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E 0 DECAY OF THE 0 + 2 LEVELS IN 156 DY AND 160 ER G. Lo Bianco , S. Nardelli, S. Das Gupta,

E 0 DECAY OF THE 0 + 2 LEVELS IN 156 DY AND 160 ER G. Lo Bianco , S. Nardelli, S. Das Gupta, D.L. Balabanski, N. Blasi, K. Gladnishki, A. Saltarelli, L. Fortunato Lo Bianco potential. experiment: e−-  coincidences at LNS model calculations for transitional nuclei with the.

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E 0 DECAY OF THE 0 + 2 LEVELS IN 156 DY AND 160 ER G. Lo Bianco , S. Nardelli, S. Das Gupta,

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  1. E0 DECAY OF THE 0+2LEVELS IN 156DY AND 160ER G. Lo Bianco, S. Nardelli, S. Das Gupta, D.L. Balabanski, N. Blasi, K. Gladnishki, A. Saltarelli, L. Fortunato Lo Bianco potential • experiment: e−- coincidences at LNS • model calculations for transitional nuclei with the

  2. The mini-orange spectrometer at LNS

  3. E0 operator: observables: 2(E0), r2 J.L.Wood et al., NPA651, 323 (1999)

  4. very few data on E0 strength!

  5. average of the N = 90 nuclei (150Nd, 152Sm, 154Gd, 156Dy, 158Er) average of the N = 92 isotones average of “good” rotors in the rare-earth and the actinide region B(E2; yrast)/B(E2;rotor)

  6. 42 = J.O.Rasmussen, NP 19, 85 (1960) T. Kibedi et al., NPA567, 183 (1994) Ω : J. Kentele, NIM A271, 625 (1988) Obvious approach: Measure spectra of conversion electrons!

  7. beam target Mini-orange  spectrometer J.van Klinken and K. Wisshak, Nucl. Instr. Meth. 98 (1972) 1

  8. 56 min 19.5 min 156Dy ← 156Ho← 156Er 160Er ← 160Tm ← 160Yb 4.8 min 9.4 min Experiment enhanced population of low-spin non-yrast states populated in (HI,xn)-reaction the  decay goes through low-spin states

  9. Measurements and calibrations • absolute efficiency calibration of Ge detectors; • in-beam and off-beam -ray spectra; • in-beam electron spectra for determination of the transmission curve; • off-beam electron spectra for ICC measurements and X(E0/E2) calculation; • independent ICC calibration, e.g. 124Sn(12C,4n)132Ba.

  10. -ray spectrum electron spectrum 156Dy

  11. 156Dy Off-beam ICC Spectrum: 0+2 → 0+1 transition in 156Dy

  12. Results for 156Dy PhD thesis of Sara Nardelli, Camerino 2010

  13. 160Er -ray spectrum Number of counts electron spectrum Energy in KeV

  14. 160Er : 768K(710.5KeV) 160Dy: 766K (713KeV) 160Er: 837.0 KeV X value:X = 0.19(7), after a careful consideration of all possible contaminants PhD work of Shinjinee Das Gupta, Camerino

  15. Results T. Kibedi, R.H. Spear, ADNDT 89, 77 (2005)

  16. X(5) is a solution of the Bohr Hamiltonian with a special choice of a potential v(,) = u() + v() F.Iachello, Phys. Rev. Lett. 87, 052502 (2001) For the U(5) – SU(3) shape phase transition, a more general potential in  was chosen u() = V0(4 - 203+ (1 - )022); 0   1; critical point at  =1/2 Lo Bianco potential

  17. spherical side close to the critical point

  18. Results of the calculations a factor of 4 difference with experiment; * same true for the -soft model Bonnet et al., 79, 034307 (2009)

  19. Conclusions and outlook • A reliable technique for ICC measurements was developed at the INFN LNS – Catania; • First results for the X(E0/E2) ratio in 156Dy and 160Er were obtained; • Calculations with a generalized potential in  were performed, which allows to map the U(5) – SU(3) phase shape transition; • Further ICC measurements, as well as lifetime measurements of 0+ states are in the pipeline.

  20. Thank you !

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