1 / 28

Ann-Cecilie Larsen Workshop on Level Density and Gamma Strength in Continuum Oslo, May 21-24, 2007

Experimental level densities and  -ray strength functions in the f 7/2 nuclei 44,45 Sc and 50,51 V. Ann-Cecilie Larsen Workshop on Level Density and Gamma Strength in Continuum Oslo, May 21-24, 2007. DEPARTMENT OF PHYSICS UNIVERSITY OF OSLO. Overview. Motivation - why study Sc and V?

liluye
Télécharger la présentation

Ann-Cecilie Larsen Workshop on Level Density and Gamma Strength in Continuum Oslo, May 21-24, 2007

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Experimental level densities and -ray strength functions in the f7/2 nuclei 44,45Sc and 50,51V Ann-Cecilie Larsen Workshop on Level Density and Gamma Strength in Continuum Oslo, May 21-24, 2007 DEPARTMENT OF PHYSICS UNIVERSITY OF OSLO

  2. Overview • Motivation - why study Sc and V? • Some experimental details • The Oslo method • Level densities • Gamma-ray strength functions • Summary

  3. Motivation • Nuclei with A~40-50 • Shell effects, Z=20, N=28 shell gap • Upbend structure in strength functions? (previously seen in 56,57Fe, 93-98Mo)

  4. Where are we? (I) 44,45Sc,  44Sc,  45Sc,  f5/2 f5/2 f5/2 p3/2 p3/2 p3/2 f7/2 f7/2 f7/2 d3/2 d3/2 d3/2

  5. 50,51V,  50V,  51V,  f5/2 f5/2 f5/2 p3/2 p3/2 p3/2 f7/2 f7/2 f7/2 d3/2 d3/2 d3/2 Where are we? (II)

  6. Experimental details (I) 3He beam, 30 MeV on 51V and 38 MeV on 45Sc. Reactions: Inelastic scattering(3He,3He’) Pick-up (3He,)

  7. Experimental details (II) • Particle- coincidences NaI(Tl) Si E-E telescope  3He 45o Target nucleus

  8. The Oslo method • Unfold all  spectra † • Apply the first-generation method †† • Ansatz: first-gen. matrix  (E-E)T(E) ††† † : M. Guttormsen et al., NIM A374 (1996) 371 †† : M. Guttormsen et al., NIM A255 (1987) 518 ††† : A. Schiller et al., NIM A447 (2000) 498

  9. Normalizing the first-generation matrix Emin = 3.3 MeV E (MeV) 0 50V 4 8 0 4 8 E (MeV) Emax = 9.2 MeV E,min = 1.7 MeV

  10. Extraction of level density and -ray transmission coefficient The primary -ray matrix P(E, E) is factorized according to Theoretical approach:

  11. E E Input matrix P(E, E), 50V The resulting Pth(E, E), 50V E E Iteration method Minimize

  12. Quality of the iteration procedure 50V 44Sc

  13. Normalizing the level density • Low E: known, discrete levels • At Bn (or Bp): data from neutron (proton) resonance experiments

  14. Uncertainties in normalization • Calculation of (Un/p), spin cutoff parameter 1) 2) 3)

  15. Spin distributions, 44Sc A. Gilbert and A.G.W. Cameron, Can. J. Phys. 43, 1446 (1965) T. von Egidy and D. Bucurescu, Phys. Rev. C 72, 044311 (2005), Phys. Rev. C 73, 049901(E) (2006) S. Goriely, HF+BCS Demetriou and Goriely, Nucl. Phys. A695 (2001) 95 1) 2) 3)

  16. Level densities of 44,45Sc Preliminary

  17. Level densities of 50,51V Constant-temperature model

  18. Model to calculate the level density • Combining all possible proton and neutron configurations • Nilsson energy scheme • BCS quasiparticles Single q.p energy: Total energy due to q.p. excitations:

  19. Nilsson levels, 45Sc • Model parameters: • = 0.066 • = 0.32 [D.C.S. White et al., Nucl. Phys. A 260, 189 (1976)] • = 0.23 [In agreement with P. Bednarczyk et al., Phys. Lett. B 393, 285 (1997)]

  20. Calculated level densities, 44,45Sc

  21. Average number of broken pairs

  22. Parity asymmetry Defining the parity asymmetry as [U. Agvaanluvsan, G.E. Mitchell, J.F. Shriner Jr., Phys. Rev. C 67, 064608 (2003)] ~0.02 for (J=1/2, J=3/2)

  23. The -ray transmission coefficient Assuming dominance of dipole radiation (E1 and M1)

  24. Normalizing the -ray strength functions of 44,45Sc Data from J. Kopecky and M. Uhl: fE1 = 1.61(59)·10-8 MeV-3 fM1 = 1.17(59)·10-8 MeV-3

  25. Comparing with other data and theory 45Sc(,n)44Sc 46Ti(,p)45Sc

  26. The -ray strength functions of 50,51V Kadmenskij, Markushev and Furman: Lorentzian, spin-flip:

  27. Summary • Extraction of  and T from first-generation  spectra • Level densities of 44,45Sc and 50,51V • New model to calculate , Nqp,  • Gamma-ray strength functions of 44,45Sc and 50,51V

  28. Collaborators • Oslo: M. Guttormsen, S. Messelt, F. Ingebretsen, J. Rekstad, S. Siem and N.U.H. Syed • Åbo Akademi, Finland: T. Lönnroth • NSCL/MSU, USA: A. Schiller • Ohio University, USA: A. Voinov Thank you!

More Related