1. In-source laser spectroscopy of isotopes far from stability (ISOLDE, CERN & IRIS, PNPI)
Anatoly Barzakh
PNPI

2. ISOLDE
IS 511: Shape coexistence in the lightest Tl isotopes studied by laser spectroscopy
IS 534: Beta-delayed fission, laser spectroscopy and shape-coexistence studies
with radioactive 85At beams
IS 534 (addendum): Laser spectroscopy and shape-coexistence studies
with radioactive 79Au beams
Shape Coexistence in the Lead Region studied by laser resonance spectroscopy
A collaboration of ~30 atomic and nuclear physicists
12 institutions
Preliminary results for At and Au isotopes!

3. Magnetic moments, hyperfine structure anomaly and mean squared charge radii of neutron deficient Tl isotopes
IRIS

4. Laser Ion Source at ISOLDE
Laser beams
Experiments
Mass separation
Target Hot Cavity Extractor
Ion Source
Reaction products
(neutral)
Ions
Protons
Target material
60 kV
Isotope/isomer shift
1 ppm
A-1,Z
A,Z
Isotope shift (IS), hyperfine structure (HFS) measurements: The wavelength of the narrow-band laser is scanned across the chosen transition. The photoion current at the collector of the mass separator increases at the resonance.
Detection of photoion current by measuring FC current, a//g or ToF spectra while scanning the frequency

5. Laser Ion Source at IRIS
Laser beams
ion source
Mass separator
protons
target
A substantial increase of the ionization efficiency can be achieved by decreasing of the inner diameter of the laser ion source tube with a corresponding focusing of the laser beam inside. At IRIS facility the laser spot as low as 1 mm in diameter can be provided due to a lens, placed in a distance of 2 m from the ion source

6. Detection: Windmill System at ISOLDE
A. Andreyev et al., PRL 105, (2010)
Annular Si Si
MINIBALL Ge cluster
Annular Si
pure 50 keV beam
from RILIS+ISOLDE Si ff a
50 keV beam
from ISOLDE ff
C-foil
C-foils
20 mg/cm2
Si detectors
The WM technique requires waiting for the decay of the isotope (usually, α-decay). Not practical for long-lived or stable isotopes (or for β-decaying).
Setup: Si detectors from both sides of the C-foil
Large geometrical efficiency (up to 80%)
2 fold fission fragment coincidences
ff-γ, γ-α, γ-γ, etc coincidences

7. Detection: MR-ToF MS at ISOLDE
Multi-reflection time-of-flight mass separator (MR-ToF MS)
~1000 revolutions, ~35 ms, m/Δm ~ 105
MR-ToF MS is not limited by decay scheme or long half-lives
MR-ToF MS offers a way to separate background for direct single-ion detection using MCP (time scale: tens of ms).
R. N. Wolf et al., Nucl. Instr. and Meth. A 686, (2012), S. Kreim et al., INTC-P-299, IS 518 (2011)

8. Tape driving device

9. Amplitudes of the components:
Number of components and their relative intensities give the possibility to determine nuclear spin I
F’2=I+1/2
Jf=1/2
F’1=I-1/2
Positions of the components:
F2=I+1/2
Ji=1/2
F1=I-1/2

10. IS

11. RILIS upgrade CVL to Nd:Yag Green Beams 90 W @ 532 nm UV beam
10kHz rep rate
6 - 8 ns pulses

12. RILIS upgrade Laser ion source at ISOLDE Nd:YAG lasers Dye lasers
Dye+Ti:Sa system
3 Ti:Sa lasers:
5 GHz linewidth
Up to 5 W output power
680 – 1030 nm (fund.)
35 ns pulse length
Laser ion source at ISOLDE
Nd:YAG lasers
Dye lasers
Ti:Sa lasers
Since the two systems can be used either independently or in combination, there exists far greater flexibility for switching from one ionization scheme to another or rapidly changing the scanning step.

13. Isotope shift δ A,A’:
IS/hfs’s were previously measured for 535 nm transition with reliably established F and M for Tl:
J. A. Bounds et al., Phys. Rev. C36, 2560 (1987);
R. Menges et al., Z. Phys. A341 (1992) 475;
H. A. Schuessler et al., Hfi 74 (1992) 13

14. Electronic factor and mass shift for 277 nm transition (IRIS)
Isotope shift δ A,A’:
Δσ for different transitions should lie on the straight line with a slope Fλ1/ Fλ2
F535nm, M535nm F277nm, M277nm
King plot

15. 183Tl, I=1/2, T1/2=6.9 s
184Tl, I=2, T1/2=11 s
185Tl, I=1/2, T1/2=19.5 s
185Tl, I=9/2, T1/2=1.8 s
183Tl, I=9/2, T1/2= 53 ms
184Tl, I=10, T1/2= 37 ms
180Tl, I=(4,5), T1/2=1.1 s
181Tl, I=1/2, T1/2=3.4 s
182Tl, I=(4,5), T1/2=3.1 s
179Tl, I=1/2, T1/2= 0.23 s
183Tl, I=1/2, T1/2=6.9 s
184Tl, I=2, T1/2=11 s
IRIS
186Tl, I=10, T1/2= 2.9 s
IRIS & ISOLDE
ISOLDE
195mTl, I=9/2, T1/2=3.6 s
197mTl, I=9/2, T1/2=0.54 s

16. Isomer selectivity for 184Tl (ISOLDE)
ground state hfs
hfs of the previously unknown isomer (I=10)
with frequency of the narrow-band laser fixed at the marked positions isomer selectivity is obtained and one can investigate properties of the pure isomer state
Hyperfine structures observed for 184Tl with different detection modes

17. Shape coexistence and charge radii in Pb region
Po ISOLDE, T. Cocolios et al., PRL106, (2011)
85At?
Pb ISOLDE, PRL98, (2007) H. De Witte et al.
2011: Tl isotopes: IS511 ISOLDE
and IRIS (Gatchina) ?

18. Development and use of laser-ionized
At beams at ISOLDE
Determination of optical lines and efficient photoionization scheme. First measurement of the ionization potential of the element At
Beta delayed fission of 194,196At
Charge radii and electromagnetic moments measurement for At isotopes

19. Photoionization scheme for the radioactive element At
216 nm
795 nm
532 nm IP
Optimal photoionization scheme.
Narrow band lasers for 1st and 2nd transitions
6p48p(?), J=3/2 or 5/2
6p47s, J=3/2
6p5, J=3/2
In collaboration with TRIUMF-ISAC radioactive ion beam facility with the TRILIS laser ion source

20. Precise determination of the Ionization Potential for the radioactive element At
IP (At)= (84) eV

21. IS534: Isomer selectivity for 197,198At
Isomer selectivity enable ISOLTRAP team to measure masses of 197g,198gAt.
Nuclear spectroscopic information for pure g.s. was obtained

22. IS534: Astatine HFS spectra
216 nm
795 nm
532 nm IP
1st step scanning is better for Δ<r2> extraction
2nd step scanning is better for hfs resolution
(Q and μ determination). But to decipher these hfs’s one should know J for cm-1 level (5/2 or 3/2)

23. IS534: Additional atomic spectroscopic information for Astatine
216 nm
795 nm
532 nm IP
58805 cm-1,
J=3/2 or 5/2
J=3/2
J=3/2
I=1/2
Jf=3/2
F1=1
F2=2
F’1=1
F’2=2
Ji=3/2
795 nm
F1=1
Jf=5/2
F2=2
F’1=2
F’2=3
Ji=3/2
The number of peaks (4 rather than 3) unambiguously
points to J=3/2 for cm-1 atomic state in At

24. King plot for 216 nm and 795 nm lines in At
207
198g
198m
217
F216/F795(At)=-2.26(8)
compare with F256/F843(Po)=-2.241(7)
for similar transitions in Po
Isotope shift δ A,A’:
Δσ for different transitions should lie on a straight line with a slope Fλ1/ Fλ2

25. IS534 October 2012: Charge radii of At isotopesWM FC WM
MR-ToF
Astatine seems to follow Polonium δ<r2> trend — i.e. there is the same early onset of deformation after N=113. Data for lighter isotopes are necessary to verify this conclusion

26. October 2012: IS534 experiment at ISOLDE – Au isotopes
Are the light Au isotopes deformed?
What are the spins of ground and isomeric states?

27. Au hfs spectra Au ionization scheme autoionizing state 674.1 nmIP
autoionizing state

28. Is it possible to discriminate between I=1/2 and I=3/2 for Au isotopes by hfs spectra?
Jf=1/2
F’2
F’1
F’1=0
I=1/2
0—>0 transition is forbidden! F2
F2=1
Ji=1/2 F1
F1=0
Only 3 rather than usual 4 peaks will be seen in the hfs spectra of isotopes with I=1/2 (for I=3/2 — 4 peaks)

29. IS534: Hyperfine Structure Scans for 177,179Au
179Au (WM)
177Au (WM)
179Au 3/2+ calculated
179Au 1/2+ calculated
Number of peaks and their intensities ratio
fix ground state spins of 177,179Au: I=1/2

30. Why is 1/2+1/2+ 181Tl177Au a decay hindered?
m~1.6mN , pure sph. 3s1/2,
(as in the heavier Tl’s)
1/2+
HF>3
I=3/2
m~1.1mN , (preliminary)
mixed/def/triaxial 3s1/2,/d3/2
1/2+
Plot from A.Andreyev et al., PRC 80, (2009)

31. Summary: Charge Radii in Pb region
At seems to follow Po unusual δ<r2> trend
“Back to sphericity” in the lightest Au isotopes
Magnetic/quadrupole moments will be deduced
Large amount of by-product nuclear spectroscopic information on At and Au and their daughter products

32. Conclusions
IS’s and hfs’s for 10 At isotopes (isomers) were measured for two transitions, 216 nm and 795 nm, The fast switching between these modes of scanning provides much more flexibility to experiment and gives more reliable and complementary data for analysis (especially for atoms without known spectroscopic information).
MR-ToF mass separator was used for photo-ions detection for the first time. This method seems to be indispensable for measurements with great surface ionized background and for long lived isotopes with great yield and/or absence of alpha decay mode.
Using WM installation for photo-ions detection gives the possibility to obtain wealth of additional nuclear spectroscopic information (decay schemes, spin and parity assignment etc.) without supplementary time requirement.
Coordinated (ISOLDE&IRIS) program for Tl isotopes investigation enabled us to use both installation more efficiently.
Very interesting results for At and Au isotopes by IS/hfs measurements were obtained: “inverse jump of deformation”, unexpected spin assignments, shape isomers etc. The study of shape coexistence in the lead region will be continued: to go further for Au’s, to fill the gaps and go further for At’s (ISOLDE), to investigate Bi isotopes (IRIS), etc.

34. Hyperfine structure anomaly for Au isotopes

35. Additional nuclear spectroscopic information from Tl isotopes decay
IRIS: 30 new 189Hg γ-lines from 189mTl decay
are unambiguously identified by hfs pattern and their relative intensities are determined
ISOLDE: decay schemes for some Tl isotopes
are determined

36. 183Tl, I=1/2, T1/2=6.9 s
184Tl, I=2, T1/2=11 s
185Tl, I=1/2, T1/2=19.5 s
185Tl, I=9/2, T1/2=1.8 s
186Tl, I=10, T1/2=2.9 s
195Tl, I=9/2, T1/2=3.6 s
197Tl, I=9/2, T1/2=0.54 s
186Tl, I=7, T1/2=27.5 s
187Tl, I=9/2, T1/2=15.6 s
188Tl, I=7, T1/2=71 s
190Tl, I=7, T1/2=3.7 m
189Tl, I=9/2, T1/2=84 s
190Tl, I=2, T1/2=2.6 m
191Tl, I=9/2, T1/2=5.2 m
192Tl, I=7, T1/2=10.8 m
192Tl, I=2, T1/2=9.6 m
194Tl, I=7, T1/2=32.8 m
193Tl, I=9/2, T1/2=2.1 m
194Tl, I=2, T1/2=33 m
203Tl, I=1/2, stable
207Tl, I=1/2, T1/2=4.77 m
previously measured for
transition (535.2 nm)
repeated for another atomic transition
(276.9 nm)
for King-plot calibration …