High Spin Isomers: what we can learn
from
laser spectroscopy
stable
isotopes
nuclear
ground
states
Paul
Campbell
isomer only
off-line spectroscopy
(Kluge & Noerterhauser)
Ground State Properties
Isotope Shift (IS)
Mean Square Charge Radii
δ r
′
2 AA
Hyperfine Structure (HFS)
Nuclear Spin I
Magnetic Dipole Moment µI
Electric Quadrupole Moment Qs
Hyperfine Anomaly
Charge radii affected by size, shape,
rigidity and diffuseness….
High spin isomers
(spin-aligned isomers)
Optical Data
<r 2 > evaluation is model
independent and provides a
sensitive probe of the nuclear
shape and size
Deformed shape
Quadrupole deformation
Nuclear diffuseness
Neutron number
Hafnium charge radii
0.2
β2 = 0.3
Isomer measurement;
Boos et al.
Dubna, Orsay, Mainz,
McGill
PRL 72 (1994) 2689
-0.2
2
2
<r > (fm )
0.0
-0.4
β 2 = 0.2
-0.6
-0.8
166 168 170 172 174 176 178 180 182 184 186
Atomic Mass Number
The isomer has a static
quadrupole moment that
is greater than the static
+ dynamic quadrupole
moment of the gs
targets
beam
208
Bi
10
206
Bi
%
202
Tl
1
The IGISOL
facility, JYFL
180
W
201
Tl
207
90
207
Pb
Nb
Bi
0.1
1
10
Halflife (ms)
1000
Cooling and bunching:
Cooling and bunching:
Photon-ion coincidence spectroscopy
Ion beam
Laser beam
Quartz lenses
Microchannel
plates
Segmented
photomultiplier
Isomer results
g 9/2
p
1/2
Hafnium charge radii
0.2
β2 = 0.3
Isomer measurement;
Boos et al.
Dubna, Orsay, Mainz
McGill
PRL 72 (1994) 2689
-0.2
2
2
<r > (fm )
0.0
-0.4
β 2 = 0.2
-0.6
-0.8
166 168 170 172 174 176 178 180 182 184 186
Atomic Mass Number
The isomer has a static
quadrupole moment that
is greater than the static
+ dynamic quadrupole
moment of the gs
Sensitivity to diffuseness??
<r 2 > = <r 2 >SCO + 0.72 t
R
2
ρ(0)
ρ (r) =
1+e
4.39(r-R)
t
t
-r2
e 2σ 2
Folded Gaussian
<r 2 > = <r 2 >SCO + 3 σg2
Decrease pairing - σ decreases??
r 2 ρ(r)
r 2 ρ(r)
Droplet model
(2.6%)
(12%)
for a shape expansion in terms
of Legendre polynomials
Neutron number
High-K isomer measurements
Two reported (deformed) results
were those on 178m2 Hf and 177m Lu
Both show reductions in <r 2 > despite
increases in β2
JYFL measurements
130m
Ba
Z=56
N=74
176m
Yb
Z=70
N=106
178m1
Hf
Z=72
N=106
97m1,m2
Y
Oblate
Barium mean square charge radii
(in collaboration with A Bruce)
0.5
β2= 0.3
isomer
2
130m Ba
δ<
δ<r > ((fm )
0.3
0.1
2
(9.5ms)
β2= 0.2
-0.1
β2= 0.1
β2= 0
-0.3
126
130
134
Mass number, A
138
142
All results:
All the spin-aligned isomers measured
show decreases in mean square
charge radii despite increases in Qo
Why?
2
<β >
2
<β> reduction?
IS, B(E2)
178g,m1,m2
Qs
ε
Hf
α
(or β )
Loss of pairing?
r 2 ρ(r)
r 2 ρ(r)
Can you tell them apart??
2
<β >
2
<β>
IS, B(E2)
178g,m1,m2
reduction?
Qs
ε
Hf
α
(or β )
Loss of pairing?
r 2 ρ(r)
r 2 ρ(r)
Yes – spherical spin-aligned isomers
Next – Bismuth
November 20th – 24th
JYFL
209Bi(p,pxn)
204Bi
(10-, 13 ms)
204Bi (17+, 1.07 ms)
204Bi (gs, 12hrs)
203Bi (1/2, 300 ms)
203Bi (gs, 2hrs)
CW + Ti:Sa intra-guide
209Bi
~ 380 nm
(Ti:Sa)
306.7 nm
(CW)
spectra (50mbar)
November 20th – 24th
209Bi(p,pxn)
We can have
substantial partial
pressures of 209Bi in
the gas..
…and a collinear RIS
back-up
For LaSpec…
Direct measurements on high-K isomers…
Calibration of non-optical results;
B-fields in LMS etc
LMS, PAD
-9
-6
-3
AB, NMR
0
3
JYFL optical
6
log(t1/2 )
(Yttrium)
..and neutron deficient
300
2
χ r=1.273
90
200
Y
*
*
*
100
0
200
Fission fragments
150
2
χ r=1.069
89
Y
*
*
100
*
50
10000
800
2
χ r=0.803
88
Y
600
*
*
400
200
*
200
0
150
87
Y
*
*
2
*
χ r=1.082
100
50
10000
86
800
Y
2
χ r=0.944
600
400
-2000
-1000
0
1000
-1500
-500
500
89
Frequency relative to Y ground state resonance (MHz)
“Complete” spectroscopy:
Trap time of flight
measurement of
ground and isomer
state masses
+
Laser measurement
of hyperfine
structures of ground
and isomeric states
Frequency (MHz)
Trap time of flight
measurement of
ground and isomer
state masses
+
Laser measurement
of hyperfine
structures of ground
and isomeric states
0+y 0.36 s
J’s one ‘low’,
one ‘high’
0+x 0.30 s
102 Y
Mass measurement
+
Laser measurement
+
Trap assisted spectroscopy
0+y 0.36 s
J’s one ‘low’,
one ‘high’
0+x 0.30 s
102 Y
Vital if identification of the
ground state is the goal
Pumping in the cooler:
363.3nm pumping
(40% transfer)
1pA of 89Y
continuous beam
University of Manchester
J Billowes, P Campbell, B Cheal, B A Marsh
and B W Tordoff
University of Birmingham
G Tungate, D H Forest,
M D Gardner and M Bissell
University of Jyvaskyla
J Aysto, A Jokinen, ID Moore, H Penttila,
T Eronen, S Rinta-Antila and T Kessler
(KT Flanagan, J Huikari, R Moore, A Nieminen)
‘Slow’ fast beams
Charge exchange
alternatives?