Publications [#313657] of Anton P. Tonchev

Papers Published
  1. Angell, CT; Karwowski, HJ; Kelley, JH; Tonchev, AP; Tornow, W, Photo-induced population of the h(11/2) isomeric states in (gamma, n) reactions, AIP Conference Proceedings, vol. 819 (2006), pp. 363-+ [doi] .

    The mechanism of excitation of isomeric h 11/2 states in nuclei around the closed shell at N=82 have been studied at the High-Intensity Gamma Source (HIγS). We have taken advantage of the monoenergetic (ΔE/E=1.5%) and pulsed γ-ray-beam from HIγS to perform in-beam spectroscopy measurements with an improved level of precision and sensitivity. The giant dipole resonances at 15 MeV in the N=82 target isotones 138 Ba, 140 Ce, and 142 Nd have been excited, and following neutron emission the γ-ray cascades leading to the isomeric h 11/2 state and the ground state were observed in the N=81 isotones. For all three nuclei a very similar de-excitation scheme was found. The only level observed from which the isomeric state was populated was found to be J π = 7/2 - . The ground state is principally populated from the states with spin and parities J π = 1/2 + , 5/2 + , and 7/2 + . The structure of the N=81 isotones and the role of the gateway states in isomer population will be discussed. The results of the measurements will be compared with statistical model calculations. © 2006 American Institute of Physics.