Transcript 2 + - CERN Indico

Nuclear moments, spins and charge radii of copper
isotopes from N=28 to N=50 by collinear fast-beam
laser spectroscopy
CERN-INTC-2005-031/-P-200
Spokesperson: Kieran Flanagan
K.U. Leuven: K. Flanagan, M. De Rydt, P. Himpe, P. Lievens G.
Neyens, D. Yordanov and N. Vermeulen.
Universität Mainz: K. Blaum, M. Kowalska, R. Neugart
The University of Manchester: J. Billowes, P. Campbell
GANIL: J.C. Thomas
The University of Birmingham: G. Tungate.
Recent highlights from COLLAPS
• Magnesium
- Ground-state spin and g factor
of 31Mg Phys. Rev. Lett. 94:022501
2005
- Magnetic moments of 27,29Mg
- Quadrupole moment of 29Mg
- Isotope shift measurements 2427Mg
- Hyperfine splitting of 33Mg
PhD theses: M. Kowalska,
D.Yordanov
• Lithium
-Revaluation of the magnetic and
quadrupole moments of 8,9Li
Phys. Rev. C 72, 044309 (2005)
-Quadrupole moment of 11Li
In preparation
Status of laser measurements of
moments and radii
Future area of interest including
this work presently proposed
• Production
at ISOL facilities
• Suitable transitions for tunable
lasers exist only for the atom
• Losses in the neutralization
process and through optical
pumping into dark states
Kluge & Nörtershäuser 2003
Experimental technique
• Collinear laser spectroscopy with the
COLLAPS setup
28
Physical motivation
50
Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn
30
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu Cu
29
55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79
Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni Ni
28
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78
• Magnetic moments, high sensitivity to the
migration of the 5/2- level with neutron excess
• Spin assignment of ground and isomeric states
• Quadrupole moments
• Changes in the mean square charge radii.
• Evolution of nuclear structure towards N=50
and the onset of deformation
Systematic migration of nuclear
states in copper isotopes
•5/2- level associated with the π(f5/2) orbital
E(keV)
1/25/2-
1000
57 59 61 63 65 67 69 71 73
Mass number
S. Franchoo et al. Phys. Rev. C 64 054308
A.F. Lisetskiy et al. Eur. Phys. J. A, 25:95, 2005
N.A. Smirnova et al. Phys. Rev. C, 69:044306, 2004
I=5/2- level:
•Remains static between
57-69Cu at ~1MeV
•Systematically drops in
energy as the ν(g9/2)
shell begins to fill
•Predictions on the
inversion of the ground
state lie between 73Cu
and 79Cu.
•Experimental evidence
for the inversion to occur
at 75Cu.
Shell model with realistic interaction (G-matrix)
and different monopole modifications
4
Magnetic moment (n.m.)
• High sensitivity to the
monopole shift in
measured magnetic
moments.
• Magnetic moment
calculations assuming
a 5/2- ground state in
75Cu and beyond show
reasonable agreement
with experimental data.
• Higher resolution data
required.
3,5
3
2,5
2
1,5
1
0,5
0
55 57 59 61 63 65 67 A69 71 73 75 77 79 81
N=28
N=50
A. Lisetskiy (OXBASH)
no quenching
0.7gs
N. Smirnova (ANTOINE), monopole by Nowacki
Ground and excited state spin assignment
π ν-coupling
Jπ
E/keV
(6-) 721.6
T1/2/S
225
β =16%
5-
4E/keV
68Cu
0
31.1
β =100%
Jπ
6-
3-
1+
πf5/2νg9/2 7
2-
E/keV
T1/2/S
242.4(3) 6.6(2)
β ≈95%
IT ≈ 5%
1+
(3-) 101.1(3) 33(2)
β ≈50%
IT = 50%
πp3/2νp1/2-1(g9/2)2+
(6-)
IT = 84%
1+
70Cu
2+
5-
4-
3-
πp3/2νg9/2 6-
69Cu
π
69Ni
ν
0
44.5(2)
β ≈100%
J. Van Roosbroeck
Phys. Rev. Lett. 92:112501 2004
J. Van Roosbroeck
Phys. Rev. C 69:034313 2004
72Cu
A(72Cu) = 5.4(1) GHz
Cu I S1/2 – P1/2
65
A( Cu) = 12.48(7) GHz,
0.04
μ(65Cu) = 2.3817(3) n.m.
Jπ
82 M1
(4-)
137 E1
(3-)
(2+)
270
51 E2
(6-)
376
Normilized intensity
376 E1
(1+)
652 keV
847 keV
0.03
1004 keV
1253 keV
0.02
0.01
219
0
30534.5
30535.1
138
0
30536.2
frequency ( cm-1)
Contrary to results from insource laser spectroscopy!
β-decay and γ-ray
spectroscopy
This proposal
studies
aims to resolve
this inconsistency.
H. Mach, Symposium on Nuclear Structure Physics
University of Göttingen, 2001
M. Stanoiu, PhD thesis, Université de Caen 2003
J.C Thomas, et al. Submitted to Phys. Rev. C
30535.6
I
μ(μnm
)
Exp.
μ(μnm)
Cal.
1
±0.92
±2.03
2
±1.10
+2.76
3
±1.18
-2.74
4
±1.22
-0.99
5
±1.25
+0.43
6
±1.27
+1.66
Onset of deformation
• Evidence from
ISOLTRAP.
• Upward kink in the
plot of S2N.
• Further confirmation
will be obtained from
the model
independent
measurements of Q
and δ‹r2›.
C. Guénaut et al., to be published
Further evidence for large deformation from
isomeric shift data
• No mass shift in system
• Pure field effect
• Sensitivity to isomer shift in
low resolution in-source
spectroscopy
70Cu
Isomer shift in
68Cu~390(250)MHz
• Enhanced Isomeric shift
observed in 70Cu
• δν70g,70m1 ~ 900(230)MHz
• δν70g,70m2 ~ 1100(220)MHz
L. Weissman et al. Phys. Rev. C, 65:024315, 2002
S. Gheysen et al. Phys. Rev. C, 69:064310, 2004
Experimental requirements for fluorescence
spectroscopy on the COLLAPS beam line
• Regular proton pulse
structure.
• Low noise on the
separator voltage
•Suppression of Isobaric
contamination
Current limit for optical
detection continuous ion
beam: 107 ions/μC
Furtherbackground
optimization
of light by
collection
region, at best an order of
• •Photon
detected
PMT ~1000-2000/s
improvement.
• magnitude
Efficiency looses
due to metastable state population during
•RFQ cooler: Improved beam emittance.
neutralization
Bunched
beam
spectroscopy,
background suppression by
• Atom-laser overlap
in the
light
collection region
a factor
up transit
to 104 from vapour cell to light collection
•Optical pumping
during
region
Beam time request
• Copper isotopes A = 62-72
28 shifts
(UC2graphite target and RILIS using GPS)
• Copper isotopes A = 59-61
9 shifts
(ZrO2/felt target and RILIS using GPS)
Total
37 shifts
High resolution measurements of magnetic dipole
and electric quadrupole moments, ground and
isomeric state spins identification and mean
square charge radii measurements across the
whole isotope chain
• Stable copper isotopes using RILIS
(during the winter shutdown period 2005-2006)
10 shifts
Essential for studying the neutralization process and
optimizing the light collection region for atomic
spectroscopy.
Collinear spectroscopy of copper
IP 7.7eV
1. Voltage tuning of ion beam
2. Neutralization within Na or Li
vapor
Na Charge exchange
5.1eV
2P
1/2,3/2
327nm
324nm
3. Transit of atomic beam between
Vapor cell and light collection
region.
4. Detection of resonant
fluorescence in the light collection
region
2D
3/2
2D
5/2
2S
1/2
Cu I
Spins, moments and radii of Mg isotopes
GOALS : determine the ground state spins and moments of 27,29,31,33Mg isotopes
determine spin and moment of 21Mg
determine changes in mean square charge radii of 24,25,26,27,28,29,30Mg
 onset of deformation towards N=20 ?
 mixing of intruder states into the ground state wave functions around N=20
 borderlines of the island of inversion
Isotope shifts measured via optical detection of HFS
Si
29
Si
29
Si
28
Si
29
Si
30
Al
26
Al
27
Al
28
To be done: 28,29,30Mg (improve background for optical detection)
To investigate 31Mg via b-asymmetry detection of HFS
Si
Si
Si
Si 23
SiMg Si
Si and b-asym detection of HFS
 test:
optical
31
32
33
34
35
36
37
Al
29
Al
30
Al
31
Al
32
Al
33
Al
34
Al
35
Al
36
Mg
21
Mg
22
Mg
23
Mg
24
Mg
25
Mg
26
Mg
27
Mg
28
Mg
29
Mg
30
Mg
31
Mg
32
Mg
33
Mg
34
Mg
35
Na
20
Na
21
Na
22
Na
23
Na
24
Na
25
Na
26
Na
27
Na
28
Na
29
Na
30
Na
31
Na
32
Na
33
Na
34
21Na
16
18
Reducuction of
contamination required
I and m measured:
20
Meassured HFS β-asymmetry (2%)
Sept. 2005
D. Yordanov, analysis in progress
1 run needed to measure I and g
G.Neyens et al., Phys. Rev. Lett. 94 (2005) 022501
M. Kowalska et al., Eur. Phys. J. A25 (2005) 193
D. Yordanov et al., Special Issue Balkan Phys. Lett. (2005)
M. Kowalska et al., paper + PhD thesis in preparation
Collaboration
• K.U. Leuven: 2 members of staff, 1 postdoc, 4 PhD students
• University of Mainz: 2 members of staff, 2 PhD students
• University of Manchester: 2 members of staff, 1 postdoc, 3 PhD
students
• University of Birmingham: 1 member of staff 1 postdoc, 2 PhD
students.
•GANIL: 1 member of staff
Total: 8 member of academic staff , 3 postdocs, 11 PhD
students .
At CERN
1 postdoc, 2 PhD students
Effect of improved ion beam for fluorescence
spectroscopy on the COLLAPS beam line
Current limiting factors for laser spectroscopy
• Background of scattered laser light detected by PMT ~2000/s.
• Detection efficiency within the light collection region.
• Broadening of lineshape due to voltage ripples.
Within the light collection
region the ion beam should
have zero divergence (parallel
beam)
Currently the minimum
ion beam diameter
reached is ~6mm
In order to maximize the
detection efficiency good
overlap between laser and
ion beams is necessary
This results in a high background level from
scattered light
Effect of improved ion beam for fluorescence
spectroscopy on the COLLAPS beam line
•A
reduction in the ion beam diameter will allow the laser to be
reduced in diameter (and therefore power) with no detrimental
effect on the detection efficiency.
• Immediate consequences for the detected background
Bunching ions in the RFQ cooler
Trap and accumulates ions – typically
for 300 ms
Releases ions in a 15 µs
bunch
Background suppression equal to the
ratio of the trapping time to the
bunch width 300ms/15 µs ~ 104
1. Nuclear properties from laser spectroscopy
ppm shift
Isotope shift of
atomic transition
176Hf
178Hf
Hyperfine structure
of atomic transition
Analysis yields the
change in nuclear
mean square charge
radius
Nuclear size, static and
dynamic deformations
Nuclear spin I
(Isotope shift found
using centroids of
hyperfine multiplet)
Magnetic moment µ
Quadrupole moment Qs
177Hf
200
8000 ions/sec
BEFORE
5.3 hours
100
(Photon-ion
coincidence
method)
Laser frequency
For optical
measurements
the minimum
ion beam
intensity is 106/s
Photons from laser-excitation of
radioactive 88Zr
30
AFTER
Compare to
COLLAPS
2000 ions/sec
48 minutes
0
Data from work at Jyvaskyla JYFL
J.Billowes