James CubissUniversity of York

jgc511@york.ac.ukOn behalf of the IS534, Sep 2014 collaboration

Hyperfine structure studies of At isotopes using in-source laser spectroscopy at ISOLDE

Z=82

N=126

University of York, United Kingdom

A. N. Andreyev, J. G. Cubiss, B. Whitmore, G. L. Wilson

RILIS, CRIS and ISOLDE, Geneva, Switzerland

S. Rothe, B. A. Marsh, A. M. Sjodin, V. N. Fedosseev, M. D. Seliverstov, N. Imai,

K. Lynch

Institut für Physik, Johannes Gutenberg-Universität Mainz, Mainz, Germany S. Raeder, K. D. A. Wendt

Instituut voor Kern- en Stralingsfysica, K.U. Leuven, Leuven, Belgium

L. Ghys, C. Van Beveren, E. Rapisarda, D. Pauwels, D. Radulov,

Yu. Kudryavtsev, M. Huyse, P. Van Duppen

Comenius University, Bratislava, Slovakia

S. Antalic, Z. Kalaninova, B. Andel

PNPI, Gatchina, Russian Federation A. Barzakh, D. V. Fedorov, P. Molkanov

University of Manchester, UKI. Straschnov, T. E. Cocolios

MR-TOF@ISOLTRAP team:

S. Kreim, V. Manea, +...

University of Liverpool

F. Wearing, A. Gredley

Collaborators

IS534, Sep 2014 collaboration

Previous work on charge radii near Z =82

Pb ISOLDE, PRL98, 112502 (2007) H. De Witte et al.

Po ISOLDE,PRL106, 052503 (2011)T. Cocolios et al.,

2011: Tl isotopes: IS511 ISOLDE and IRIS(Gatchina)

At?

IDS

NICOLEMINIBALL

TAS VITO

MR-ToF

WindmillCOLLAPSCRIS

WITCH

collections

HRS Target

GPSISCOOL

ISOLDE hall & RILIS

1.4 GeV ProtonsFrom PSB

RILIS

205At

Total photon energy cm-1

Ion

co

un

t in

ten

sity

a.

u.

Development of At beams & ionisation scheme

532

nm

224

nm

216

nm

312

- 33

5 nm

609-

645

nm

a) b) c)

795

nm

532

nm

44550 cm-1

0 cm-1

46234 cm-1

57157 cm-1

57269 cm-1

57277 cm-1

58805 cm-1

75151 cm-1

710-

915

nmd)

B. A. Marsh et al., 20013 EMIS conference, NIM B317, p.550 (2013)WM: A.N. Andreyev et al, Phys. Rev. Lett 105, 252502 (2010)MR-ToF MS: R. N. Wolf et al, NIM, A686, 82 (2012)

Our tools for measuring hyperfine splitting (HFS)

HFS spectrum, 205At from Faraday cup

• Fitted using a Voigt profile:- Lorentzian (Laser line shape)- Gaussian (Doppler)

• “Centre of Gravity ” (CoG) is taken from the HFS fits.

• Can extract: - magnetic moment- quadrupole moments- nuclear spins- Δδ<r2>

T½ = 26.9 m

Annular Si Si

Pure 60 keV beam from RILIS+ISOLDE

C-foils20 mg/cm2 Si detectors

60 keV beam from ISOLDE

SiAnnular Si

ff

ff

a

C-foil

LEGe detector

A.N. Andreyev et al., PRL 105, 252502 (2010)

Setup: Si detectors both sides of the C-foil• Simple setup & DAQ: 4 PIPS (1 of them – annular)• Large geometrical efficiency (up to 80%)• 2 fold fission fragment coincidences• ff-gamma coincidences• Digital electronics

Windmill system at ISOLDE

200At

• 3 distinguishable peaks from 3 isomers of 200At.

• Gate on alpha energies to see HFS.

3 isomers of 200At, Windmill

• No shift in CoG, three isomers have same deformation!

• Rmax = the maximum peak rate.

Nα

Wavenumber [cm-1]

200At 6411 keV, 7+T½ = 47 s

6464 keV, 3+T½ = 43 s

6536 keV, 10-T½ = 3.5 s

Nα

Energy [keV]

200Po

Rmax ≈ 20 α/sRmax ≈ 50 α/sRmax ≈ 80 α/s

Isomeric shifts and shape coexistence, 197At

• δ<r2> between isomers.

• Investigating shape coexistence!

T½ = 0.388 sRmax ≈ 100 α/s

T½ = 2 sRmax ≈ 36α/s

Alpha- & beta- decay studies with Windmill, 218At

• Dedicated decay studies.

• Can measure:- Alpha- and gamma- decay energies- Branching ratios- Half-lives

• Secondary confirmation of spin assignments (prompt gammas following β).

• Develop decay schemes.

• Free! By-product of HFS studies!

218AtT½ = 1.5 s

218Fr 214AtT½ ≈ 1 ms T½ = 558 ns

MR-ToF MS: R. N. Wolf et al, NIM, A686, 82 (2012)

• The windmill setup depends on decay measurements.

• No good for long-lived or stable isotopes.

• Better off counting ions with MR-ToF (Multi Reflection Time of Flight spectrometer)! (Frank Wienholtz, 15.12.2014)

MR-ToF at ISOLDE

• Can also deal with isobaric contamination.

MR-ToF – dealing with isobars

T½ = 1.81 h

• Produce HFS by gating on ToF.

Reproducibility with MR-ToF, 203At

MR-ToF, on-line analysis, IS534 (2014)

T½ = 7.4 mRmax ≈ 60 ions/s

Isotopic shift between At isotopes

• Sample of results.

• Difference between CoG gives the isotopic shift.

• From isotopic shift, δ<r2> can be calculated.

• Measuring deformation across the nuclear chart.

• Results from 2 months ago.

• Final analysis underway.

T½ = 32.3 msRmax ≈ 175 α/s

T½ = 7.214 hRmax ≈ 20 ions/s

T½ = 26.9 ms

T½ = 7.03 sRmax ≈ 100 α/s

T½ = 328 msRmax ≈ 5 α/s

Preliminary

Charge radii plot for At – IS534, Sep 2014 N = 126

Spherical regionOnset of deformation

Possible octupole

deformation?

Thank you for listening!

Joyeux anniversaire, ISOLDE!