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

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

doi:10.1103/physrevc.70.054611

arXiv · nucl-ex/0412029

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

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

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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$^\primeγ$)$^{171}$Yb and $^{171}$Yb($^3$He,$αγ$)$^{170}$Yb reactions. New data on $^{171}$Yb are compared to a previous measurement for $^{171}$Yb from the $^{172}$Yb($^3$He,$αγ$)$^{171}$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,$α$) reaction appear to be split into two components for both of which a complete set of resonance parameters are obtained.

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U. Agvaanluvsan, A. Schiller, J. A. Becker, L. A. Bernstein, P. E. Garrett, M. Guttormsen, G. E. Mitchell, J. Rekstad, S. Siem, A. Voinov, W. Younes. 2004-12-13. Level densities and $γ$-ray strength functions in $^{170,171,172}$Yb. https://doi.org/10.1103/physrevc.70.054611

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