Anton P Tonchev

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The value of an isomeric ratio (IR) in N=81 isotones (137Ba, 139Ce, 141Nd and 143Sm) is studied by means of the (γ, n) reaction. This quantity measures a probability to populate the isomeric state in respect to the ground state population. In (γ, n) reactions, the giant dipole resonance (GDR) is excited and after its decay by a neutron emission, the nucleus(More)
High-sensitivity studies of E1 and M1 transitions observed in the reaction 138Ba(gamma,gamma{'}) at energies below the one-neutron separation energy have been performed using the nearly monoenergetic and 100% linearly polarized photon beams of the HIgammaS facility. The electric dipole character of the so-called "pygmy" dipole resonance was experimentally(More)
The electromagnetic dipole strength below the neutron-separation energy has been studied for the xenon isotopes with mass numbers A=124, 128, 132, and 134 in nuclear resonance fluorescence experiments using the γELBE bremsstrahlung facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIγS facility at Triangle Universities Nuclear Laboratory Durham. The(More)
The value of an isomeric ratio (IR) in N=81 isotones (137Ba, 139Ce, 141Nd and 143Sm) is studied by means of the (γ, n) reaction. This quantity measures a probability to populate the isomeric state in respect to the ground state population. In (γ, n) reactions, the giant dipole resonance (GDR) is excited and after its decay by a neutron emission, the nucleus(More)
The M1 excitations in the nuclide 90Zr have been studied in a photon-scattering experiment with monoenergetic and linearly polarized beams from 7 to 11 MeV. More than 40 J(π)=1+ states have been identified from observed ground-state transitions, revealing the fine structure of the giant M1 resonance with a centroid energy of 9 MeV and a sum strength of(More)
The two-body photodisintegration cross section of (4)He into a proton and triton was measured with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. High-pressure (4)He-Xe gas scintillators of various (4)He/Xe ratios served as targets and detectors. Pure Xe gas scintillators were used for background studies. A NaI detector together(More)
S. O. Nelson, M. W. Ahmed, B. A. Perdue, K. Sabourov, A. L. Sabourov, A. P. Tonchev, R. M. Prior, M. Spraker, and H. R. Weller Department of Physics, Duke University, Durham, North Carolina 27708, USA Triangle Universities Nuclear Laboratory, Duke Station, Durham, North Carolina 27708, USA Department of Physics, North Georgia College and State University,(More)
The quality and intensity of gamma rays at the High Intensity gamma-ray Source are shown to make nuclear resonance fluorescence studies possible at a new level of precision and efficiency. First experiments have been carried out using an intense (10(7) gamma/s) beam of 100% linearly polarized, nearly monoenergetic, gamma rays on the semimagic nucleus(More)
The objective of this paper is threefold: (1) to establish sensitivity of XRQA and EBT radiochromic films to fast neutron exposure; (2) to develop a film response to radiation dose calibration curve and (3) to investigate a two-dimensional (2D) film dosimetry technique for use in establishing an experimental setup for a radiobiological irradiation of mice(More)
Previous work at TUNL [Lay96] on the 6Li(p, )7Be reaction at 80 keV indicated that the reaction appears to proceed almost entirely by s-wave capture in contrast to the 7Li(p, )8Be reaction. The S factor for this latter reaction (EB = 17.25 MeV) was found to have a large negative slope as a function of energy at low energies [Spr00]. This slope was(More)