Radiative Strength Functions in 172Yb below 8 Me V

Schiller, A ; Becker, J A ; Bernstein, L A ; Garrett, P E ; Hill, T S ; McNabb, D P ; Younes, W ; Tavukcu, E ; Vomov, A ; Guttormsen, M ; Rekstad, J ; Siem, S

Lawrence Livermore National Laboratory

关键词: Clover;    Rare Earth Nuclei;    Spectra;    71 Classical And Quantum Mechanics, General Physics;    Resonance;   

DOI  :  10.2172/15002354
RP-ID  :  UCRL-ID-147425
RP-ID  :  W-7405-ENG-48
RP-ID  :  15002354

美国|英语

来源: UNT Digital Library

【 摘 要 】

We have measured prompt {gamma} rays after thermal and resonant neutron capture in {sup 171}Yb. The {gamma} rays were measured with three high resolution ({approx}3 keV) and high efficiency (two {approx}80% Ge(HP) and one {approx}200% segmented Clover) detectors. We have obtained singles and two-fold coincidence spectra as function of neutron energy using the time-of-flight technique. Two-fold coincidences where the summed energy adds up to the neutron binding energy B{sub n} or to B{sub n} minus the energy of the first excited stated ({approx}79 keV) will be used to determine the multipolarity of the pygmy resonance in {sup 172}Yb. This pygmy resonance is a resonant structure in the radiative strength function around {approx}3 MeV in deformed rare earth nuclei [1]. The following goals were met: (1) We have shown the feasibility of prompt, high-resolution {gamma} spectroscopy at FP14 after thermal as well as resonant neutron capture. (2) Online analysis shows that sufficient statistics ({approx}7000 counts) are expected in each of the two relevant peaks in the summed-energy spectrum. Analysis of the experiment is in progress. It still remains to show that the multipolarity of the pygmy resonance can be determined experimentally from two-step cascade intensities.