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Presentation of the PhD thesis “Statistical properties in the quasi- continuum of atomic nuclei” Ann-Cecilie Larsen May 20, 2008 Ann-Cecilie Larsen May 20, 2008

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Ann-Cecilie Larsen2 The atomic nucleus

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May 20, 2008Ann-Cecilie Larsen3 Quantum energy levels Nuclear level density = number of energy levels within one energy unit

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May 20, 2008Ann-Cecilie Larsen4 Decay probability Transition between quantum levels Fermi’s golden rule: Gamma-ray transmission coefficients and strength functions Transition between quantum levels Fermi’s golden rule: Gamma-ray transmission coefficients and strength functions Giant dipole resonance, 98 Mo i f

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May 20, 2008Ann-Cecilie Larsen5 Applications Nucleosynthesis in supernovae Transmutation of nuclear waste Nucleosynthesis in supernovae Transmutation of nuclear waste

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May 20, 2008Ann-Cecilie Larsen6 Motivation Level density and gamma-ray strength function in medium-mass nuclei: 44,45 Sc, 50,51 V, Mo Shell effects? Decay probability in the quasi-continuum? Level density and gamma-ray strength function in medium-mass nuclei: 44,45 Sc, 50,51 V, Mo Shell effects? Decay probability in the quasi-continuum?

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May 20, 2008Ann-Cecilie Larsen7 The Oslo Cyclotron Laboratory Reactions: inelastic scattering ( 3 He, 3 He’ ), and pick-up ( 3 He, ) Low spin and high intrinsic excitation energy CACTUS: 28 5”x5” NaI (~15% eff.) Eight E-E Si particle telescopes Reactions: inelastic scattering ( 3 He, 3 He’ ), and pick-up ( 3 He, ) Low spin and high intrinsic excitation energy CACTUS: 28 5”x5” NaI (~15% eff.) Eight E-E Si particle telescopes

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May 20, 2008Ann-Cecilie Larsen8 Particle-gamma coincidences Si E-E telescope 45 o NaI(Tl) 3 He Target nucleus

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May 20, 2008Ann-Cecilie Larsen9 The Oslo method in a Unfold -ray spectra Apply first-generation subtraction method Ansatz: decay probability (E x -E ) T (E ) Unfold -ray spectra Apply first-generation subtraction method Ansatz: decay probability (E x -E ) T (E ) 44 Sc

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May 20, 2008Ann-Cecilie Larsen10 Quality of the extraction, 44 Sc

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May 20, 2008Ann-Cecilie Larsen11 Experimental level densities

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May 20, 2008Ann-Cecilie Larsen12 Shell effects in the Mo isotopes Back-shifted Fermi gas : Calc. from neutron res. data

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May 20, 2008Ann-Cecilie Larsen13 Comparison with theory, 51 V Fermi gas?

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May 20, 2008Ann-Cecilie Larsen14 Thermodynamics Microcanonical vs. canonical ensemble

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May 20, 2008Ann-Cecilie Larsen15 Microcanonical entropy

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May 20, 2008Ann-Cecilie Larsen16 Combinatorial model Combining all possible proton and neutron configurations Nilsson energy scheme BCS quasiparticles Combining all possible proton and neutron configurations Nilsson energy scheme BCS quasiparticles J

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May 20, 2008Ann-Cecilie Larsen17 Calculated level densities, average number of broken pairs

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May 20, 2008Ann-Cecilie Larsen18 Parity asymmetry Defining the parity asymmetry:

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May 20, 2008Ann-Cecilie Larsen19 Experimental gamma-ray strength functions

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May 20, 2008Ann-Cecilie Larsen20 Comparison with theory Anomalous strength functions? T XL (E ) = 2 E 2L+1 f XL f XL (E ) = E -(2L+1) XL (E ) /D Assuming only dipole radiation: f (E ) T (E ) / 2 E 3

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May 20, 2008Ann-Cecilie Larsen21 Papers included in the thesis PublicationMy contribution Radiative strength functions in Mo [Phys. Rev. C 71, (2005)] Discussions of the results, suggestions to and proof-reading of the manuscript. Level densities and thermodynamic quantities of heated Mo isotopes [Phys. Rev. C 73, (2006)] Discussions of the results (mainly level densities and microcanonical results), suggestions to and proof-reading of the manuscript. Microcanonical entropies and radiative strength functions of 50,51 V [Phys. Rev. C 73, (2006)] Main author. Performed the data analysis and calculations. Wrote the manuscript. Nuclear level densities and gamma-ray strength functions in 44,45 Sc [Phys. Rev. C 76, (2007)] Main author. Performed the data analysis and calculations. Wrote the manuscript. Level densities of 44 Sc and 47 Ti from different experimental techniques [Phys. Rev. C 77, (2008)] Provided data and info for the OCL exp. ( 44 Sc). Suggestions to and proof-reading of the manuscript. Participated in the Ohio exp.

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May 20, 2008Ann-Cecilie Larsen22 Highlights The Oslo method works well for medium- mass nuclei Pronounced shell effects Single quasi-particle entropy constant, but vanish near shell closures Enhancement of low-energy gamma decay probability established for all nuclei studied The Oslo method works well for medium- mass nuclei Pronounced shell effects Single quasi-particle entropy constant, but vanish near shell closures Enhancement of low-energy gamma decay probability established for all nuclei studied

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