Search for Fingerprints of Tetrahedral Symmetry in the Rare …lea-colliga/public-docs/2008MeetingCatania/Monday… · Search for Fingerprints of Tetrahedral Symmetry in the Rare

Search for Fingerprints of Tetrahedral Symmetry Search for Fingerprints of Tetrahedral Symmetry in the in the Rare EarthRare Earth and and ActinideActinide RegionsRegions

D. CurienD. Curien IPHCIPHC--DRSDRSStrasbourgStrasbourg

∆∆ Part of the Tetranuc Project: Part of the Tetranuc Project: open collaboration of more than 20 institutions both European aopen collaboration of more than 20 institutions both European and non nd non EuropeanEuropean

∆∆ Main collaborators for this work:Main collaborators for this work:J.DudekJ.Dudek, K. , K. MazurekMazurek, , F.HaasF.Haas, Q.D. , Q.D. TuyenTuyen, O. Stezowski, L. , O. Stezowski, L. RiedingerRiedinger, , D. Hartley, R. BarkD. Hartley, R. Bark

D. CurienD. Curien LEALEA--Catane 17Catane 17--19 October 200819 October 2008 22

Physics Motivation: Physics Motivation: bottom linesbottom lines

∆∆ Existence of highExistence of high--rank symmetries predicted by rank symmetries predicted by the nuclear meanthe nuclear mean--field theoryfield theory

∆∆ Here we consider two point group symmetries:Here we consider two point group symmetries:

•• Tetrahedral Tetrahedral (pyramid like shape)(pyramid like shape)24 symmetry elements24 symmetry elements

•• Octahedral Octahedral (diamond like shape)(diamond like shape)48 symmetry elements48 symmetry elements

∆∆ In quantum description the Hamiltonian has 48 In quantum description the Hamiltonian has 48 and 96 symmetry elementsand 96 symmetry elements

almost the highest possible numbersalmost the highest possible numbers(Triaxial nuclei = only 4 symmetry elements)(Triaxial nuclei = only 4 symmetry elements)

See J. Dudek talk on TuesdaySee J. Dudek talk on Tuesday


Consequence: Consequence: huge gapshuge gaps

Observe big gaps at Z=56Observe big gaps at Z=56--58, 6858, 68--70 and N=9070 and N=90--94, 11294, 112

In the Rare Earth regionIn the Rare Earth region


Consequence: Consequence: huge gapshuge gaps

Observe big gaps at Z= 64, 70, 90Observe big gaps at Z= 64, 70, 90--94,100 and N=112, 13694,100 and N=112, 136--142142

In the Actinides regionIn the Actinides region


New Magic Numbers:New Magic Numbers:

•• The tetrahedral nuclei are predicted around the The tetrahedral nuclei are predicted around the following new shell closures:following new shell closures:

((ZtZt, , NtNt) = (32, 40, 56, 64, 70, 90, 136)) = (32, 40, 56, 64, 70, 90, 136)

•• Corresponding to the doubly magic nuclei:Corresponding to the doubly magic nuclei:

64643232Ge, Ge, 7272

3232Ge, Ge, 88883232Ge, Ge, 8080

4040Zr, Zr, 96964040Zr, Zr, 110110

4040Zr, Zr, 1121125656Ba, Ba,

1261265656Ba, Ba, 146146

5656Ba, Ba, 1341346464Gd, Gd, 154154

6464GdGd,, 1601607070YbYb, , 226226

9090ThTh


DoublyDoubly--Magic Tetrahedral NucleiMagic Tetrahedral Nuclei


Experimental Signs ?Experimental Signs ?

∆ Tetrahedral nuclei = oriented objectRotational bands

∆ There exist 4 types of octupole shapes:Y31, Y30, Y32, Y33

∆ Tetrahedral symmetry Y32with negative parity

∆ Tetrahedral symmetry implies Qt=0Rotational bands without E2’s!!


Do we have Do we have Candidates Candidates close to the close to the Tetrahedral Magic Numbers?Tetrahedral Magic Numbers?

Z=62 Z=62 Z=64 Z=66


Obvious Experimental Observable:Obvious Experimental Observable:Branching Ratios Branching Ratios B(E2)inB(E2)in//B(E1)outB(E1)out

∆∆ Exact symmetry : Exact symmetry : QQtt= 0 but also= 0 but alsoDDtt=0 =0 only E3 transition, no E1!only E3 transition, no E1!but transition probability E1/E3 ~10but transition probability E1/E3 ~1012 12 ! ! no E3!no E3!

Partial symmetry breaking Partial symmetry breaking (zero(zero--point motion, spin, point motion, spin, …….).)Residual polarisation partly allowing E1 and E2 transitionsResidual polarisation partly allowing E1 and E2 transitions

∆∆ We may expect a spin dependence of the branching ratios asWe may expect a spin dependence of the branching ratios ascompared with classical octupolecompared with classical octupole


Obvious Experimental Observable: Obvious Experimental Observable: B(E2)inB(E2)in//B(E1)outB(E1)out

B(EB(E22))in/in/B(EB(E11))outout * 10 * 10 6 6 fmfm22


Where in the Periodic Table?Where in the Periodic Table?

9696Zr Zr Spiral2Spiral2B(E3)(W.u.)=57B(E3)(W.u.)=57

UraniumUranium

156156GdGd


Search in the Rare Earth Region:Search in the Rare Earth Region:approved proposalsapproved proposals

Site Site Main goalsMain goals ReactionReaction StatusStatus

IPNIPN--Orsay Orsay Oscar Oscar 156156GdGd(D. Curien)(D. Curien)

•• excitation functionexcitation function•• γ γ −− γγ

Fusion EvaporationFusion Evaporation154154Sm(Sm(αα,2n) ,2n)

Run 12/06Run 12/06Analyzed Analyzed J.RobinJ.Robin IPHCIPHC

JYFLJYFL--JyvJyvääskylskylää 156156GdGdJurogamJurogam(J. Robin, D. Curien)(J. Robin, D. Curien)

•• γ γ −− γ γ −− γγ•• branching ratiosbranching ratios•• new bands, new new bands, new interinter--band transitionsband transitions

Fusion EvaporationFusion Evaporation154154Sm(Sm(αα,2n),2n)

Run 10/07Run 10/07Partially analysed at IPNLPartially analysed at IPNLQ.D. Q.D. TuyenTuyen, O. Stezowski, O. Stezowski

ILLILL--Grenoble Grenoble GamsGams 156156GdGd(B. (B. LaussLauss, M. , M. JentshelJentshel, D. , D. Curien, J. Dudek )Curien, J. Dudek )

•• forbidden E2forbidden E2’’ss•• level lifetimeslevel lifetimes Thermal neutronsThermal neutrons

155155Gd(n,Gd(n,γγ) E=TH ) E=TH

Run 12/07 Run 12/07 Analysed at ILL, results Analysed at ILL, results under investigationunder investigationW. UrbanW. Urban

LNLLNL--Legnaro Legnaro GaSpGaSp 156156GdGd(R. Singh, G. de Angelis(R. Singh, G. de AngelisD. Curien, J. Dudek)D. Curien, J. Dudek)

•• quadrupole quadrupole moments moments ••DSAMDSAM

Coulex Coulex 5858NiNi Plan Dec 08Plan Dec 08--Jan 09?Jan 09?

iThemba iThemba AfroditeAfrodite 154154GdGd(R. Bark)(R. Bark)

•• B(E1) matrix B(E1) matrix elementselements Coulex Coulex 8484KrKr Plan for March 09Plan for March 09

ANL ANL GammasphereGammasphere 156156DyDy(L. (L. RiedingerRiedinger))

•• branching ratiosbranching ratios Fusion EvaporationFusion Evaporation148148Nd(Nd(1212C,4n)C,4n)

Scheduled for November Scheduled for November 0808


Why Why 1561566464GdGd92 92 ? ?

Useful production reactions (low spin) in the literature:

155Gd(n,γ) 156Gd(n,n'γ) 154Sm(α,2nγ)150Nd(13C,α3nγ) Coulomb Excitation 158Gd(p,t) 154Gd(t,p)

Negative parity band oddNegative parity band odd--spinsspins: : known as a vibrational octupole band with an evenknown as a vibrational octupole band with an even--spin partnerspin partner

All of them failed to see the E2All of them failed to see the E2’’s below s below Spin 9Spin 9

J. Konijn et al., NPA 352 (1981) 191-220


Branching Ratios Branching Ratios

R=R=B(E2)B(E2)inin / / B(E1)B(E1)outout x10x1066

50 (10)

16 (3)

6 (2)

7 (2)

15 (7)

NPB even member:NPB even member:R~270 R~270

from Ifrom Iππ=10=10-- to I=4to I=4--


156156Gd JYFL exp.Gd JYFL exp.

•• Goals: Goals: γγ−−γγ−−γγ ((mutipletsmutiplets))–– Forbidden E2Forbidden E2’’ss–– Branching ratiosBranching ratios

•• 154154Sm(Sm(αα,2n) 27 MeV,2n) 27 MeVExcitation function OSCARExcitation function OSCAR--IPNOIPNO

•• First experiment with full TNT First experiment with full TNT digital electronicsdigital electronics

First results: First results: ZakopaneZakopane 2008 2008 Q. D. Q. D. TuyenTuyen (IPNL)(IPNL)


Negative Parity EvenNegative Parity Even--Spin BandSpin Band


Negative Parity OddNegative Parity Odd--Spin BandSpin Band


Direct comparisonDirect comparison


156156Gd partial level scheme from JYFLGd partial level scheme from JYFL


Branching RatiosBranching Ratios

XX 100!100!


Two comments:Two comments:

∆∆ B(E2)/B(E1) branching ratios going towards zero; two B(E2)/B(E1) branching ratios going towards zero; two possible reasons:possible reasons:

–– Q2Q2 0 for 0 for αα3232: no E2 : no E2

–– Large B(E1;ILarge B(E1;I II--1) ?1) ?

At N=90 (At N=90 (152152Sm, Sm, 154154Sm) Sm) enhanced B(E1)enhanced B(E1) values have been reported values have been reported as large as as large as 44--40.1040.10--3 3 W.uW.u.. for 1for 1-- 0+ transition 0+ transition

giving giving Q(npb)~2Q(npb)~2--7 7 xx Q(gsbQ(gsb) (at 12 and 40 ) (at 12 and 40 e.be.b. ). ) is this SD???is this SD???

The first 1The first 1-- state could not be tetrahedral state could not be tetrahedral (which is good!)(which is good!)

But is such a huge value compatible with octupole vibration eithBut is such a huge value compatible with octupole vibration either?er?

Lee Lee RiedingerRiedinger & Rob Bark, invited Professors at IPHC& Rob Bark, invited Professors at IPHC


Second CommentSecond Comment

∆∆ Rob Bark performed band mixing calculations mainly for Rob Bark performed band mixing calculations mainly for 160160YbYb–– Even spin states Even spin states Q~5 Q~5 ebeb incompatible with a tetrahedral bandincompatible with a tetrahedral band–– Odd spin states chiOdd spin states chi--squared values obtained for the fit of branching squared values obtained for the fit of branching

ratios seem not to converge if one takes all bandratios seem not to converge if one takes all band--states for the fitstates for the fitA firm conclusion is not yet possible and would be in any A firm conclusion is not yet possible and would be in any case model dependentcase model dependent

therefore the conclusion at this level of the discussion is therefore the conclusion at this level of the discussion is that we need to have a direct measurement of the that we need to have a direct measurement of the

absolute transition rates in these nuclei for as many as absolute transition rates in these nuclei for as many as possible states in the tetrahedral candidates bandspossible states in the tetrahedral candidates bands


•• white : possible tetrahedral nucleiwhite : possible tetrahedral nuclei•• yellow yellow : octupole nuclei: octupole nuclei•• greengreen : coexistence of the two: coexistence of the two

Actinide RegionActinide Region

New Shape Coexistence?New Shape Coexistence?


Branching RatiosBranching Ratios

statestate 220Th220Th(90,130)(90,130)

222Th222Th(90,132)(90,132)

224Th224Th(90,134)(90,134)

226Th226Th(90,136)(90,136)

228Th228Th(90,138)(90,138)

230Th230Th(90,140)(90,140)

232Th232Th(90,142)(90,142)

2121-- 0.2(?)0.2(?) -- --

1919-- -- 0.3(?)0.3(?) 22 -- --

1717-- -- 0.4(2)0.4(2) ?? 2.32.3 -- -- --

1515-- 1.8 ?1.8 ? 0.4(2)0.4(2) 0.40.4 22 -- ?? ??

1313-- ?? 0.3(2)0.3(2) 0.50.5 ?? 1616 ?? ??

1111-- 0.40.4 0.4(2)0.4(2) 0.40.4 22 1313 ?? ??

99-- 0.30.3 0.4(2)0.4(2) ?? 22 1414 156156(64)(64)

182182(41)(41)

77-- 0.40.4 0.4(3)0.4(3) ?? ?? 00 ?? 22642264(470)(470)

55-- 00 00 00 00 00 ?? 00

33-- 00 00 00 00 00 00 00

B(EB(E22))in/in/B(EB(E11))outout * 10 * 10 66


Uranium Isotopes CaseUranium Isotopes Case

208208Pb(Pb(2222Ne,4n)Ne,4n)P. GreenleesP. Greenlees

231231Pa(p,4n)Pa(p,4n)

231231Pa(p,2n)Pa(p,2n) 232232Th(Th(αα,2n),2n)

230230Th(Th(αα,2n),2n) 236236U(d,pn)U(d,pn) multimulti--CoulexCoulexD. WardD. Ward

No E2’s !B(E2)/B(E1)*106

0.4

0.4

0.4

1.3

Hindranced E1’s 3*10-8

P. P. ZeyenZeyen et al. et al. Z.Phys.AZ.Phys.A 2328,399 (1987):2328,399 (1987): ee--γγ coincidencecoincidence

Octupole def. Octupole def. Octupole Octupole vibvib. . or or Tetrahedral shapeTetrahedral shape


Another last Comment:Another last Comment:

Question:Question: are the E2 not seen are the E2 not seen because of enhanced E1because of enhanced E1’’s and/or a s and/or a

resolving power problem?resolving power problem?

–– 218218Ra B(E1, 11Ra B(E1, 11--)=4.10)=4.10--3 3 W.uW.u..

If we use this value and supposed that If we use this value and supposed that the B(E2) are equivalent to the one the B(E2) are equivalent to the one

in the in the gsbgsb we find :we find :

–– For For 230230U U I(E2)/I(E1)= 4.2%I(E2)/I(E1)= 4.2%–– For For 230230Th Th I(E2)/I(E1)= 1.4%I(E2)/I(E1)= 1.4%

This is highly improbable, that This is highly improbable, that one could not observed such one could not observed such transitions and, it is incoherent transitions and, it is incoherent that the ratio is bigger for that the ratio is bigger for 230230U U (no E2 reported)!(no E2 reported)!


SummarySummary

•• Tetrahedral Fingerprints:Tetrahedral Fingerprints:–– Rotational bands without E2Rotational bands without E2’’s for pure symmetrys for pure symmetry–– Vanishing QVanishing Q22

–– Branching ratios are spin dependent Branching ratios are spin dependent (difference with usual octupole)(difference with usual octupole)

•• First experimental results on First experimental results on 156156Gd: Gd: fully fully compatible with the abovecompatible with the above

•• Emphasising the actinide region, where there Emphasising the actinide region, where there exist signs of purer symmetry and shape exist signs of purer symmetry and shape coexistencecoexistence


ConclusionConclusion

It is urgent to have direct measurement of It is urgent to have direct measurement of the the absolute values of quadrupole and absolute values of quadrupole and

dipole momentsdipole moments of the tetrahedral of the tetrahedral candidates through lifetime measurementscandidates through lifetime measurements

(here lies the real smoking gun!)(here lies the real smoking gun!)and compare them with the other negative and compare them with the other negative

parity bands in the various regions of parity bands in the various regions of interestinterest


List of main collaboratorsList of main collaborators

D. Curien, J. Dudek, J. Robin, Ch. Beck, S. Courtin, O. Dorvaux, G. Duchêne, T. Faul,B. Gall, F. Haas, F. Khalfallah, H. Molique, M. Rousseau, MD Salsac - IPHC, Strasbourg D. Guinet, N. Redon, Ch. Schmitt, O.Stezowski, Q.D. Tuyen,- IPN, LyonP.T. Greenlees, P. Jones, R. Julin, S. Juutinen, S. Ketelhut, M. Nyman, P. Rahkila,J. Sorri, M. Leino, C. Scholey, J. Saren, U. Jakobsson, J. Uusitalo - JYFL, JyvaskylaF. Azaiez, B. Berthier, D. Guillemaud-Mueller, M. Leblois, F. Ibrahim, C.Petrache, D. Verney - IPN, OrsayA. Astier, I. Deloncle, G. Georgiev- CSNSM, OrsayN.Dubray - CEA, Bruyères-le-ChâtelR. A. Bark, J F. Sharpey-Schafer - iTHemba, Cape-TownJ. Gerl- GSI, DarmstadtB. Lauss, J. Jentschel, W. Urban -ILL,GrenobleD. Tonev - Bulgarian Academy of Sciences, SofiaL. Riedinger (and the US collaboration), N. Schunck - University of TennesseeD.J. Hartley - US Naval Academy, AnnapolisP. Bednarczyk, B. Fornal, A. Maj, K. Mazurek, K. Zuber- IFJ-PAN, KrakowG. de Angelis, A. Gadea - INFN, LegnaroR.P. Singh, S. Muralithar, R. Kumar, A. Jhingan, J.J. Das, R. K. Bhowmik - IUAC, New Delhi 67J. Dobaczewski, P. Olbratowski- Warsaw UniversityA. Gozdz, A. Dobrowolski - University of LublinY. R. Shimizu - Kyushu University, Fukuoka

And more!And more!

Thank you!Thank you!

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Search for Fingerprints of Tetrahedral Symmetry in the Rare …lea-colliga/public-docs/2008MeetingCatania/Monday… · Search for Fingerprints of Tetrahedral Symmetry in the Rare