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Experimental techniques to deduce J Joint ICTP-IAEA Workshop on Nuclear Structure and Decay Data Theory and Evaluation 28 April - 9 May 2008 Tibor Kibdi

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Outline: Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Lecture I: Experimental techniques to deduce J from Internal Conversion Coefficients Angular distributions and correlations Directional Correlations from Oriented nuclei (DCO) Lecture II: New developments in characterizing nuclei far from stability

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Electromagnetic Decay and Nuclear Structure Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 E i J i E f J f E , L, Angular momentum and parity selection rules; multipolarities |J i - J f | L J i + J f ; L 0 J i = J f = no;E2, E4, E6 M1, M3, M5E0 = yes; E1, E3, E5 M2, M4, M6 Energetics of -decay: E i = E f + E + T r 0 = p r + p where T r = (p r ) 2 /2M; usually T r /E ~10 -5 Mixed multipolarity ( `L`) = I ( `L`) / I ( L) Multipolarity known J may not be unique unique

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Electromagnetic decay modes Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Angular distribution with spins oriented Angular correlations Polarization effects -ray

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Electromagnetic decay modes Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Electron conversion coefficients E0 transitions: L=0 electron conversion Angular distribution with spins oriented Angular correlations Polarization effects -ray K L M

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Pair conversion coefficients E0 transitions: L=0 Electromagnetic decay modes Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Electron conversion coefficients E0 transitions: L=0 electron conversion Angular distribution with spins oriented Angular correlations Polarization effects -ray K L M e - - e + pair Higher order effects: for example 2 photon emission is very weak

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Angular distributions of Gamma-rays Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Mixing ratio ( L/ `L`) = I ( `L`) / I ( L) 2 2 transition Mixed, L=1, L`=2

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Angular distributions of Gamma-rays Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Mixing ratio ( `L`) = I ( `L`) / I ( L) Mixing ratio ( L/ `L`) = I ( `L`) / I ( L) 2 1 transition Mixed, L=1, L`=2

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Angular distributions of Gamma-rays Tibor Kibdi, Dep. of Nuclear Physics, Australian National University 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 ICTP-IAEA Workshop 7-May-2008 Attenuation due to relaxation of nuclear orientation For F k (LL`J f J i ) see E. Der Mateosian and A.W. Sunyar, ADNDT 13 (1974) 391

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Angular distributions of Gamma-rays (n,n ) reaction on 92 Zr Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Gas Cell 3 H(p,n) @ E p = 4.9 MeV E n = 3.9 MeV Sample (41 gr) Pulsed Proton beam Tungsten Copper Lead Ring Polyethylene Annular BGO HPGe Detector n` = 40 - 150 C. Fransen, et al., PRC C71, 054304 (2005) at Univ. of Kentucky Figure courtesy of S.W. Yates

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Angular distributions of Gamma-rays (n,n ) reaction on 92 Zr Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 C. Fransen, et al., PRC C 71, 054304 (2005), at Univ. of Kentucky Fit to data 92 Zr(n,n`) reaction 12 angles and 12 hours / angle -spectrometer at 1.4 m Deduced A 2 =A 22 /A 0 A 4 = A 44 /A 0 Typical valuesA2A4 J=2 (stretched quadrupole) +0.3-0.1 J=1 (stretched dipole) -0.20 J=1, D+Q +0.5 to -0.8>0 E = 2123.0 keV

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Angular distributions mixing ratio Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Mixing ratio, deduced from 2 of as a function of But no information on Electric or Magnetic character: E1+M2 or M1+E2 = 0.69(16) (D+Q) Beam defines a symmetry axis where B k (J) is the statistical tensor Approximation with Gaussian distribution E = 2123.0 keV

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Directional Correlations from Oriented nuclei (DCO) Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 L 2 L 2 2 J1J1 J2J2 J3J3 L 1 L 1 1 ` ` For a J 1 J 2 J 3 cascade (see A.E. Stuchbery, Nucl. Phys. A723 (2003) 69) 1 (k 1 ) 2 (k 2 ) xkxk ykyk zkzk

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Directional Correlations from Oriented nuclei (DCO) example Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 184 Pt from nat Gd + 29 Si @ 145 MeV CAESAR array (ANU) M.P. Robinson et al., Phys. Lett B530 (2002) 74 10 + 8+8+ 6+6+ 4+4+ 2+2+ 0+0+ 11 2 ( ) 2 ( ) 2 ( )

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Directional Correlations from Oriented nuclei DCO ratio Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 L 2 L 2 2 J1J1 J2J2 J3J3 L 1 L 1 1 ` ` By ignoring dependence we get 1 (k 1 ) 2 (k 2 ) xkxk ykyk zkzk DCO L 1 = L 2 1 L 1 =1 & L 2 =2~2 For stretched transitions

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Conversion electrons (CE) Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 -ray K L M r Radial distribution of EWF free particle electron bound state electron Electron conversion Energetics of CE-decay (i=K, L, M,.) E i = E f + E ce,i + E BE,i + T r - and CE-decays are independent; transition probability T = + CE = + K + L + M Conversion coefficient i = CE,i /

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The physics of conversion coefficients Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Nuclear Electron Multipolar source Same for and CE Fermis golden rule bound state electron free particle electron Density of the final electron state (continuum)

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Sensitivity to transition multipolarity Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 K NOT SELECTIVE i depends on 1)Transition energy ( E 2)Atomic number ( 3)Multipol order (L; the angular momentum carried away) 4)Electric (E ) or magnetic (M ) character 5)The shell or subshell the electron is ejected 6)Atomic screening 7)Nuclear structure effects (penetration) NOTE (3) and (4) often referred as multipolarity L)

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Mixed multipolarity and E0 transitions Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 In some cases the mixing ratio can be deduced E0 transitions pure penetration effect; no -rays (I =0) Pure E0 transition: 0 + 0 + or 0 - 0 - J J (J0) transitions can be mixed E0+E2+M1

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Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 134.363(18) keV M1+E2 transition in 172 Yb 2 (MR) hyper surface MR=1.3(3) (ENSDF) MR=1.52(24) (BrIccMixing from Chi-squared fit) MR=1.5(+12-4) (BrIccMixing from 2 (MR) hyper surface) CE data 1968Ka01 K 0.63(16) 1968Ka01 L1/L2 0.62(19) 1968Ka01 L2/L3 1.3(3)

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More on conversion coefficients Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Conversion coefficient i = CE,i / Total conversion coefficient T K L M + .+ K-shell L1-shell M1-shell Electron- positron pair production Z=30 (Zn) E2 Fewer electrons than -rays

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Measuring conversion coefficients - methods Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 NPG: normalization of relative CE (I CE,i ) and (I ) intensities via intensities of one (or more) transition with known CEL: Coulomb excitation and lifetime measurement XPG: intensity ratio of K X-rays to -rays with K-fluorescent yield, K And many more, see Hamilton`s book

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Internal Conversion Process the Pioneers Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 May 1965, Vanderbilt University, Nashville, Tennessee T.R. Gerholm M.E. Rose J.H. Hamilton E.F. Zganjar M. Sakai E. Seltzer & R. Hager

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Conversion electron spectroscopy with PACES Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Based on new data, favoured interpretation is that isomer is not a high-K, but K =0 + Electrons are vital! Built by E. Zganjar, LSU channel number (0.6 keV/ch) Figure courtesy of P.M. Walker (Surrey) and P. Garrett (Guelph) K/L(E3) ~ 0.3

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Magnetic spectrometers Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Mini-orange (looks like a peeled orange) transmission > 20% small size and portability, but poorer quality Superconducting solenoid Broad-range mode 100 keV up to a few MeV Lens mode finite transmitted momentum bandwidth ( p/p~15-25%) high peak-to-background ratio ATOMKI, Debrecen

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Super-e Lens (ANU) Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008

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Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Super-e Lens (ANU) 194 Pt( 12 C,4n) 202 Po @ 76 MeV Pulsed beams (~1 ns) with 1.7 s separation

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The SACRED Electron Spectrometer (Liverpool-JYFL) Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 H. Kankaanp et al., NIM A534 (2004) 503 see also P.A. Butler et al., NIM A381 (1996) 433

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The SACRED array example Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Sacred + RITU recoil tagged CE 208 Pb( 48 Ca,2n) 254 No S. Eeckhaudt, et al., Eur. Phys. J. A 25, 605 (2005) P.A. Butler, et al., Phys. Rev. Lett. 89, 202501 (2002)

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Super-e & Honey (ANU) Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Electrons from atomic collisions are the major difficulty in low energy CE spectroscopy using ion induced reactions HPGe

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Super-e Honey (ANU) ee coincidences Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 63.1 LM 63.1 Gate on ALL gammas Gate on ALL CE E =63.1 keV transition not visible in the gamma spectrum T (M1) = 7.3! K-shell conversion not allowed BE K =90.5 keV 208 Pb(p,n) 208 Bi @ 9 MeV K.H. Maier et al, Phys. Rev. C 76, 064304 (2007)

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Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Super-e Honey (ANU) ee coincidences 538.2 63.1 LM 63.1 Gate on 538.2 keV gammas Gate on 63 LM CE Gate on 538.2 keV gammas Gate on 63 LM CE 63.1 63.1 LM

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ICC from total intensity balances example 1 Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Out-of-beam (or decay) coincidence data OUT IN 228/463 1085/463

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ICC from total intensity balances when to use Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 K L M N Be careful near energies close to shell binding Accuracy of gamma-ray measurements controls the range of its use E1 M1 E2 M2 E3 M3 I /I ~ 10%

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ICC from total intensity balances example 2 Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 In-beam: only when gating from above 577/611 207/311 Side feeding

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ICC from X- and -ray intensities Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 Vacancies in the atomic shell give rise to rearrangements in the shells which are accompanied by the emission of X-rays Auger electrons B Schnfeld and h. Jansen, Nucl. Instr. and Merh. in Phys. Res. A 369 (1993) 527. K x-rays: K (K-L shells) Kb (K-M, K-MN, etc. shells)

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ICC from X- and -ray intensities Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 661.657 Ba-KX 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

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Acknowledgements Tibor Kibdi, Dep. of Nuclear Physics, Australian National University ICTP-IAEA Workshop 7-May-2008 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)