Search for the Exotic Wobbling Mode in 171 Re

1. Search for the Exotic Wobbling Mode in 171Re MIDN 1/C Eowyn Pedicini, USN Advisers: Professor Daryl Hartley LT Brian Cummings, USN

2. Outline • Motivation • Experimental Details • Data Preparation/Analysis • Results • Conclusion and Future Work

3. Most nuclei have at least one axis of symmetry Five nuclei have been found to be asymmetric Symmetry in Nuclei (Doorknob) (Football)

4. EXPERIMENTAL DETAILS

5. Heavy Ion Reaction 120Sn + 55Mn 175Re 171Re + 4n + γ Target Nucleus (120Sn) Beam Nucleus (55Mn) 4 neutrons boiloff Rotating CompoundNucleus (175Re) Nucleus emits γ rays to slow spin

6. TARGET BEAM LINE Gammasphere • Germanium detectors detect γ rays in coincidence (120 ns) • Coincidence event is where multiple detectors fire at once • 100 detectors to get full coverage

7. Data Preparation • Detectors must be checked against each other to ensure accuracy and consistency • Calibrate the detectors with standard γ-ray sources • Sort into Blue database • 3-fold up to 15-fold events saved in files

8. Detector Calibration y = -3.307x10-7*x2 + 6.675x10-1*x - 2.851x10-1

9. Data Preparation Detectors must be checked against each other to ensure accuracy and consistency Calibrate the detectors with standard γ-ray sources Sort into Blue database 3-fold up to 15-fold events saved in files

10. Data Preparation (cont.) • Determine efficiency of detectors • Not constant for all energies Relative Efficiency Energy (keV)

11. Correction for Doppler Shifts E (θ) = hf E (θ) =Eo(1+βcos(θ)) β = (speed of nucleus)/(speed of light) θ= Angle at which detectors were relative to target v = 0.0289 c

12. As nucleus slows, it emits discrete sequence of γ rays Which sequence do the γ rays go in? In what order? Coincidence matrix created from the Blue database Band Construction

13. Gating • Level scheme was built using “gates” in the coincidence matrix

14. Construction of 171Re Level Scheme

15. Shell Model • Nucleons are arranged in shells (s1/2, d3/2, etc.) • Nucleons paired in time-reversed orbits • Angular momentum sums to zero • 171Re has 96 neutrons and 75 protons • Different protons can be unpaired • Different protons give rise to different sequences

16. ix Configuration Assignments • Alignment (ix), is the amount of angular momentum of unpaired particle about the rotation axis

17. Alignment Plots

18. Wobbling band? Configuration Assignments h9/2 d3/2 i13/2 d3/2 (AB) d5/2 h11/2

19. What is wobbling? i13/2 band Wobbling band • Based on i13/2 proton • Angular momentum off-axis • Nucleus “wobbles” like an asymmetric top 163Lu S. W. Ødegård et al., Physical Review Letters 86, 5866 (2001).

20. History of Wobbling • First found in 163Lu • Subsequently found in 161,165,167Lu (N~94) • Not found in several Ta, Hf, Tm isotopes • Recently found in 167Ta (N=94)

21. Is Band 6 a Wobbling Band? • Alignment tracks that of the i13/2 band, but does not match exactly • Moment of inertia also follows the i13/2 band • Not likely that Band 6 is a wobbler, but if it is, it is different from all other observed wobblers i13/2 band wobbling band?

22. 163Lu 171Re

23. Future Work • Questions still remain as to whether 171Re has an asymmetric nucleus • Need another experiment (run for several days) to gather enough data

24. Acknowledgments • Professor Hartley • LT Cummings • NSF

25. Questions?

27. PACE Calculations

28. Gain Shifts

29. Angular Correlation Ratios

30. Time-reversed Orbits

31. Shell Model

33. Previous Level Scheme for 171Re

34. Spectra for Bands 4 and 5

35. ix(ω) = Ix(ω) – Ixref(ω) = ωJ0 + ω3J1 Configuration Assignments

36. Band Crossings

37. Band Crossings (cont.)

38. Identifying a Wobbling Band • Similar moment of inertia (J) as i13/2 band • Hundreds, if not thousands of gates will be taken 165Lu i13/2 Wobbling band