Date post: | 13-Jul-2015 |
Category: |
Technology |
Upload: | brucelee55 |
View: | 563 times |
Download: | 6 times |
Nuclear Isomerism:Probes of Nuclear StructureandTools for the Future
Jennifer Jo ResslerWright Nuclear Structure Laboratory
Yale University
What is nuclear structure?
Nuclear structure is the study of nuclear excited states.
The pattern of excited states gives information on thenucleon-nucleon interaction, which we don’t understand.
atomic structure: study of atomic states created by electronic excitationsnuclear structure: study of nuclear states created by proton
and/or neutron excitations
atomic – nuclear comparisonAtomic
Can be described by a shell model, where electrons fill quantized energy levels.
Can be described by a shell model, where protons and neutrons separately fill quantized energy levels.
Nuclear
n, , m, s parity (-1) n, , m, s parity (-1)
Lowest energy levels have maximum S possible (due to Coulomb) with J = L + S = Σi + Σsi or J = Σji = Σ (i + si)
Lowest energy levels have minimum S possible due to strong force pairing with J = Σji = Σ (i + si)
Energy levels can be calculated by solving theSchrödinger equation using a central potentialdominated by the nuclear Coulomb field.
Energy levels are not easily calculated;nucleons move and interact within aself-created potential.
Spin-orbit coupling is weak Spin-orbit coupling is strongFor 3 electrons in a d orbital:
d3/2
d5/2
For 3 nucleons in a d orbital:
Why is the nucleon-nucleon interaction so hard to understand?
Nucleon forces do not vary with distance in a way that can be conveniently described by mathematical formulas!
Even if we could, each nucleon interacts with a few ofit’s neighbors with approximately equal forces –
many body problem
For electrons, consider each electron’s interaction withthe nucleus, then add other electrons as perturbations –
2-body problem
From the Periodic Chart to the Chart of Nuclides
AtPoBiPbTl
e−
Z
N
2, 8, 20,28, 50,82, 126, …
Magic numbers:
• Fundamental knowledge of the strong force• Formalisms of quantum mechanics (many body system)• Computational modeling and mathematics• Astrophysics• Nuclear medicine• Material science• Defense weapons (simulations)• Etc. (art, forensics, geology, … )
What use is nuclear structure?
Nuclear structure in a nut shell
• The nucleus is a bound system of protons and neutrons.• The nucleus exhibits different shapes and excitations.• Properties are understood on the basis of
single particle and collective motion.• Gamma-rays from the decay of an excited nucleus give information about the arrangement of quantum levels in a nuclear potential well, and the shape of the potential.• The arrangement of excited levels and shape delicately depend
on the nucleon number and angular momentum.
Gamma rays and energy levels
AZ N
X
Ji
Jf
Gamma ray: pure electromagnetic radiationchange in charge distribution: electric momentschange in current: magnetic moments
Emission of a gamma-ray removes Energy Angular momentum, L
one unit L = 1, dipole M1, E1two units L = 2, quadrupole M2, E2
parity: electric (-1)L magnetic (-1)L+1
Selection rule:
|Ji - Jf| ≤ L ≤ |Ji + Jf|
and 0 → 0 transitions are forbidden
only the lowest multipolarities are probable
coincidence
What is an isomer?
nuclear isomer: an excited state that does not decay within ~ps
isomers occur for:• large changes in nuclear spin (>2)
M2, M3, E4 …• small changes in energy• large changes in structure
Isomers decay by electron conversion, gamma emission, particle emission (p, α, β+, β-)
Near closed shells
“spherical structure” : potential is spherically symmetric
ΣH = T + V ( r )i i
A
i = 1
H = EΨ Ψi i i
each nucleon moves in an approximately spherical containing potential which represents the average interaction of each nucleon with all other nucleons
(near magic numbers)2, 8, 20,28, 50,82, 126, …
SphericalShell Model
(3p1/2)
(2f5/2)(3p3/2)
1i13/2
1h9/2
2f7/2
126
82
3p1/2
2f5/23p3/2
1i13/2
1h9/22f7/2
126
82π ν
114
210Ra
Spherical Shell Model
Spin-orbit splitting brings down high-j states close to low-j states –large change in spin => isomers
These isomers are evidence for the shell structure of nuclei.
2p3/21f5/22p1/2
1g9/22d5/21g7/23s1/22d3/21h11/22f7/21h9/21i13/23p3/22f5/23p1/2126
82
50
28
In 82 < N < 126 shell,
odd isotopes;
M213/2+ i13/2
9/2- h9/2
Spherical Shell Model
Coupling between nucleons may also create isomers:
h9/22
0+
2+
4+
6+8+
small change in energy => isomers
h9/2 ⊗ f7/2
h9/2 ⊗ i13/211-
8+
E2
E2
E2 E3
different structure => isomers
Non-spherical nuclei“deformed structure”: spherical symmetry is lostto a first approximation, potential is axially symmetric
β2 : measure of extent of deformationspherical β2 = 0large deformation β2 ~ 0.3 – 0.4
oblate (β2 < 0) spherical (β2 = 0) prolate (β2 > 0)
If β2 ~ ± 0.1, Spherical Shell Model states are still observed.
Deformed structures dominate when there are many valence nucleons – i.e. proton AND neutron numbers far from magic
Excited energy levels
even-even Pb isotopes
010002000300040005000
110 115 120 125 130 135
N
En
erg
y, k
eV
0+
2+
even-even Rn isotopes
0
500
1000
1500
110 115 120 125 130
N
En
erg
y, k
eV
0+
2+
“Spherical” nuclei:
First 2+ state in N=Z Nuclei
020040060080010001200
28 30 32 34 36 38 40 42 44 46
Z
En
erg
y, k
eV
2+
“Deformed” nuclei:
208Pb region
Ra
Rn
Po
Pb
Hg
210Ra
Pt
88
86
84
82
80
78126124122120118
211Ra209Ra
203Rn202Rn201Rn
116
Th90 212Th
208Ra
Z ~ 82, N ~126Near N = 126, Pt (Z=78) and Hg (Z=80) are nearly spherical – but at lower neutron numbers a deformed structureco-exists with the spherical.
-500
0
500
1000
1500
2000
2500
95 100 105 110 115 120
Pt experimental data0+2+4+6+8+0+2+4+6+8+
Ener
gy, k
eV
N
0
500
1000
1500
2000
2500
3000
90 95 100 105 110 115 120 125 130
Hg experimental data 0+2+4+6+8+0+2+4+6+8+
Ener
gy, k
eV
N
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
90 95 100 105 110 115 120 125
PtHgPbPoRnRa
β 2
N
Moller Nix Swiatecki FRDM
Z>820
500
1000
1500
2000
105 110 115 120 125 130
Po experimental data 0+0+2+2+4+4+6+8+
En
erg
y,
ke
V
N
0
500
1000
1500
2000
2500
110 115 120 125 130
Rn experimental data0+2+4+4+6+6+8+8+
Ene
rgy,
ke
VN
0
500
1000
1500
2000
110 115 120 125 130
Ra experimental data0+2+4+6+8+
Em
erg
y,
ke
V
N
0
100
200
300
400
500
600
700
800
100 105 110 115 120 125 130
Calculated and Experimental E(2+)
Po (calc)Po (exp)Rn (calc)Rn (exp)Ra (calc)Ra (exp)
Exc
itatio
n E
nerg
y, k
eV
N
particle emission
entry region
continuum statistical gamma rays
yrast line
Angular Momentum, I
Exc
itatio
n E
nerg
y
+
projectile target
compound nucleus
compound nucleus
Heavy-ion fusion evaporation reaction:π , ν , α
(3- 6 MeV/A)
How are nuclei produced?
• fusion evaporation reactions• deep inelastic reactions• fission fragments• projectile fragmentation
How do we measure γ-rays?Ge semiconductor
- when a γ-ray enters the detector, it disturbs the e- in the Ge crystal and the resulting pulse of charge is proportional to the initial energy of the gamma ray.
Germanium arrays: Gammasphere (LBNL) CLARION (ORNL) YRAST-Ball (WNSL)
YRAST-Ball Up to 13 clover detectors
9 at 90o
4 at 138.5o
2-4 LEPS Currently: 9 clovers and 2 LEPS … ε ≈
2.7%
ε ≈ 3.9%
YRAST-Ball: Yale-Rochester Arrayfor SpecTroscopy
SASSYER
M1QM2
beam dump
target area
carbon window
beam direction0
2 106
4 106
6 106
8 106
1 107
1.2 107
0
1000
2000
3000
4000
5000
6000
0 200 400 600 800 1000
background and contamination Rn x-rays 203Rn 202Rn
1x107
6x106
2x106
5x103
3x103
1x103
200 400 600 800 10000
0
2 1054 1056 10
58 10
51 106
1.2 106
400 450 500 550 600
4x105
8x105
1.2x106
400 500 600
a)
b)Cou
nts/
keV
Energy, keV
X
X
X
Small Angle Separator at Yale for Evaporation Residues
Target area detectors:• YRAST Ball•NYPD• Rutherford detectors• BGO calorimeter• ICEY Ball
Wright Nuclear Structure Laboratory, Yale University
Focal plane detector systems:• Solar cell array • Ge detectors … isomer array• Position sensitive PPAC’s• Silicon-strip detector• MTC, β-decay tagging system• CdZnTe array
SASSYER
delayed γ-rays
τ
prompt γ-rays
Dual study: prompt and delayed
Isomer Decay Tagging
Recoil TOF ~ 800 ns
30Si (148 MeV) + 184W → 210Ra + 4n
Prompt γ-ray spectra
0
2000
4000
6000
8000
1 104
1.2 104
1.4 104
0 200 400 600 800 1000
Cou
nts/
keV
Energy , keV
0
1000
2000
3000
4000
5000
200 300 400 500 600 700 800 900
Cou
nts/
keV
Energy , keV
209,210,211Ra
Ra x-rays
Delayed γ-ray spectra
210Ra
210Ra0+
4+4+
6+8+t1/2 = 1.7(2) µs
0
50
100
150
200
250
300
350
400
0 200 400 600 800 1000
Cou
nts/
keV
Energy, keV
2+
750
600
603
773
577
0
50
100
150
200
560 580 600 620 640Energy, keV
Cou
nts
/0.5
keV
10coun
ts
54321time (µs)
1.7(2) µs
Correlated spectra
0
50
100
150
200
250
320 400 480 560 640 720 800 880
Cou
nts/
keV
Energy, keV
210Ra0+
4+4+
6+8+ t1/2
2+
750
600
603
773
5770
20
40
60
80
100
120
100 200 300 400 500 600 700 800
Cou
nts/
keV
Energy, keV
Ra x-rays
10+
11-1112-
12,13
518232 307
218635
688
tentative!
4+ feeding
50
60
70
80
90
100
200 400 600 800
Cou
nts
Energy, keV
210Ra0+
4+4+
6+8+t1/2 = 1.7(2) µs
2+
750
600
603
773
577
prompt γ-ray spectrum
Comparisons to isotones
Ener
gy, M
eV
1.0
2.0
3.0
0.0 0+ 0+ 0+
2+2+2+
2+4+ 4+
4+
4+4+4+
6+8+ 6+
8+ 6+8+
10+
11-
10+
11-
10+
11-
206Po 208Rn 210Ra
473 ns1.7 µs
212 ns
πh9/22
Comparisons to isotopes
0+
2+4+6+8+8+
11-10+
12+14+
17+
12+
0+
2+
4+
6+8+8+10+11-
1213-
16+
0+
2+
4+4+
6+8+10+1111-12-12,13
0
1.0
2.0
3.0
4.0
Ener
gy, M
eV
210Ra 212Ra 214Ra
67 µs11 µs1.7 µs
333 ns
285 ns
230 ns
850 ns
6 protons above Z=82;h9/2
6 h9/22 0+, … 8+
2+(h9/22) 10+, ..
h9/2f7/2 8+
h9/2i13/2 11-
8+ isomer half-life
1.7 µs
473 ns
212 ns
10.9 µs 67 µs
126124122
88
86
84
210Ra 212Ra 214Ra
208Rn
206Po
↑ t1/2 increases
← t1/2 decreasesMore neutron degreesof freedom – lowspin states are not‘pure’ πh9/2
2
More proton degreesof freedom – 8+ ofπh9/2
2 mixes withπh9/2 x πff/2
(3p1/2)(2f5/2)(3p3/2)1i13/2
1h9/2
2f7/2
126
82
3p1/2
2f5/23p3/2
1i13/2
1h9/22f7/2
126
82π ν
114
644 ns 910 ns
210Rn 212Rn
350 ns 99 ns
208Po 210Po
Are there other isomers?
Probably.206Po : 9- (νi13/2 x νf5/2) 1.0 µs
10+
9-
8+
(3p1/2)
(2f5/2)(3p3/2)
1i13/2
1h9/2
2f7/2
126
82
3p1/2
2f5/23p3/2
1i13/2
1h9/22f7/2
126
82π ν
114
πh9/22
isomers in Po and Rn11- (πh9/2 x πi13/2)
Neutron-rich nuclei
N
Z
N=Z
large neutron excess – magic numbers no longer magic!
New shell structure –what are the new magic numbers?
Radioactive Ion Beams – (RIA?)
Isomers are excellent probes!
Far from closed shells
I
J
R
j
s
KΩ
Λsymmetry axis
Rotational bands: E α I(I+1)
I = K
I + 2
I + 4
I + 6
I + 8I + 9
I + 7
I + 5
I + 3
I + 1
M1’s
E2’s
Band comprised of two signature partners for even-A (even Z-even N or odd Z-odd N nuclei) favored I = 0, 2, 4, 6 ... unfavored I = 1, 3, 5, 7 ... for odd-A (even Z-odd N or odd Z-even N nuclei) favored I = 1/2, 5/2, 9/2, 13/2 ... unfavored I = 3/2, 7/2, 11/2, 15/2 ...
collective motion =>
I = J + R
rotational bands
E =(1/2I)[ I(I+1) – K2]
Nilsson model
Oblate β2 < 0
Spherical β2 = 0
Prolate β2 > 0
g9/2
9/2
7/2
5/2
3/2
1/2
1/2
3/2
5/2
7/2
9/2
[404]
[413]
[422]
[431]
[440]
[N nz Λ ]ž ž
50
28
40
g9/2
d5/2
p1/2
f5/2
p3/2
f7/2
38
3434
36
[303]7/2
[312]5/2
[321]3/2
[321]1/2[310]1/2
[312]3/2[440]1/2
[431]3/2
[422]5/2
[404]9/2
[413]7/2
[301]3/2[303]5
/2[301]1/2
-0.3 -0.2 -0.1 0.0 +0.1 +0.2 +0.3 +0.4
β2
Rel
ativ
e E
nerg
y
[431]1/2
Nilsson diagram:
ΩΩ
K = Ω1 + Ω2 …
Deformed odd-massA~80 nuclei dominatedby [422]5/2+ and [301]3/2-
configurations:
Z = 39 N = 3979Y 5/2+ 77Sr 5/2+
81Y 5/2+, 3/2- 113 keV
Z = 41 N = 4183Nb 5/2+ 81Zr 3/2-, 5/2+ X keV
79Sr 3/2-, 5/2+ 177 keV
β2 prolate deformation
[404]9/2
[301]3/2
[422]5/2
[440]1/2
[431]3/2
[431]1/2
[413]7/2
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Rel
ativ
e E
nerg
y (M
eV)
0.0
2.0
4.0
6.0
40
38
50
28
[312]3/2
[303]7/2[310]1/2
[303]5/2[301]1/2
[550]1/2g
9/2
p1/2
f5/2
p1/2
Nilsson diagram for A- 80 :
80Y:Z = 39, N = 41
What happens if we combine a deformed odd-proton and odd-neutron?
Gallagher-Moszkowski rules:K = Ωp + Ωn if Ωp = Λp ± ½ and Ωn = Λn ± ½K = |Ωp - Ωn| if Ωp = Λp ± ½ and Ωn = Λn ± ½
±
For π[422]5/2+ ⊗ ν[301]3/2- expect 4- ground state, 1- excited state
4-
1- K = 1
K = 4
80Y rotational bands
D. Bucurescu et al., Z. Phys. A 352, 361 (1995).
80Y isomers
4.7 s isomer19% beta decay81% gamma decay (229 keV)suggested to be M31- 4- decay to ground state
M3 nature confirmed
4.7 µs isomergamma decay (83 keV)suggested to be E1
π [422]5/2+ ⊗ ν [301]3/2 -
4-
1-
J. Döring, H. Schatz, A. Aprahamian et al., PRC 57, 1159 (1998).
A. Piechaczek, E. F. Zganjar et al., PRC 61, 047306 (2000).
C. Chandler, P. H. Regan et al., PRC 61, 044309 (2000).
80Zr beta decay
Beta decay: Gamow-Teller
3+
4-83 keVE14.7 µs 2+
1-83 keVE14.7 µs
80Zr 0+
β+/EC
E2
1+
80Zr 0+
β+/EC
M1
1+
Either scenario feeds the µs isomer…
rp-process nucleosynthesis
Ge
As
Se
Br
Kr
Rb
Sr
Y
ZrNb
Mo
Tc
Ag
32 34 36 38 40 42 44
46
48 50
52 54
Ru
Rh
Pd
Cd
In
Sn
30
H. Schatz et al., Phys. Rep. 294, 167 (1998).X-ray burst > 10% reaction flow
P
P P
P
P
P
P
Neutron Star
Donor Star(“normal” star)
Accretion Disk
The ModelNeutron stars:1.4 Mo, 10 km radius(average density: ~ 1014 g/cm3)
Typical systems:• accretion rate 10-8/10-10 Mo/yr (0.5-50 kg/s/cm2)• orbital periods 0.01-100 days• orbital separations 0.001-1 AU’s
X-ray burst From H. Schatz, MSU
Astrophysical implications of 80Zr t1/2
S
Nb
Zr
Y
Sr
Rb
Kr
X
40 41 42 43 44
6.85 s
X-ray burst coolswhile 80Zr decays;proton capture on80Y becomes moredifficult.
80Zr set-up
RMS
MTC195 MeV 58Ni on 500 µg/cm2 24Mg
Oak Ridge National Laboratory
0+80Zr
83 keV
β+/EC
4.7 µs1+
80Y
RMS: Recoil Mass Spectrometer
Oak Ridge National Laboratory, Holifield Heavy Ion Research Facility
Recoil Mass Spectrometer
Momentum Separator (P/Q)
Mass Separator (A/Q)
Fo
ca
l Pla
ne
Q1
Q2
D1
S1
Q3
S2
D2
Q4Q5
ED1
D3
ED2Q6 Q7
“M/Q separator” or“mass separator”
10
0 5 10 15 20
Zr
deca
ys/ 0
.5 s
Time (s)
5
80Zr half-life
TAC:Start: scintillator (β)Stop: LOAX (low energy γ)
80Zr t1/2: 4.1(8) s
J. J. Ressler, W. B. Walters, M. Wiescher, A. Aprahamian, et al. Phys. Rev. Lett. 84, 2104 (00).
80Zr
83 keV
β+/EC
4.7 µs1+
80Y
Astrophysical implications of 80Zr t1/2
S
Nb
Zr
Y
Sr
Rb
Kr
X
40 41 42 43 44
4.1 s
X-ray burst remains warmwhile 80Zr decays; protoncapture on 80Y becomespossible.
Does 1- beta decaying isomer play a role?
IDT experiment set-up
85 MeV 28Si on 300 µg/cm2 54FeOak Ridge National Laboratory
RMS
delayed γ-rayprompt γ-rays
Isomer Decay Tagging83 keV
Recoil TOF ~ 3.5 µs
t1/2 = 4.7 µs
CLARION: Clover Array for Radioactive ION beams
11 clovers :~ 2.5% efficiency for 1.3 MeV γ-rays
5 at 90o
4 at 132o
2 at 155o
IDT results0
5000
1 104
1.5 104
0 50 100 150 200 250 300 350
0
50
100
150
200
250
0 50 100 150 200 250 300 350
-10
0
10
20
30
40
50
60
70
0 50 100 150 200 250 300 350
80Y (pn)
80Sr (2p)
79Sr (2pn)
79Rb (3p)
Energy, keV
Co
un
ts
3 x 104
0 1000
0 1000
0 1000
500
50
25
1000
6 x 1041.5 x 104
1.0 x 104
a)
b)
c)143
193
289
238
299334
2500
2000
1500
1000
500
0500
400
300
200
100
0
2500
2000
1000
100 200 300 400 500
1500
500
Cou
nts
Energy, keV
83; 80Y
511; γ−γ
175; 80Rb
78; 80Rb
J. J. Ressler et al., PRC 63, 067303 (01).
338
538
731
951
1004
814
624
431
853
590
289
527
43
6
143193
238300
324
407
407
544
2
1030
778
314
83 keV
40
20
0
500 1000
Cou
nts
Energy, keV
143
193
238
289 300314
324
338 431 527538 589 624 814
9511004 1030
778
E* = 312 keV
But why is this state isomeric?
2+
1-83 keVE14.7 µs
4-M3 229 keV
4.7 s
143
193
238
299
324 731
537
336
431
623
(4+)
(6+)
(5+)
(3+)
(7+)
β2 prolate deformation
[404]9/2
[301]3/2
[422]5/2
[440]1/2
[431]3/2
[431]1/2
[413]7/2
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Rel
ativ
e E
nerg
y (M
eV)
0.0
2.0
4.0
6.0
40
38
50
28
[312]3/2
[303]7/2[310]1/2
[303]5/2[301]1/2
[550]1/2g
9/2
p1/2
f5/2
p1/2
Nilsson diagram for A 80 :
2+:π [422]5/2+ ⊗ ν [431]1/2+
Compare with N=4179Sr ½+ band : similar moment of inertia – very deformed
=> 2+ state may be a shape isomer
1- is not ‘pure’ : [413]7/2+ ⊗ [303]5/2-, [422]5/2+ ⊗ [312]3/2-, [431]3/2+ ⊗ [301]3/2-, [431]3/2+ ⊗ [303]5/2-, [431]1/2+ ⊗ [301]3/2-
K-isomers
low-K
high-K
Expect K-isomers in regions wherehigh-Ω orbitals of deformed nuclei are near the Fermi surface
178HfK = 00+
K = 88+
K = 1616+
0
1.1 MeV
2.4 MeV
64% ν[514]7/2- x ν[624]9/2+
36% π[404]7/2+ x π[514]9/2-
ν[514]7/2- x ν[624]9/2+
x π[404]7/2+ x π[514]9/2-
4-qp
2-qp
K-isomers
Z = 74, N = 104 Ta/Hf region A ~ 180near stabilitylong-lived isomers (sec – years)
Z = 66, N = 104 Dy, A ~ 170neutron driplineunstable beams
Z = 66, N = 74 A ~ 130, 140proton driplineµs isomers – IDT
Heavy elements – No (Z = 102) and Z=110 have been reported
A~170-190
YbLuHfTaWReOs
Z=74
100 105 110
proton rich
neutron rich
Need:unstable beams (N>Z) oralternative production mode(not fusion evaporation)
Non-structure interestsAstrophysics: most elements are produced in neutron-capture processes
s-process : proceeds via successive neutron captures and beta decays
slow neutron capture rate;Rcapture << Rbeta
r-process : proceeds via successive neutron captures and beta decays
fast neutron capture rate;Rcapture > Rbeta
Hf
Lu
Yb 104 105 106176Lu
1-
7-
3.7 hours
4 x 1010 years
Non-structure interests
Potential energy source: controlled triggering of isomer decay
178Hf
2.4 MeV, t½ = 31 years 40 ± 20 keV
observed: Phys. Rev. Lett. 82, 695 (1999).refuted: Phys. Rev. Lett. 87, 072503 (2001).
γ-ray lasers: 43,44,45,46Sc, 58Co, 57Fe, 63Ni, 65,67Zn, 74Ga, 69,73,75,77Ge, 76As, 77,79Se, 77,79,83Kr, 83Rb,90,92Nb, 99Mo, 105Ru, 100,105Rh, 107Pd, 103,107,109,110,111,116,118,120Ag, 116,119In, 109Cd, 115Sn,118,120,122,126Sb, 120,122I, 125Xe, 134,140Cs, 137,138La, 140Nd, 141,152,154Eu, 153,157Gd, 157,169,171Er,165,167Tm, 172,173,177Lu, 173,175Hf, 177,181,183Ta, 179,180Re, 181Os, 187Pt, 189Au, 207,209,210Po,206Bi, 243Cm
Bio-engines??
Chart of Nuclides
N
Z Neutron rich nuclei: very l i t t le known!
Exotic proton rich nuclei
Summary of isomer studies presented
Spherical – 210Raprobe: spherical structuretool: correlate states across the µs-isomer
Deformed – 80Yprobe: deformed structuretool: 80Zr beta decay
and to correlate states across the µs-isomer
Understanding why certain states are isomeric is important!
THANKS!
Is a recoil/mass separator necessary?
Not always –beam
YRASTBall and target chamber
90Zr foil and BGO detectors
0
100
200
300
400
200 280 360 440 520
delayedprompt*.00075
counts
/keV
Energy (keV)
84Nb
Other techniques
a) thick target experiments -- recoil is stopped
-- short-lived (ns) isomers
b) beam pulsing-- beam on/off regularly-- short-lived isomers
c) Moving tape collector
d) fission => isomers
beamtarget
Comparisons to isotopes
0+
2+4+6+8+8+
11-10+
12+14+
17+
12+
0+
2+
4+
6+8+8+10+11-
1213-
16+
0+
2+
2+4+4+
6+8+10+1111-12-12,13
0
1.0
2.0
3.0
4.0
Ener
gy, M
eV
210Ra 212Ra 214Ra
67 µs11 µs2.2 µs
333 ns
285 ns
230 ns
850 ns
6 protons above Z=82;h9/2
6 h9/22 0+, … 8+
2+(h9/22) 10+, ..
h9/2f7/2 8+
h9/2i13/2 11-
Temp
3
2
1
0
ln(c
ount
s)
7000600050004000300020001000time (ns)
t1/2 = 456