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Level densities and $\gamma$-ray strength functions in $^{170,171,172}$Yb

By U Agvaanluvsan, A Schiller, J A Becker, L A Bernstein, P E Garrett, M Guttormsen, G E Mitchell, J Rekstad, S Siem, A Voinov and W Younes

Abstract

Level densities and radiative strength functions in $^{171}$Yb and $^{170}$Yb nuclei have been measured using the $^{171}$Yb($^3$He,$^3$He$^\prime\gamma$)$^{171}$Yb and $^{171}$Yb($^3$He,$\alpha\gamma$)$^{170}$Yb reactions. New data on $^{171}$Yb are compared to a previous measurement for $^{171}$Yb from the $^{172}$Yb($^3$He,$\alpha\gamma$)$^{171}$Yb reaction. Systematics of level densities and radiative strength functions in $^{170,171,172}$Yb are established. The entropy excess in $^{171}$Yb relative to the even-even nuclei $^{170,172}$Yb due to the unpaired neutron quasiparticle is found to be approximately 2$k_B$. Results for the radiative strength function from the two reactions lead to consistent parameters characterizing the ``pygmy'' resonances. Pygmy resonances in the $^{170,172}$Yb populated by the ($^3$He,$\alpha$) reaction appear to be split into two components for both of which a complete set of resonance parameters are obtained

Topics: Nuclear Physics
Year: 2004
DOI identifier: 10.2172/15014599
OAI identifier: oai:cds.cern.ch:810683
Provided by: CERN Document Server
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