Nuclear Isomerism. Phil Walker. University of Surrey. on the occasion of the 70th birthday of Geirr Sletten

Size: px

Start display at page:

Download "Nuclear Isomerism. Phil Walker. University of Surrey. on the occasion of the 70th birthday of Geirr Sletten"

Rodger Clarke
6 years ago
Views:

1 Nuclear Isomerism Phil Walker University of Surrey on the occasion of the 70th birthday of Geirr Sletten

2 Nuclear Isomerism Phil Walker University of Surrey on the occasion of the 70th birthday of Geirr Sletten HAPPY BIRTHDAY GEIRR!!

3 What are isomers?

4 What are isomers? 1917: predicted by Soddy "different in their stability" 1921: uranium-x isomers observed by Hahn 1936: isomers explained as spin traps by von Weizsäcker excited nuclear states with long half-lives: > 1 ns

5 Why study isomers?

6 Why study isomers? At the limits of nuclear binding, isomers may be more stable than ground states.

7 Why study isomers? At the limits of nuclear binding, isomers may be more stable than ground states. 270 Ds α decay ms isomer at 1 MeV 0.1 ms ground state Hofmann et al., Eur. Phys. J. 10 (2001) 5 Xu et al., Phys. Rev. Lett. 92 (2004)

8 Why study isomers? At the limits of nuclear binding, isomers may be more stable than ground states. 270 Ds α decay ms isomer at 1 MeV 159 Re p decay µs isomer 0.1 ms ground state ground state unknown Hofmann et al., Eur. Phys. J. 10 (2001) 5 Xu et al., Phys. Rev. Lett. 92 (2004) Joss et al., Phys. Lett. B641 (2006) 34 Liu et al., Phys. Rev. C76 (2007)

9 Why study isomers? At the limits of nuclear binding, isomers may be more stable than ground states. KEY ROLE OF ANGULAR-MOMENTUM MAGNITUDE AND DIRECTION 270 Ds α decay ms isomer at 1 MeV 159 Re p decay µs isomer 0.1 ms ground state ground state unknown Hofmann et al., Eur. Phys. J. 10 (2001) 5 Xu et al., Phys. Rev. Lett. 92 (2004) Joss et al., Phys. Lett. B641 (2006) 34 Liu et al., Phys. Rev. C76 (2007)

10 A RECENT PHOTO

11 A USED TARGET

12 Chart of nuclides adapted from Lund web site

13 SLETTEN'S CHART

14 SLETTEN'S CHART

15 SLETTEN'S CHART

16 SLETTEN'S CHART

17 > 100 citations 1969

18 fission isomers 1969

19 1977 N ~ 82 isomers 16 NaI > 100 citations

20 1984 SATURN'S RINGS 14 NaI + 4 Ge(Li)

21 1984 SATURN'S RINGS 14 NaI + 4 Ge(Li)

22 1984 SATURN'S RINGS 14 NaI + 4 Ge(Li)

23 1985

24 10 NaI + 2 Ge(Li) (one suppressed) 1985

25 Os > 70 citations

26 1988 T 1/2 = 130 ns 6-quasiparticle isomer at 7 MeV bypassing 182-Os TESSA 3 (50 BGO + 12 Ge suppressed) with bunched beam of 36 S I beam current: on 5 ns off 200 ns time

27 counts gamma-ray coincidence spectrum 1988 bypassing ns 182-Os

28 isomer decay 1988

29 175-Hf 1990

30 9-quasiparticle isomer at 7.5 MeV ESSA 30 (30 Ge suppressed) recoil shadow τ > 10 ns 175 Hf 9-qp isomer 7455 kev bypassing 1990 bunched 48 Ca beam 7-qp 5-quasiparticle isomer at 3 MeV 3015 kev

31 175 Hf 175 Hf above 57/2 rotational bands based on 9-qp states Kondev et al., to be published Gammasphere 100 Ge suppressed "analysis of a number of high-seniority bands shows that they behave as if the nuclei rotate in the unpaired state" Frauendorf, Neergard, Sheikh, Walker, PRC61 (2000)

32 bypassing transitions nuclide K π bypassing quasiparticle intensity change 182 Os % Hf % Hf 57/2 >50 % W 35/2 95 % 5 1

33 bypassing transitions nuclide K π bypassing quasiparticle intensity change 182 Os % S 174 Hf % S 175 Hf 57/2 >50 % S 179 W 35/2 95 % S Do we understand the K-composition of S-bands? i.e. do we understand the orientation of the angular-momentum vector?

34 179-W 1983

35 W bypassing 14 NaI + 4 Ge(Li)

36 1983 bypassing 179-W

37 1983 bypassing 31/2 179-W

38 t-band K = 23/2 = bandhead spin W CAESAR: 6 Ge suppressed bunched and chopped beam Walker et al. PRL67 (1991) 433

39 W bands 174 W GAMMASPHERE bandhead? not an isomer K unknown [Tandel et al., Phys. Rev. C73 (2006) ]

40 174 W B(E2) ratios 2006 E2 transitions g s [Tandel et al., Phys. Rev. C73 (2006) ]

41 174 W B(E2) ratios 2007 K s = 8 ± 1 E2 transitions g s Walker, J. Phys. G34 (2007) 123

42 assume equal Q 0 s 2007 if K 1 = K 2, then c = 1, and R[B(E2)] s = R[B(E2)] g

43 174 W, K = 8 bandhead? 184 Os, K = 10 isomer bandhead 2007 full line: K = Ω <K s > 1 + Ω vs 2 for 2 i N 13/2 neutrons even-even nuclides K = Ω 1 Ω 2 Walker, J. Phys. G34 (2007) 123

44 174 W, K = 8 bandhead? 184 Os, K = 10 isomer bandhead 2007 full line: K = Ω <K s > 1 + Ω vs 2 for 2 i N 13/2 neutrons even-even nuclides high-k band crossings! K = Ω 1 Ω 2 Walker, J. Phys. G34 (2007) 123

45 Summary Types of isomerism: shape isomers, spin traps, K isomers Technical developments: recoil shadow, beam pulsing, detector arrays K-forbidden transitions: importance of t-bands

46 Summary Types of isomerism: shape isomers, spin traps, K isomers Technical developments: recoil shadow, beam pulsing, detector arrays K-forbidden transitions: importance of t-bands KEY ROLE OF ANGULAR-MOMENTUM MAGNITUDE AND DIRECTION

47 Summary Types of isomerism: shape isomers, spin traps, K isomers Technical developments: recoil shadow, beam pulsing, detector arrays K-forbidden transitions: importance of t-bands KEY ROLE OF ANGULAR-MOMENTUM MAGNITUDE AND DIRECTION Thank you, Geirr, for many years of friendship and physics!

48 KEY ROLE OF ANGULAR-MOMENTUM MAGNITUDE AND DIRECTION "what I tell you three times is true" from Lewis Carroll, The Hunting of the Snark

49 Saturn's rings!!

50 K values at bandcrossings Walker, J. Phys. G34 (2007) 123

51 quotes [Narimatsu et al., Nucl. Phys. A601 (1996) 69] for 172 Hf (N = 100) [Cullen et al., Nucl. Phys.A638 (1998) 662] for 174 W (N = 100) [Tandel et al., Phys. Rev. C73 (2006) ]

52 172 Hf yrast band I i = Q 0 (eb) [Cullen et al., Nucl. Phys.A638 (1998) 662] ħω (MeV)

53 172 Hf yrast band I i = Q 0 (eb) ħω (MeV) corrected for K = [Cullen et al., Nucl. Phys.A638 (1998) 662]

54 Jain odd-n systematics [Jain et al., Rev. Mod. Phys. 62 (1990) 393]

55 TIDAL WAVES 182-Os isomer rotation

and shape coexistence

Aspects University of nuclear of Surrey isomerism and shape coexistence - historical introduction - energy storage - enhanced stability - high-k isomers - neutron-rich A 190 isomers Phil Walker Isomer