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Picosecond Lifetime Measurements in ‘Vibrational’ Cadmium and Palladium Isotopes

Picosecond Lifetime Measurements in ‘Vibrational’ Cadmium and Palladium Isotopes. Paddy Regan Department of Physics, University of Surrey Guildford, GU2 7XH, UK p.regan@surrey.ac.uk. Survey of Even-Even Cadmium Isotopes. A. Aprahamian et al., Phys. Lett. B 140 , 22 (1984). D i x = 10 h

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Picosecond Lifetime Measurements in ‘Vibrational’ Cadmium and Palladium Isotopes

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  1. Picosecond Lifetime Measurements in ‘Vibrational’ Cadmium and Palladium Isotopes Paddy Regan Department of Physics, University of Surrey Guildford, GU2 7XH, UK p.regan@surrey.ac.uk

  2. Survey of Even-Even Cadmium Isotopes A. Aprahamian et al., Phys. Lett. B 140, 22 (1984)

  3. Dix= 10 h = (nh11/2)2 Nomically ‘vibrational’ nuclei agree very well with CSM, (rotational) description.

  4. Odd-A Cadmium Isotopes: Vibrators or Rotors ? • Odd-A Cd A = 105 – 123, all have a ‘rotational’ bands built upon the 11/2-state • For 105-109Cd, from the B(E2: 15/2-→11/2-) value rotational structure associated with rotational alignment coupling (RAC)† • B(E2: 15/2-→11/2-) for 107Cd suggests coupling of unpaired neutron to vibrational core (PVC)‡ † D.C. Stromswold et al, Phys. Rev. C 17 (1978) 143 F.M. Stephens, R.M. Diamond, S.G. Nilsson, Phys Lett B 44 (1973) 429 ‡ O. Häusser et al, Phys Lett B52 (1974) 329 G. Alaga, V. Paar, V. Lopac, Phys Lett B43 (1973) 459 G. Dracoulis, R. Chapman et al., Part. Nucl. 4 (1972) 42

  5. Crossing and alignments well reproduced by CSM, but AHVs see PHR et al., Phys. Rev. C68 (2003) 044313

  6. Dix=10h PHR, Beausang, Zamfir, Casten, Zhang et al., Phys. Rev. Lett. 90 (2003) 152502

  7. E-GOS plot appears to indicate that Vibrator-Rotator phase change is a feature of near stable (green) A~100 nuclei. BUT….what is the microscopic basis ? ‘Rotational alignment’ can be a crossing between quasi-vibrational GSB & deformed rotational sequence. (stiffening of potential by population of high-j, equatorial (h11/2) orbitals). PHR, Beausang, Zamfir, Casten, Zhang et al., Phys. Rev. Lett. 90 (2003) 152502

  8. 82 1h11/2 50 [550]1/2- 1g9/2 jx Alignment (rotational picture at least) driven byCoriolis interactionon high-j, low-Worbitals (ie. ones with large jx on collective rotation axis. Vcor = -jx.w eg. nh11/2 [550]1/2 ‘intruder’ FS for N~57, b2~0.15->0.2 [541]3/2- see PHR, G.D. Dracoulis et al., J. Phys. G19 (1993) L157

  9. seems to work ok, nh11/2 bands now look like rotors, Even-even yrast sequences and odd-A +ve parity only show rotational behaviour after (nh11/2 )2 crossing…. PHR, C. Wheldon et al., Acta Phys. Pol. B36 (2005) 1313

  10. B(E2) Signatures of Collectivity • For a perfectly harmonic oscillator: • For axially deformed rotor (Bohr and Mottelson) : • For U(5) of the IBA (valence limited case, see Casten and Warner, Rev. Mod. Phys. 60 (1988) 389 ; Kern et al., Nuc. Phys. A593 (1995) 21 .)

  11. Vibrator: Rotor: Vibrator U(5) limit (for 106Cd): Rotor U(5) limit (for 106Cd) B(E2: I -> 1-2) Theoretical Limits

  12. Recoil (Doppler) Distance Method Es 98Mo 12C @ 60MeV θ E0 98Mo(12C, xn)110-xCd 98Mo(12C, αxn)106-xPd

  13. SPEEDY and NYPD SPEEDY γ-ray array, 4 clovers each at 41.5° and 138.5°. New Yale Plunger Device: Thin target + 197Au stopper. Piezoelectric motor to control target-stopper distance. Capacitance measured to give accurate distance value. R. Krucken et al.,J. Res. Nat. Inst. St.Tech. 105 (2000) 53.

  14. RDM and DSAM Expts. at WNSL, August 2004 • Experiment to determine the various B(E2) values of 103,4Pd and 106,7Cd • Fusion-evaporation reaction used to produce the nuclei of interest 98Mo(12C,3n)107Cd + ,p2n)107Ag 98Mo(12C,4n)106Cd + ,p3n)106Ag 98Mo(12C,α2n)104Pd 98Mo(12C,α3n)103Pd

  15. RDM and DSAM Expt. at WNSL, August 2004 • RDM, 98Mo target, ~900 μg/cm2 ,v/c~0.7-.8% (~2 mm/ps) • DSAM, 98Mo target.~500 μg/cm2 on 9 mg/cm2197Au. • Distances 11, 14, 18, 23, 28, 41, 56, 127, 330, 2008 mm.. (tof)~ 22, 28, 36,46, 56, 82, 102, 154, 660, 4000 ps) • 2 coincident γ-ray events within a time window of ~ 50ns • (q a ‘ qb) matrices sorted for each plunger distance

  16. Differential Decay Curve Method (DDCM) • Lifetime deduced from following equation: where • For an intra-band direct feeding transition, the above equation reduces to Gate Ihi = Uhi + Shi Iij = Uij + Sij G. Bohm, A. Dewald et al., NIM A329 (1993) 248 S. Harrissopulos, Nucl. Phys. A683 (2001) 157

  17. Differential Decay Curve Method G. Bohm, A. Dewald et al., NIM A329 (1993) 248 Nomenclature: U denotes “Unshifted” Transition S denotes “Shifted” Transition Direct Gating (on SB) from above A B C

  18. Inaccurate lifetimes may be obtained, for 2+ or 4+ gated due to “de-orientation’’. Differential Decay Curve Method Direct Gating (on UC) from below A B C

  19. 60 MeV beam energy

  20. 104Pd: N=58 W. Andrejtscheff et al, Nucl. Phys. A448 (1986), 301 J.A. Grau et al, Phys. Rev. C14 (1974), 2297

  21. Lifetime Plots for 2+→ 0+ in 104Pd forward backward Average τ = 14.7(1.0)ps B(E2:2-0) = 36(2) W.u. S. Raman et al., At.Data Nucl.Data Tab. 36 1 (1987) t (2+, 104Pd) = 14.3(9)ps, 

  22. RDM DDCM Lifetime Analysis in 107Cd 19/2- 798keV 15/2- 515keV 11/2-

  23. D.C. Stromswold et al, Phys. Rev. C17 (1978) 143

  24. DDCM Lifetime Analysis in 107Cd 515 keV 798 keV = 28.2(1.0)W.u. = 24.5(4.3) W.u. K. Andgren, S.F.Ashley, PHR, E. McCutchan et al., in press J. Phys. G (2005) cf. t(15/2-) = 23.5(1.5)psO. Häusser et al, Phys Lett B52 (1974) 329

  25. t~0.36(6)ps very preliminary !! not to be quoted = 99.6 (16.5) W.u. !! DSAM data can give information on higher lying (<1ps) lifetimes in 107Cd. Unevaluted report for 956 keV decay of Vishnevsky et al., ,Sov. Jour. Nucl. Phys. 54, 191 (1991) gives t=1.15(43)ns -> B(E2:23/2- ->19/2-) = 30(11)Wu.

  26. B(E2) ratio plot for 11/2- band in 107Cd B(E2: 15/2 -> 11/2) = 0.085e2b2 = 28.2(1.0) Wu B(E2: 19/2 -> 15/2) = 0.074e2b2 = 24.5(4.3) Wu B(E2: 23/2 -> 19/2) ~ 0.280e2b2 = 100(17) Wu Vibrational Axial symmetric perfect rotor U(5) limit for 106Cd

  27. 106Cd Challenges: Isomers • τ= 90ns, four quasi-particle isomer at 4660 keV (12+) • Various, ns isomers, associated with two quasi-particle configurations which feed low-lying states W. Andrejtscheff et al, Nucl. Phys. A437 (1985), 167

  28. 106Cd Challenges: Doublets P.H. Regan et al, Nucl. Phys. A586 (1995), 351

  29. 106Cd: High Spin States

  30. 602 keV 12+ ->10+ t (12+)= 13(1) ps -> B(E2:12->10)= 27(2) Wu

  31. ‘nti-magnetic rotation in 106Cd, A. Simons, R. Wadsworth et al., PRL 91 (2003) B(E2:2+ –>0+) = 27 Wu B(E2:4+->2+) = 44 Wu B(E2:12+–>10+) = 27(2) Wu B(E2:18+->16+) = 50(4) Wu B(E2:20+->18+) = 47(6) Wu B(E2:22+->20+) = 27(2) Wu B(E2:24+->22+) = 20(2) Wu

  32. Conclusions • RDM (+DSAM) for B(E2)s in 106,7Cd, 103,4Pd • B(E2) values for the 19/2- and 15/2- states in 107Cd suggests rotational behaviour. • Future work, B(E2)s for 106,107Cd & 103,104Pd • (n,n’) work to get lower lying lifetimes in (stable) 106Cd, see talk by A. Linnemann

  33. Acknowledgements Royal Institute of Technology, Stockholm: K. Andgren Istanbul University: L. Amon R.B. Cakirli M.N. Erduran Uni. de São Pãulo: R.V. Ribas Yale University: E.A. McCutchan N.V. Zamfir R.F. Casten D.A. Meyer C. Plettner J. Vinson V. Werner E. Williams SUNY, Stony Brook: N. Pietralla G. Rainowski Clark University G. Gürdal • University of Surrey: • P.H. Regan • S.F. Ashley • N.J. Thomas • University of Paisley: • K.L. Keyes • Papenberg • CCLRC Daresbury: • D.D. Warner This work is supported by EPSRC (UK), U.S. Dept. Of Energy, under Grant No. DE-FG02-91ER-40609 and by the Yale University Flint and Science Development Fund

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