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Title: Photon strength and the low-energy enhancement

Several measurements in medium mass nuclei have reported a low-energy enhancement in the photon strength function. Although, much effort has been invested in unraveling the mysteries of this effect, its physical origin is still not conclusively understood. Here, a completely model-independent experimental approach to investigate the existence of this enhancement is presented. The experiment was designed to study statistical feeding from the quasi-continuum (below the neutron separation energy) to individual low-lying discrete levels in {sup 95}Mo produced in the (d, p) reaction. A key aspect to successfully study gamma decay from the region of high-level density is the detection and extraction of correlated particle-gamma-gamma events which was accomplished using an array of Clover HPGe detectors and large area annular silicon detectors. The entrance channel excitation energy into the residual nucleus produced in the reaction was inferred from the detected proton energies in the silicon detectors. Gating on gamma-transitions originating from low-lying discrete levels specifies the state fed by statistical gamma-rays. Any particle-gamma-gamma event in combination with specific energy sum requirements ensures a clean and unambiguous determination of the initial and final state of the observed gamma rays. With these requirements the statistical feeding to individual discrete levels is extracted onmore » an event-by-event basis. The results are presented and compared to {sup 95}Mo photon strength function data measured at the University of Oslo.« less
Authors:
 [1] ; ; ; ; ; ;  [2] ;  [3] ;  [4] ; ; ; ; ; ; ; ;  [5] ;  [6]
  1. iThemba LABS, P.O. Box 722, Somerset West 7129 (South Africa)
  2. Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
  3. Faculty of Mathematics and Physics, Charles University, V Holešovickách 2, Prague 8 (Czech Republic)
  4. Department of Physics, University of Richmond, Virginia 23173 (United States)
  5. Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  6. Department of Nuclear Engineering, University of California, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
22308431
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1609; Journal Issue: 1; Conference: FIG12: International conference on frontiers in gamma-ray spectroscopy 2012, New Delhi (India), 5-7 Mar 2012; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; EXCITATION; GAMMA DECAY; GAMMA RADIATION; HIGH-PURITY GE DETECTORS; MOLYBDENUM 95; NEUTRON SEPARATION ENERGY; PHOTONS; SI SEMICONDUCTOR DETECTORS; STRENGTH FUNCTIONS