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Oslo Seminar, Oslo, 6 December, 2012

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1) M. Guttormsen et al., NIM A374 (1996) 371 2) M. Guttormsen et al., NIM A255 (1987) 518 3) A. Schiller et al., NIM A447 (2000) 498 Analysis of possible systematic errors of the Oslo method A.C. Larsen et al., Phys. Rev. C 83, (2011) Measure particle- coincidences Unfold spectra at each E 1) Apply the first-generation method 2) Ansatz: First-generation matrix P(E, E ) (E - E ) T (E ) 3) Normalization Examples of level density

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12 MeV d on 232 Th 24 MeV 3 He on 232 Th 12 MeV d on 232 Th 24 MeV 3 He on 232 Th 3 He –beam 3 He, ,d,t 5”x5” NaI M.Guttormsen, A.Bürger, T.E.Hansen, N.Lietaer, NIM A648(2011)168 ∆E-E Backwards: = 40 o – 54 o Backwards: = 40 o – 54 o Oslo Seminar, Oslo, 6 December, 2012

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(d,d’) 232 Th (d,p) 233 Th ( 3 He,t) 232 Pa ( 3 He,d) 233 Pa ( 3 He, ) 231 Th Oslo Seminar, Oslo, 6 December, 2012

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(d,p) The -energy distribution is the same if the decay starts at E after -emission or starts after the direct reaction into E. E

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Oslo Seminar, Oslo, 6 December, 2012

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spin 2-6 ħ ExEx 232 Th(d,p) 233 Th Oslo Seminar, Oslo, 6 December, 2012

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P(E x,E ) Level density Trans. coeff. (E f ) T(E ) P(E x,E ) Oslo Seminar, Oslo, 6 December, 2012

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Brink hypothesis Fermi’s golden rule

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Oslo Seminar, Oslo, 6 December, 2012

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Normalization Oslo Seminar, Oslo, 6 December, )A. Gilbert and A.G.W. Cameron, Can. J. Phys. 43, 1446 (1965) 2)T. von Egidy and D. Bucurescu, Phys. Rev. C 72, (2005), Phys. Rev. C 73, (E) (2006) 3)S. Goriely, HF+BCS Demetriou and Goriely, Nucl. Phys. A695 (2001) Sc Average level spacings D from neutron capture:

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Oslo Seminar, Oslo, 6 December, 2012

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231,232,233 Th and 232,233 Pa Inverse energy-weighted sum rule: K. Heyde, P. von Neumann-Cosel, A. Richter, Rev. Mod. Phys., 82, 2365 (2010) Oslo Seminar, Oslo, 6 December, 2012 M. Guttormsen et al., PRL 109, (2012)

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Thermal quasi-particles, the spectators of mid-shell nuclei Oslo Seminar, Oslo, 6 December, 2012

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Thermal quasi-particles create level density Oslo Seminar, Oslo, 6 December, 2012 Cooper pair Broken pair 1 level 25 levels

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A simple model for level density Oslo Seminar, Oslo, 6 December, Combining all possible proton and neutron configurations - Nilsson single-particle energy scheme - BCS quasi-particles j

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Nilsson level scheme Oslo Seminar, Oslo, 6 December, 2012 Model parameters: = = 0.32 = p 1n 1p 3n 1p 5n 1p 7n 3p 1n 3p 3n 3p 5n 5p 1n 5p 3n 7p 1n 20

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Level density and broken pairs Oslo Seminar, Oslo, 6 December, 2012 Level densities Number of broken pairs

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Parity asymmetry Oslo Seminar, Oslo, 6 December, 2012 U. Agvaanluvsan, G.E. Mitchell, J.F. Shriner Jr., Phys. Rev. C 67, (2003)

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Titanium and tin Oslo Seminar, Oslo, 6 December, Ti

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Summary Oslo Seminar, Oslo, 6 December, 2012 Simultaneous extraction of level density and -strength function Examples from A = 40 – 230 Number of thermal quasi-particles determines number of levels Constant temperature level density Fluctuations for lighter even-even nuclei

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Oslo Seminar, Oslo, 6 December, 2012

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