High-spin states in octupole -deformed 219 Ra

Institute of Physics NPPD Conference 2011

High-spin states in octupole-deformed 219Ra

By Chris Wilson

Institute of Physics NPPD Conference 2011

Octupole deformation

I. Ahmad and P. Butler, Ann. Rev. Nucl. Part. Sci. 43 (1993)

Institute of Physics NPPD Conference 2011

The light actinides

3 j

W. Nazarewicz and P. Butler, Rev. Mod. Phys. 68 (1996)

Institute of Physics NPPD Conference 2011

Rotational consequences

)2()2(

)1()1(2

)(

)(

IEIE

IEIE

I

I

)1()1(2

1)()( IEIEIEIE

Parity splitting

Ratio of rotational frequencies

W. Nazarewicz and P. Olanders, Nucl. Phys. A441 (1985) 420-444

Institute of Physics NPPD Conference 2011

S. Frauendorf, Phys. Rev. C77, 021304(R)(2008)

Condensation of octupole phonons

Institute of Physics NPPD Conference 2011

Light-actinide nuclei

18O (95 MeV) + 208Pb → 226Th*226Th* → 222Th* + 4n → 220Ra* + α2n → 219Ra* + α3n

95 %

Experimental method

Institute of Physics NPPD Conference 2011

Gamma-ray detection

Continuum gamma rays from fast-fission

Discrete gamma rays from evaporation residues

Neutron peaks

Gammasphere: 110 large-volume high-purity germanium detectors for use in gamma-ray spectroscopy experiments.Based at Argonne National Laboratory in Chicago

Institute of Physics NPPD Conference 2011

HERCULES

HERCULESHigh-Efficiency Residue Counter Under Lots of Elastic Scattering 64 plastic scintillator detectors for evaporation-residue detectionW. Reviol et al. Nucl. Inst. Meth. A451 (2005)

Gammasphere(ball opened)

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Background reduction

Evaporation residues Time of flight

Pulse height

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Gamma-coincidence spectra

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New high-spin states in 219RaP. D. Cottle et al., Phys. Rev. C36 (1987) 2286M. Wieland et al., Phys. Rev. C45 (1992) 1035L. A. Riley et al., Phys. Rev. C62 (2000) 021301

Institute of Physics NPPD Conference 2011

Rotational consequences

Institute of Physics NPPD Conference 2011

Rotational consequences

Institute of Physics NPPD Conference 2011

Rotational consequences

Institute of Physics NPPD Conference 2011

Rotational consequences

Institute of Physics NPPD Conference 2011

Summary

• New high-spin states do not provide evidence for the condensation of rotationally-aligned octupole phonons.

• 219Ra has either: 1. A spherical core unstable to both quadrupole and octupole vibrations,

with the octupole vibration enhanced by the odd g9/2 neutron2. A static octupole deformation strongly coupled to the odd g9/2 neutron

• Greater detection sensitivity is required to probe the highest spin states

Institute of Physics NPPD Conference 2011

C.L.Wilson, J.F.Smith, R.Orlandi, S.D.Pain, K.M.Spohr, and D.A.TorresSchool of Engineering, University of the West of Scotland,

Paisley, PA1 2BE, UK

W.Reviol, D.G.Sarantites, X.Chen, and J.SnyderDepartment of Chemistry, Washington University, St. Louis, MO 63130

M.P.Carpenter, C.J.Chiara, R.V.F Janssens, B.P.Kay, F.G.Kondev, C.J.Lister, D.Seweryniak, and S.ZhuArgonne National Laboratory, Argonne, Il 60439

A.N.WilsonDepartment of Physics, Australian National University,

Canberra ACT 0200, Australia

Thanks to UWS and my collaborators

Institute of Physics NPPD Conference 2011

Enhanced E1 transitions

Institute of Physics NPPD Conference 2011

States labelled by spin and parity (Jp)

g

g

g

g

g

g

Ground state

Rotational excited states