1. Future Challenges Using Decay Spectroscopy with Projectile Fragmentation and In-Beam Deep Inelastic Reactions
Paddy Regan
Dept. of Physics
University of Surrey,UK

2. Outline of Talk (Some) Physics questions in heavy neutron-rich nuclei.
Thin target multinucleon transfer reactions:
100Mo+136Xe : reaction mechanism info.
198Pt+136Xe: 136Ba Ip=10+seniority isomers, effective charges.
Projectile-fragmentation isomer spectroscopy.
The Stopped Beam RISING Campaign, some physics aims.
g-factors and BaF2 timing below isomers.

3. Main physics interest in neutron-rich nuclei is based on the
EVOLUTION OF SHELL STRUCTURE and the appearance of
‘large gaps in the nuclear single-particle spectrum’.
Reasons to study neutron-rich nuclei
Evolution of collective modes (vibrations, rotations, superdef ?)
from spherical states by altering (N,Z,Ip, Ex).
2) Identification of specific nucleonic orbitals, e.g. via isomeric
decays, g-factors, B(E2:I->I-2), effective charges, shell model
descriptions, seniority schemes, deformed (Nilsson) schemes etc.
3) Identifying new nuclear ‘exotica’, e.g., the unexpected,
beta-decaying high-spin states, new symmetries (e.g., a32),
neutron ‘skins’, new shell closures, shape changes etc.

4. How do we study the heavy neutron-rich ?
Multi-nucleon transfer reactions:
Backed/thick target technique (made famous by Broda, Fornal,
Krolas (Crakow group) + Daly, Janssens, Khoo, Lunardi et al.,)
Projectile-fragmentation reactions:
Isomer spectroscopy (made famous by Pfützner, Rykaczewski, Grzywacz, Janas, Lewitowicz et al., & the Warsaw Group).
In both cases, the reaction mechanism is not fully
studied and experiments are needed in order to
set the limits of both of these techniques.

5. Aim? To perform high-spin physics in stable and neutron rich nuclei.
Problem: Fusion makes proton-rich nuclei.
Solutions? (a)fragmentation (b) binary collisions/multi-nucleon transfer
Modified from Introductory Nuclear Physics, Hodgson, Gadioli and Gadioli Erba, Oxford Press (2000) p509
See eg.
Broda et al. Phys. Rev Lett. 74 (1995) p868
Juutinen et al. Phys. Lett. 386B (1996) p80
Wheldon et al. Phys. Lett. 425B (1998) p239
Cocks et al. J. Phys. G26 (2000) p23
Krolas et al. Acta. Phys. Pol. B27 (1996) p493
Asztalos et al. Phys. Rev. C60 (1999)

6. z x q2 q1 f1 f2 y

7. BLF
TLF
beam
qtlf,ftlf
qblf,fblf Ge
Simon et al., Nucl. Inst. Meth. A452, 205 (2000)
Rochester Group
TOF ~5-10 ns.
ns-ms isomers can
de-excite in be
stopped by CHICO
position detector. Delayed
gs can still be viewed
by GAMMASPHERE.

8. 100Mo + 136Xe @ 700 MeV GAMMASPHERE + CHICO
PHR, A.D. Yamamoto et al., AIP Conf. Proc. 701 (2004) p329

9. Can we use the data from the CHICO+Gammasphere expt.
to understand the ‘DIC’ reaction mechanism ?
A wide range of spins & nuclei are observed.

10. R.Broda et al., Phys. Rev. C49 (1994)

11. Wilczynski (‘Q-value loss) Plot
A.D.Yamamoto,
Surrey PhD thesis (2004)
Wilczynski (‘Q-value loss) Plot

12. Gating on angle
gives a dramatic
channel selection in
terms of population.
Relative Intensities
of 6+->4+ yrast
transitions in
TLFs (relative to
100Mo) for 136Xe
beam on 100Mo
target at
GAMMASPHERE
+ CHICO.

13. Fold distributions highlight different reaction mechanisms
+2p
-2n
+2n
PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003)

14. Emission angle of TLFs can give information/selection
on reaction mechanism (and maybe spins input ?)

16. 198Pt +136Xe, 850 MeV
J.J. Valiente-Dobon, PHR,
C.Wheldon et al., Phys. Rev.
C69 (2004)

17. nano and microsecond isomers on gated 198Pt+136Xe with
J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004)
nano and microsecond isomers
on gated 198Pt+136Xe with
GAMMASPHERE+CHICO
DIC 84 83 82 81 80 79 78 77 76 75 74 73 59 58 57 56 55 54 53 52 51 50
N/Z compound

18. J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313
136Xe+198Pt reaction beam-like fragment isomers.
131I
133I
128Te
130Te
136Xe
132Xe
138Ba
137La

19. J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313
136Xe+198Pt Target-like fragment isomers
184W
195Os
192Pt
185Re
191Os
198Pt
193Au
192Os

20. Identification of new ‘seniority’ isomer in 136Ba, N=80 isotone.
T1/2=91(2) ns
J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004)

21. N=80 isotonic chain, 10+ isomers, (nh11/2)-2I=10+
Q. Why does Ex(10+) increase while
E(2+) decreases ?
91(2) ns

22. Structure of 8+ final state changes from 134Xe -> 136Ba ?
See Valiente-Dobon, PHR, Wheldon et al., PRC69 (2004)
Isomer decay
also depends
on structure
of final state
N=80, (nh11/2)-210+ isomers

23. Energy of N=80
Ip=10+ isomers
correlates with
energy increase
of 11/2- single
neutron in
N=81 isotones.
Increase in 10+
energy, plus
expansion of
proton valence
space means
8+ yrast state
now (mostly)
NOT (nh11/2)-2
for Z>54
Ex, Ip=11/2 -
N=81
Ex, Ip=10
N=80

25. Pair Truncated Shell Model
Calculations (by Yoshinaga,
Higashiyama et al. Saitama)
predict yrast 8+ in 136Ba
no longer mostly (nh11/2)-2
but rather, (pd5/2)2(pg7/2)2

26. Expect neutron ‘seniority scheme’
for (nh11/2)-2 ‘j2’ mutliplet
configuration at N=80 (e.g. 130Sn).
132Te, 134Xe have proton excitations
due to g7/2, d5/2 at 0+,2+,4+,6+ but
not competing 8ħ and 10ħ states.
Extra collectivity for higher-Z pushes down 0+ and 2+.
Proton s.p. energies
used in 136Ba SM calcs
h11/2
2.760
Protons, max. seniority 2
spin = 6 ħ (from (pg7/2)2.
Seniority 4 states though
can have up to
7/2 + 5/2 + 5/2 +3/2 = 10 ħ
d5/2
0.963
g7/2
0.000

27. Use FRS@GSI or LISE3@GANIL to ID nuclei.
In-Flight Technique Using Projectile Fragmentation
Production target
Central focus, S2
Final focus, S4
primary beam
1GeV/u
dipole, Br
degrader
degrader
MW=x,y
scint
scint
catcher
DE(Z2)
scint
(veto)
Use or to ID nuclei.
Transport some in isomeric states (TOF~ x00ns).
Stop and correlate isomeric decays with nuclei id.
eg. R. Grzywacz et al. Phys. Rev. C55 (1997) p1126 -> LISE
C.Chandler et al. Phys. Rev. C61 (2000) > LISE
M. Pfützner et al. Phys. Lett. B444 (1998) p32 -> FRS
Zs. Podolyak et al. Phys. Lett. B491 (2000) p225 -> FRS
M. Pfützner et al. Phys Rev. C65 (2002) > FRS

28. 8+ isomer in 78Zn,
real evidence of
78Ni shell closure.
J.M.Daugas et al.
Phys. Lett.
B476 (2000) p213

29. Heaviest odd-odd,N=Z gammas, isobaric analog states. 86Tc, C
Heaviest odd-odd,N=Z gammas, isobaric analog states ? 86Tc, C. Chandler et al. Phys. Rev. C61 (2000)
Can perform
spectroscopy at
rates of few ions
per hour.

31. M. Mineva et al. Eur. Phys. J. A11 (2001) 9
Use FRS to select projectile fission products (forward boosted ones). Note transmission a few %.
T1/2=565(50) ns state in 136Sb (Z=51, N=85)
135Te
136Sb

32. Prompt ‘flash’ is a limiting
problem for isomer
Fragmentation.
Reduces effective Ge
efficiency by factor of 3-4 !
(Partial) Solution ?
Use a low-Z (e.g., plastic stopper)

33. Simulated by
P. Detistov Surrey/Sofia

34. M.Pfutzner,M.Hellstrom et al.

35. 208Pb region 217Ac, 29/2+, 1μs 215Ra, 43/2-, 800ns 212Po, 18+, 65s
many μs isomers
expected
N=126, holes in 208Pb

36. (pg9/2)-2 ‘2j’ multiplet
(and isomer) in
130Cd (Z=48, N=82)
should look like
98Cd (Z=48, N=50)
A real test of valence
anaolgue scheme.
Do with fission fragments.
(pg9/2)-2

37. Doubly-mid-shell nucleus, 170Dy N=104, Z=66 (Np.Nn=352=Maximum!).
Best K-isomer?
Doubly-mid-shell nucleus, 170Dy
N=104, Z=66 (Np.Nn=352=Maximum!).
Appears to be a correlation between
fn values and NpNn for K=6+ isomers
in A~180 region.
(see PHR, Oi, Walker, Stevenson & Rath,
Phys. Rev. C65 (2002) )
Extrapolation suggests
isomer in 170Dy lives for
hours….could be
beta-decay candidate.
170Dy ?
N=104 isotones,
K=6+ energy
172Hf, 174Yb, 174Hf, 176Hf, 178Hf, 178W K=6+ isomers
Xu, Regan, Walker et al

38. First id of ‘doubly mid-shell’
nucleus, 170Dy (N=104, Z=66).
Data from M.Caamano et al.
33 ns isomer in 195Os (last stable 192Os), useful test of structure in prolate/oblate shape coexistence region. 194Os Wheldon et al. Phys. Rev. C63 (2001) (R)

39. BaF2 ‘fast timing’ data from H. Mach et al. Contribution to ENAM 2001
Allows an ordering of the gammas under isomer from their (~ps) lifetimes.

40. From Henryk Mach et al., 96Pd.

41. Use (BaF2,BaF2) coincidences below isomers to get B(E2) values
( & order gamma-transitions)
96Pd H. Mach et al.,

43. g-factors from fragmentation isomers
Basic idea, put isomer in B-field. Perturbation of gamma-ray angular distribution depends on induced Torque.
Rate of precession gives Larmor frequency, which gives g-factor.
‘Wiggles’ in count ratio between different angles from 13/2+ isomer, T1/2= 354(2)ns in 69Cu.
G.Georgiev EPJA20 (2004) p93;
J. Phys. G28 (2003) p2993
See poster by Steve Mallion

44. 50 delegates, ~ 20 presentations, 4 working groups…..
Stopped Beam Physics Workshop, Guildford 29-30th March 2004

45. Major campaign using ‘retired euroball’ detectors
for fragmentation-based nuclear
spectroscopy.
Stopped-Beam Campaign to
study decays from isomers and
following beta-decay.
First call for proposals (deadline was last week),
three proposals initially submitted for ‘isomer only’ study
1) A~110 neutron-rich Zr,Mo,Ru,Pd (Alison Bruce)
2) A~140 proton drip-line, proton decay daughters (Dave Cullen)
3) N=126, ‘south’ of 208Pb (Zsolt Podolyak)
+ g-factor letter of intent (Gerda Neyens)
‘Active stopper’ experiment planned for next EA (170Dy, 130Cd, etc.)

46. International Conference On NUclear STructure, Astrophysics &
Reactions University of Surrey,
Guildford, UK 5-8 January 2005

47. Happy Birthday Rafal !!

48. PHR, Valiente-Dobon, Wheldon et al., Laser Phys Letts. 1 (2004) 317

49. Crossing and alignments well reproduced by CSM, although AHVs

50. Smith, Walker et al., Phys. Rev.
C68 (2003)

52. Kinematics and angular mom
Kinematics and angular mom. input calcs (assumes ‘rolling mode’) for 136Xe beam on 100Mo target.
Estimate ~ 25hbar in TLF
for ~25% above Coul. barrier.
For Eb(136Xe)~750 MeV, in lab
qblf~30o and qtlf~50o.
100Mo +136Xe (beam)
DIC calcs.

53. Gamma-gamma analysis on 200Pt isomer (21 ns. ), M. Caamano et al. Nucl
Gamma-gamma analysis on 200Pt isomer (21 ns!), M. Caamano et al. Nucl. Phys. A682 (2001) p223c; Acta Phys. Pol. B32 (2001) p763 stripping effect to extend lifetime

54. “Power” of fragmentation
Z. Podolyak et al.,
“Power” of fragmentation
Low spin
~1 ms
PROTON RICH
I=43/2

55. 76Rb
69Se
67Ge
Chandler et al. Phys. Rev. C61 (2000)

56. (Stable beam) fusion limit makes high-K in neutron
Search for long (>100ms) K-isomers in neutron-rich(ish) A~180 nuclei.
low-K
high-K
mid-K j K
Walker and Dracoulis
Nature 399 (1999) p35
(Stable beam) fusion limit
makes high-K in neutron
rich hard to synthesise
N=104 also a
good number
for K-isomers.

57. Prompt flash knocks out a large portion of the detectors…
Prompt flash knocks out a large portion of the detectors….effectively reduces the gamma efficiency by upto 80%! Need digital electronics and time stamping

58. M. de Jong et al. Nucl. Phys. A613 (1997) p435
M. Pfutzner et al. Phys Rev. C65, (2002)

59. Isomeric Ratio Calculations
M. Pfutzner et al.
Phys Rev. C65, (2002)

60. Pfutzner, Hellstrom, Mineva et al.

62. PHR, Beausang, Zamfir, Casten, Zhang et al. , Phys. Rev. Lett

64. BUT….what is the microscopic basis ?
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)

65. 50 82
[550]1/2-
1h11/2
1g9/2
[541]3/2-

66. See PHR, Yamamoto, Beausang, Zamfir, Casten, Zhang et al.,
AIP Conf. Proc. 656 (2002) p422
‘Weak Coupling’
Eg/(I-j) E-GOS
extension for odd-A
Suggests 11/2- band
is anharmonic,
g-soft rotor?
BUT
seems to work ok
for +ve parity bands
vib ->rotor following
(nh11/2)2 crossing.

67. What about odd-A nuclei….are the nh11/2 bands ‘rotational’ ?

69. Carl Wheldon (HMI-Berlin) has suggested extension of E-GOS
by ‘renormalising’ the rotational energies at the bandhead.
If the band-head spin of a sequence is given by j then
substituting I-j in place of I, one obtains,

70. PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313
Can see clearly to spins of 20ħ using thin-target technique.

71. Even-Even yrast sequences and odd-A +ve parity
only show rotational behaviour after (nh11/2 )2 crossing….
seems to work ok, nh11/2 bands now look like rotors,

72. 215Ra τ = 800 ns, 43/2-, 3.8 MeV 407 keV γ-ray from 206Pb(13C,4n)
Stuchbery et al.
Nucl. Phys. A641 (1998) 401

73. 215Ra γ-ray spectrum from 238U fragmentation
Z. Podolyak, private communication
from 238U fragmentation

74. Abrasion-ablation model
(1-2/3)
k = A>10
De Jong, Ignatyuk, Schmidt, NP A613 (1997) 435.
“sharp cut-off” approximation:

75. 179W populated in:
fragmentation of 208Pb at 1 GeV/u
fusion evaporation: 170Er(13C,4n) at 67 MeV

76. Higher spins for greater DA.
M. Pfutzner, PHR et al. Phys Rev. C65, (2002)
Higher spins for greater DA.

77. High spins (>35/2) populated
208Pb beam at 1 GeV/u allows production of ( high-spin isomers,
M. Pfützner et al. Phys Rev. C65 (2002)
High spins (>35/2) populated

78. Projectile Fragmentation Reactions
hotspot
Excited
pre-fragment
Final
fragment
projectile
target
Energy (velocity) of beam > Fermi velocity inside nucleus ~30 MeV/u
Can ‘shear off’ different combinations of protons and neutrons.
Large variety of exotic nuclear species created, all at forward angles
with ~beam velocity.
Some of these final fragments can get trapped in isomeric states.
Problem 1: Isotopic identification. Problem 2: Isomeric identification.

79. PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313
TLFs
BLFs
elastics

80. Can see 184-194Os in binary partner channels. i.e.in 2p transfer,
up to 14 neutrons evaporated. ( 4n -> 194Os is heaviest known).

81. J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313
198Pt, 2+
136Xe, 2+

82. J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313
138Ce
125Sb

83. Super-FRS yields
215Ra

84. 170Dy, double mid-shell, ‘purest’ K-isomer ?
(see PHR, Oi, Walker, Stevenson and Rath,
Phys. Rev. C65 (2002) )
Kp=6+state
favoured
Max at 170Dy