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Level Densities and -ray Strength Functions

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Presentation on theme: "Level Densities and -ray Strength Functions"— Presentation transcript:

1 Level Densities and -ray Strength Functions
Skulle jeg fortelle om all Sunniva Siem University of Oslo ISOLDE workshop 2007

2 Spin energy diagram In our experiments spin 2-6 ħ Bn Excitation energy
Yrast Spin ISOLDE workshop 2007

3 CACTUS- experimental setup
Reactions: (3He,) and (3He,3He’) Beam: MeV Targets: Yb, Dy, Er, Sm, Nd, Si, Mo, Fe, Sn, V, Pb,Ti,Ni 8 Si particle telescopes at = 45 ° Spin 2-6 ħ Bare nevne at GAMMASPHERE og EUROBALL, det største og beste Ge detektoroppsettene i vårt fagfelt har 10% effektivitet. Vi trenger ikke energioppløsningen til GS, så for våre eksperimenter finnes det ikke noe bedre oppsett i verden! CACTUS detector array (28 NaI + 2Ge) has 15% efficiency ISOLDE workshop 2007

4 Energy distribution of primary  rays contains info on:
level density ρ(Ef) -ray transmission coefficient T(E) Brink-Axel: P(Ex,E) ~T(E) ρ(Ef) Ex ISOLDE workshop 2007

5 ISOLDE workshop 2007

6 147Sm 146Sm ISOLDE workshop 2007

7 ISOLDE workshop 2007

8 ISOLDE workshop 2007

9 Microcanonical Temperature
ISOLDE workshop 2007

10 148Sm strength function Circles our data
Squares from photoabsorpsjon cross sections P.Carlos et al. NPA 225 (1974) Filled triangle is based on neutron capture in 147Sm ISOLDE workshop 2007

11 ISOLDE workshop 2007

12 ISOLDE workshop 2007

13 Scissors mode ISOLDE workshop 2007

14 ISOLDE workshop 2007

15 Radiative strength function of 57Fe
A.Voinov et al. Phys.Rev.Lett.93, (2004) ISOLDE workshop 2007

16 M.Guttormsen et al. Phys.Rev.C 71,044307(2005)
-strength functions in Mo isotopes Filled circles: (3He,α) Open circles: (3He,3He’) M.Guttormsen et al. Phys.Rev.C 71,044307(2005) ISOLDE workshop 2007

17 Summary Unique technique to extract level densities and -strength function experimentally New Sm data show that the level density continues to decrease as one approaches the N=82 closed shell The M1 pygmy resonance observed in deformed nuclei vanishes in the Sm nuclei as one approaches N=82 We still don’t understand the large enhancement in the strength function for low E in Fe, Mo and V isotopes ISOLDE workshop 2007

18 Future outlook New particle detector system, which will increase the efficiency 5-10 times Polarization measurments of the upbend in the strength function at low E, maybe with GRETINA or AGATA Study level density as a function of spin Investigate/test possibility of using inverse reactions Verify the electromagnetic character of the pygmy resonance. Use heavier beams to do pickup reactions/transfer reaktions. This vil bring in more spinn. Upgrade/refine the modell/technic/analysis to study the level density as a function of spinn. The next step is to do inverse reactions on ”heavier”(than 3He) targets, and ISOLDE workshop 2007

19 Collaborators R.Chankova, M.Guttormsen, F.Ingebretsen, S. Messelt, J.Rekstad, A.C.Larsen, N.U.H.Syed, S.Ødegård, University of Oslo A.Voinov, Dubna, Russia U.Agvaanluvsan, G.Mitchell, TUNL, USA J.A.Becker, L.Bernstein, LLNL, USA A.Schiller, MSU,USA T.Lønnroth, Åbo,Finland T.Belgya, Budapest, Hungary E.Algin, Turkey ISOLDE workshop 2007

20 Workshop on Level Density and Gamma Strength in Continuum
                                          Workshop on Level Density and Gamma Strength in Continuum Oslo, May , 2007 Experimental and theoretical topics on: - Level density - Radiative strength - Phase transitions in mesoscopic systems - Applications in astrophysics - Other related topics DEADLINES Abstract submission: March 1st 2007 Confirmed speakers: E. Algin Y. Alhassid F. Becvar A. Bracco F. Camera P. Chomaz T. Døssing T. von Egidy S. Frauendorf S. Grimes S. Harrisopulos K. Kaneko M. Krticka A. Lopez-Martens T. Lönnroth A. Maj G. Mitchell R. Pezer A. Richter A. Schiller A. Voinov J.-P. Wieleczko V. Zelevinsky S. Åberg ISOLDE workshop 2007

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