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Experimental techniques to deduce J p

Experimental techniques to deduce J p. Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data Theory and Evaluation 28 April - 9 May 2008 Tibor Kibédi. Outline:. Lecture I: Experimental techniques to deduce J p from Internal Conversion Coefficients

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Experimental techniques to deduce J p

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  1. Experimental techniques to deduce Jp Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data Theory and Evaluation 28 April - 9 May 2008 Tibor Kibédi

  2. Outline: • Lecture I:Experimental techniques to deduce Jp from • Internal Conversion Coefficients • Angular distributions and correlations • Directional Correlations from Oriented nuclei (DCO) Lecture II: New developments in characterizing nuclei far from stability Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  3. Ei Ji Eg, L, Dp p Ef Jf Electromagnetic Decay and Nuclear Structure • Energetics of g-decay: • Ei = Ef + Eg + Tr • 0 = pr + pg, • where Tr = (pr)2/2M; usually Tr/Eg~10-5 p • Angular momentum and parity selection rules; multipolarities • |Ji - Jf| ≤ L ≤ Ji + Jf; L ≠ 0 Ji = Jf • Dp = no; E2, E4, E6 M1, M3, M5 E0 • Dp = yes; E1, E3, E5 M2, M4, M6 Multipolarity known DJmay not be unique uniqueDp • Mixed multipolarity • d(p`L`) = Ig(p`L`) / Ig(pL) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  4. Electromagnetic decay modes • Angular distribution with spins oriented • Angular correlations • Polarization effects g-ray Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  5. Electromagnetic decay modes • Electron conversion coefficients • E0 transitions: DL=0 • Angular distribution with spins oriented • Angular correlations • Polarization effects g-ray electron conversion L M K Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  6. Electromagnetic decay modes • Electron conversion coefficients • E0 transitions: DL=0 • Angular distribution with spins oriented • Angular correlations • Polarization effects • Pair conversion coefficients • E0 transitions: DL=0 g-ray electron conversion e- - e+ pair L M K Higher order effects: for example2 photon emission is very weak Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  7. Angular distributions of Gamma-rays 2 → 2 transition Mixed, L=1, L`=2 Mixing ratio d(pL/p`L`) = Ig(p`L`) / Ig(pL) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  8. Angular distributions of Gamma-rays 2 → 1 transition Mixed, L=1, L`=2 Mixing ratio d(pL/p`L`) = Ig(p`L`) / Ig(pL) Mixing ratio d(p`L`) = Ig(p`L`) / Ig(pL) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  9. Angular distributions of Gamma-rays Attenuation due to relaxation of nuclear orientation For Fk(LL`JfJi) see E. Der Mateosian and A.W. Sunyar, ADNDT 13 (1974) 391 • Nuclear orientation can be achieved • by interaction of external fields (E,B) with the static moments of the nuclei at low temperatures • by nuclear reaction Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  10. Tungsten Polyethylene Copper HPGe Detector Lead Ring Annular BGO Angular distributions of Gamma-rays(n,n) reaction on 92Zr ‘ n` Sample (41 gr) Pulsed Proton beam θ = 40° - 150 ° Gas Cell 3H(p,n) @ Ep = 4.9 MeV En = 3.9 MeV Figure courtesy of S.W. Yates C. Fransen, et al., PRC C71, 054304 (2005) at Univ. of Kentucky Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  11. Angular distributions of Gamma-rays(n,n) reaction on 92Zr ‘ 92Zr(n,n`) reaction 12 angles and 12 hours / angle g-spectrometer at 1.4 m Eg = 2123.0 keV Fit to data C. Fransen, et al., PRC C 71, 054304 (2005), at Univ. of Kentucky Deduced A2=A22/A0 A4 = A44/A0 Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  12. Mixing ratio, d deduced from 2 of as a function of d But no information on Electric or Magnetic character: E1+M2 or M1+E2 Angular distributions – mixing ratio ‘ Beam defines a symmetry axis where Bk(J) is the statistical tensor Eg = 2123.0 keV Approximation with Gaussian distribution • = 0.69(16) (D+Q) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  13. g2(k2) g1(k1) Directional Correlations from Oriented nuclei (DCO) ‘ zk J1 2 1 L1 L1d1 ` J2 L2 L2d2 ` yk 1 J3 2 xk For a J1→ J2→ J3 cascade(see A.E. Stuchbery, Nucl. Phys. A723 (2003) 69) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  14. 10+ g1 8+ g2 (□) 6+ g2 (●) 4+ g2 (○) 2+ 0+ Directional Correlations from Oriented nuclei (DCO) example ‘ 184Pt from natGd + 29Si @ 145 MeV CAESAR array (ANU) M.P. Robinson et al., Phys. Lett B530 (2002) 74 Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  15. g2(k2) g1(k1) Directional Correlations from Oriented nuclei DCO ratio zk J1 2 1 L1 L1d1 ` J2 L2 L2d2 ` yk 1 J3 2 xk By ignoring  dependence we get For stretched transitions Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  16. bound state electron free particle electron Conversion electrons (CE) Radial distribution of EWF g-ray Electron conversion K L M r • Energetics of CE-decay (i=K, L, M,….) • Ei = Ef + Ece,i + EBE,i + Tr • g- and CE-decays are independent; transition probability • lT = lg + lCE = lg + lK + lL + lM…… • Conversion coefficient • ai = lCE,i / lg Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  17. Fermi’s golden rule bound state electron free particle electron The physics of conversion coefficients Density of the final electron state (continuum) Electron Nuclear Multipolar source Same for  and CE Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  18. Sensitivity to transition multipolarity • ai depends on • Transition energy (Eg) • Atomic number (Z) • Multipol order (L; the angular momentum carried away) • Electric (El) or magnetic (Ml) character • The shell or subshell the electron is ejected • Atomic screening • Nuclear structure effects (penetration) • NOTE (3) and (4) often referred as multipolarity (pL) aKNOT SELECTIVE Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  19. Mixed multipolarity and E0 transitions In some cases the mixing ratio can be deduced E0 transitions – pure penetration effect; no g-rays (Ig=0) • Pure E0 transition: 0+ → 0+ or 0- → 0- • J → J (J≠0) transitions can be mixed E0+E2+M1 Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  20. 134.363(18) keV M1+E2 transition in 172Yb 2(MR) hyper surface CE data 1968Ka01 K 0.63(16) 1968Ka01 L1/L2 0.62(19) 1968Ka01 L2/L3 1.3(3) MR=1.3(3) (ENSDF) MR=1.52(24) (BrIccMixing from Chi-squared fit) MR=1.5(+12-4) (BrIccMixing from Χ2(MR) hyper surface) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  21. M1-shell Z=30 (Zn) E2 L1-shell K-shell Electron-positron pair production • Conversion coefficient • ai = lCE,i / lg • Total conversion coefficient • aT = aK + aL + aM + ….+ap Fewer electrons than g-rays More on conversion coefficients Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  22. Measuring conversion coefficients - methods • NPG: normalization of relative CE (ICE,i) and g (Ig) intensities via intensities of one (or more) transition with known a • CEL: Coulomb excitation and lifetime measurement • XPG: intensity ratio of K X-rays to g-rays with K-fluorescent yield, K And many more, see Hamilton`s book Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  23. Internal Conversion Process – the Pioneers E. Seltzer & R. Hager E.F. Zganjar T.R. Gerholm M.E. Rose J.H. Hamilton M. Sakai May 1965, Vanderbilt University, Nashville, Tennessee Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  24. Conversion electron spectroscopy with PACES Based on new data, favoured interpretation is that isomer is not a high-K, but Kp=0+ Electrons are vital! K/L(E3) ~ 0.3 Built by E. Zganjar, LSU Figure courtesy of P.M. Walker (Surrey) and P. Garrett (Guelph) channel number (0.6 keV/ch) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  25. Magnetic spectrometers • Superconducting solenoid • Broad-range mode – 100 keV up to a few MeV • Lens mode – finite transmitted momentum bandwidth (Dp/p~15-25%) – high peak-to-background ratio • Mini-orange (looks like a peeled orange) • transmission > 20% • small size and portability, but poorer quality ATOMKI, Debrecen Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  26. Super-e Lens (ANU) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  27. Super-e Lens (ANU) 194Pt(12C,4n)202Po @ 76 MeV Pulsed beams (~1 ns) with 1.7 ms separation Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  28. The SACRED Electron Spectrometer (Liverpool-JYFL) H. Kankaanpää et al., NIM A534 (2004) 503 see also P.A. Butler et al., NIM A381 (1996) 433 Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  29. 208Pb(48Ca,2n)254No S. Eeckhaudt, et al., Eur. Phys. J. A 25, 605 (2005) The SACRED arrayexample P.A. Butler, et al., Phys. Rev. Lett. 89, 202501 (2002) Sacred + RITU recoil tagged CE Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  30. Super-e & Honey (ANU) Electrons from atomic collisions are the major difficulty in low energy CE spectroscopy using ion induced reactions HPGe Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  31. Super-e Honey (ANU)eeg coincidences Gate on ALL CE Eg=63.1 keV transition not visible in the gamma spectrum aT(M1) = 7.3! Gate on ALL gammas 63.1 g: aT(M1)= 7.3 K-shell conversion not allowed BEK=90.5 keV 63.1 LM 208Pb(p,n)208Bi @ 9 MeV K.H. Maier et al, Phys. Rev. C 76, 064304 (2007) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  32. Gate on 63 LM CE Super-e Honey (ANU)eeg coincidences Gate on 63 LM CE 538.2 Gate on 538.2 keV gammas 63.1 g: aT(M1)= 7.3 Gate on 538.2 keV gammas 63.1 g: aT(M1)= 7.3 63.1 LM 63.1 LM Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  33. ICC from total intensity balances –example 1 t Out-of-beam (or decay) coincidence data 228/463 1085/463 IN OUT Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  34. ICC from total intensity balances – when to use • Be careful near energies close to shell binding • Accuracy of gamma-ray measurements controls the range of its use M3 M2 E3 E2 M1 E1 dIg/Ig ~ 10% M N L K Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  35. ICC from total intensity balances –example 2 In-beam: only when gating from “above” 577/611 Side feeding 207/311 Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  36. ICC from X- and g-ray intensities • Vacancies in the atomic shell give rise to rearrangements in the shells which are accompanied by the emission of • X-rays • Auger electrons K x-rays: Ka (K-L shells) Kb (K-M, K-MN, etc. shells) B Schönfeld and h. Jansen, Nucl. Instr. and Merh. in Phys. Res. A 369 (1993) 527. Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  37. 661.657g Ba-KX ICC from X- and g-ray intensities • Singles gamma measurement • No other photon and/or contaminates • Well calibrated spectrometer • Correct treatment of the photon attenuation, scattering, etc. • Knowledge of the fluorescence yield N. Nica, et al. Phys. Rev. C75 (2007) 024308 Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

  38. Acknowledgements G.D. Dracoulis , G.J. Lane, P. Nieminen, H. Maier (ANU) F.G. Kondev (ANL) P.E. Garrett (University of Guelph and TRIUMF) S.W. Yates (Univ. of Kentucky) Tibor Kibèdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop7-May-2008

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