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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.

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Presentation on theme: "Presentation of the PhD thesis “Statistical properties in the quasi- continuum of atomic nuclei” Ann-Cecilie Larsen May 20, 2008 Ann-Cecilie Larsen May."— Presentation transcript:

1 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

2 Ann-Cecilie Larsen2 The atomic nucleus

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

4 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 

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

6 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?

7 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

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

9 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

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

11 May 20, 2008Ann-Cecilie Larsen11 Experimental level densities

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

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

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

15 May 20, 2008Ann-Cecilie Larsen15 Microcanonical entropy

16 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

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

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

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

20 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

21 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.

22 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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