Some Ideas for A Future Plan of Research at ATLAS

Xiaofeng Wang

The Riley Group at FSU

• (Enhanced) stable beam + (Digital) Gammasphere (GS)

• Radioactive beam from CARIBU + (Digital) GS

If necessary, combined with FMA, charged-particle detector array (e.g., CHICO, Microball…).In the future, GRETINA will also be considered.

Favored Experimental Conditions at ATLAS

Extend Ultrahigh-spin story to Ho, Dy, Hf… nuclei(search for new collective structures at ultrahigh spin)

Paul et al., PRL 98, 012501 (2007).

65hbar!

157,158Er(observed/measured)

154(observed/proposed)

159,160(observed)

Ho

Dy

162Hf(proposed)

+ Lifetime measurement (quadrupole moment) to determine the deformation

Search for 2-phonon (and even multiple-phonon) octupolebands in Actinides, Lanthanides

•“Unsafe” Coulomb excitation (multiple-neutron transfer): need radioactive target.

•Fu-Ev reaction: need radioactive beam (CARIBU?).

Wang et al., PRL 102, 122501 (2009).

0-pn 1-pn 2-pn

240Pu

Nazarewicz et al., NPA 429, 269 (1984).

Search for Tetrahedral Symmetryin Lanthanides, Actinides

•Measure branching ratios.

•Measure dipole transition probabilitiesof interband lines.

Round-edge pyramid shape

Dudek et al., PRL 88, 252502 (2002).

Predicted Tetrahedral magic numbers:Zt = 16, 20, 32, 40, 56-58, 70, 90-94.Nt = 16, 20, 32, 40, 56-58, 70, 90-94.

242 94Pu

Low-spin:Tetrahedral?

High-spin:Octupolevibration?

() (+)

Wang, Ph.D. thesis, Notre Dame (2007).

Identify decay path of SD, TSD structures in Er, Yb, Hf… nuclei

Lauritsen et al., PRL 88, 042501 (2002).

“Floating” candidate bands observed previously.

154Er: 1 TSD, 1 SDLagergren et al., PRL 87, 022502 (2001).

157Er: 2 TSDs; 158Er: 2 TSDsPaul et al., PRL 98, 012501 (2007).

159Er: 1 TSD; 160Er: 2 TSDsOllier et al., submitted to PRC.

160Yb: 1 TSD.Aguilar et al., PRC 77, R021302 (2008).

174Hf: 8 TSDs/SDsDjongolov et al., PLB 560, 24 (2003).Hartley et al., PLB 608, 31 (2005).

Search for Low-lying SD, TSD (wobbling?) in n-rich 44Ru

•PES calculations show low-lying (I ~ 20hbar) SD/TSD minima and fruitful coexisting shapes in n-rich Ru, best cases: 110,112Ru...

•We intend to study 108-112Ru. Need to populate up to I ~ 30hbar.

•Reactions: Safe or unsafe Coulex – n-rich Ru beam (107-112Ru yield>106 from CARIBU) on thick target (e.g., 208Pb), or on thin target with charged-particle detectors (e.g., CHICO) used.

•Trigger set on target nuclei.

Skalski et al., NPA 617, 282 (1997).

Collaboration

FSU: X. Wang, M. A. Riley, S. Yuan, C. TealUSNA: D. J. HartleyArgonne: M. P. Carpenter, C. J. Chiara, R. V. F. Janssens, F. G. Kondev, T. Lauritsen, S. ZhuLiverpool (UK): E. S. Paul, A. J. Boston, H. C. Boston, D. Judson, P. J. Nolan, J. Revill, C. UnsworthDaresbury (UK): J. Simpson, J. OllierTennessee: L. L. RiedingerNotre Dame: A. D. Ayangeakaa, U. Garg, J. MattaBerkeley: P. Fallon, M. K. PetriLund (Sweden): I. RagnarssonOak Ridge: D. Radford, C.H. YuiThemba (South Africa): J. F. Sharpey-Schafer