physical Society, 1996) Xu, HM; Gagliardi, Carl A.; Ajupova, G. K.; Kokenge, B.; Lui, YW.
    We have measured cross sections for (d,He-2)-induced reactions on Mg-26 at an energy of E(d)=125.2 MeV. The measured Gamow-Teller strength is significantly smaller than that inferred from (p,n) reactions. We demonstrate that beta(+) Gamow-Teller strengths for T-0 + 1 states deduced from (p,n) reactions may have significant systematic uncertainties due to ambiguities in the large backgrounds that must be subtracted.
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    l-forbidden Gamow-Teller beta decay of Cu-57
    (American Physical Society, 1996) Semon, D. R.; Allen, MC; Dejbakhsh, H.; Gagliardi, Carl A.; Hale, SE; Jiang, J.; Trache, L.; Tribble, Robert E.; Yennello, SJ; Xu, HM; Zhou, XG; Brown, BA.
    Absolute branching ratios for the beta decay of Cu-57 to excited states up to 3.3 MeV in Ni-57 have been determined, including the rho-forbidden Gamow-Teller transition to the first excited state in Ni-57. Four transitions to excited states at 0.768, 1.113, 2.443, and 3.007 MeV are observed in addition to the superallowed decay to the ground state of Ni-57. The, measured branching ratio to the ground state is 89.9 +/- 0.8% and the branching ratios to the four excited states are 0.94 +/- 0.09%, 8.6 +/- 0.6%, 0.17 +/- 0.03%, and 0.35 +/- 0.04%, respectively. In addition we have measured the Cu-57 half-life and find it to be 196.3 +/- 0.7 ms, which is in good agreement with the most recent measurement. B(GT) values have been extracted from the new results and are compared to shell model calculations.