Presentation on theme: "IAEA Nuclear Data Meeting, Vienna, March 2011"— Presentation transcript:
1IAEA Nuclear Data Meeting, Vienna, March 2011 The Table of Nuclear Magnetic Dipole and Spectroscopic Electric Quadrupole Moments.Nick StoneIAEA Nuclear Data Meeting, Vienna, March 2011Status of Table/CompilationBrief summary of active methodsand recent resultsNext step: standards and recommended values
2Nuclear magnetic dipole moment. Nuclear magnetism has contributions from all angular motion with unit the nuclear magneton (n.m.)Orbital angular momentum:Single particle proton charge 1neutron charge 0Collective whole nucleus charge Z/Avalence nucleons - variableSpin angular momentumSingle particle proton s1/2 moment n.m.neutron s1/2 moment n.m.A sensitive, non-quantised, measure of state wavefunctions
3Nuclear electric quadrupole moment. Measures the departure from sphericity of the nuclear charge distribution.Ellipsoidal shape with major axis a and minor axis b and uniform charge densityThe Intrinsic quadrupole moment [for small eccentricity e = (1 - b2/a2))] is given byQ0 = 2/5 ZRm2e(1 + 2e/3) where the mean radius is Rm3 = ab2And the largest measurable value of this isthe Spectroscopic quadrupole moment.Qs = Q0[2I + 1)/(2I + 2)]For a PROLATE ellipsoid (a > b, football shape) Q0 is positiveFor an OBLATE ellipsoid (a < b, cushion shape) Q0 is negativeA sensitive, non-quantised, measure of nuclear shape
4Reported compilation status 2009 Moment measurements continue to be a vigorous area of nuclear research, providing detailed data for nuclear model development and testingPrinted Table appeared in ADNDT in Succeeded Raghavan 1989.2005 Table is out-of-date. Needs some months of work to cover last 4 years. Longer to set up 'recommended values'.Done! Thanks to NDS, IAEA support. Table current to end 2010 now accessible through IAEA Nuclear Data website Livechart.Contact with ADNDT editor David Schultz established that update would be accepted by the journal.Supplement Table in preparation. IAEA Report – NSRRecommended Value Table is straightforward for many entries. Some policy questions.Approved for action starting 2011Consultation available in all cases from NJS.Still true
5Summary of additions and regions of recent activity Updated TableSummary of additions and regions of recent activityExcel spreadsheet for late lines[ 6 months after published version]Update to end linesEntries last isotope in 2010 line entry of same new entriesin this range isotope in total this regionArZnRbRuSnXePmDyHfPtPbEs
6Wide ranges of nuclei, lifetime and method RIB Te ps excited states by Recoil into Vacuum [IPAC]Hf K-isomers by On-Line Nuclear Orientation [OLNO]Beta-NMRns excited states in fission fragments by recoil substitution into iron [IPAC]Cu ground states towards N = 78 by Laser, LTNO and Beta-NMR methods
7At least 80% of new results are for ground states: Techniquesbeta – NMR originally only below about A ~ 20, now up to A ~ 70with fragmentation accelerators [e.g MSU]Laser spectroscopy ever more efficient for weaker beams, new ion sourcesallow extension to more refractory elementsOn-Line nuclear orientation few new resultsFar fewer new results for excited stateslonger lifetime [ms, ms, ns] PAC, TDPAD, etcshorter lifetime [ps] Transient Field, RIVWhy? Loss of accelerators for stable beamsLimited applicability of old methodshalf-life, count rate, angular distribution needed.
8Tough Innovation required!! Future experimental prospectsLong-livedLaser and beta-NMR methods dominate ground state moment studieshowever these are finite in numberlack of activity in lanthanide region – large ranges measuredShorter livedNumbers of known ms, ms, ns isomers grows slowlyFor ps states no really general method: limited accuracyTF needs large count rates and strong anisotropies – stable beamscalibration is a problemapplicable to states of lower spin [2, max ~ 4?]RIV only gives magnitude – where t knowncan it be calibrated without previous examples?Tough Innovation required!!
9To revert to nuclear data and the Tabulation Main interest is a need to offer ‘Recommended Values’ in addition to a listing of all published results.
10Magnetic Dipole Moments: The Standards The basic standards of nuclear magnetism are:The proton and the deuteron [values from Fundamental Physical Constants see e.g. PR D (02)]Principle secondary standards are:23Na, ,205Tl From these other standards are derived165Ho, Pb by ratio to give a complete reference structure185,187Re, Bi throughout the periodic table.199Hg,Gustavsson and Martensson-Pendrill reviewed the status of knowledge of these secondary standards [PR A (1998)] - little change since but the more precise older moments based on earlier values will require adjustment.
11Nuclear magnetic moment measurements can be divided into two categories: 1. Measurements involving an external applied magnetic field [uniform].NMR in liquids, gases. Atomic beam experiments [includes lasers]Optical pumping in atoms.In these methods, to extract the true nuclear dipole moment themeasured energy splitting has to be corrected for:a) the diamagnetic correction caused by the action of the applied field on the electrons. Calculated for neutral atoms in variousapproximations. Increases with Z reaching ~ 2% for Bi[Johnson et al ADNDT (83)]b) any chemical shift caused by action of the applied field on thesurrounding molecules. Hard to calculate, estimated uncertainty1 in 103. [Gustavsson and Martensson-Pendrill PRA (98)][Recent work of Jaszunski et al. to be published]These provide the basic standards for nuclear magnetic moments
12When are these small corrections important? Only for the most precise measurements is there a real problem in setting 'recommended values' for magnetic moments.For most the experimental error is larger than diamagnetic corrections and hyperfine anomalies.When are these small corrections important?For some light nuclei theory can make accurate prediction - but this is rare!2. Increased precision gives access to more sensitive phenomenae.g. for hydrogen like systems hyperfine interactions can probe QEDeffects which reach 0.5% for heavier elements. To provide a criticaltest of QED requires the moment to be known to higher precisionthan this.
132. Measurements involving internal fields [Hyperfine interactions in atoms and ions, hyperfine fields e.g in ferromagnetic metals.]NMR in magnetic materials, including ferromagnetic metals, where field at nucleus is dominated by local electrons.These are liable to corrections for:Variation in local field over the nuclear volume [Bohr-WeisskopfEffect or Hyperfine Anomaly].This involves the distribution of nuclear magnetism within thenucleus and variation of the field over the nuclear volume. Thecorrection can be as large as 10% but is more usually 0.l - 1%.In metals, the Knight shift which describes polarisation of theconduction electrons and the field they produce at the nucleus.Such measurements are NOT the basic standards of nuclear momentdetermination but require correction for the latest field value.
14Electric Quadrupole Moments: The Standards The basic standards have long been accepted as those from muonic atoms.Reason: Measure product Qs x electric field gradient (efg) at nucleusTHE EFG IS NEVER DIRECTLY MEASUREDMuon wavefunction clean calculation of efgfew light elements Na, Mg, Al, Cu, As, Nb, Pdalmost all above ~ SmSince ~ late 90’s challenged and supplemented by atomic hfs theorists[Bieron, Pyykko, Sundholm, Kello, Sadlej ……]Agreement between muonic and atomic results good only to a few %.New atomic results also lead to revised Q’s with serious differencesfrom previous ‘best values’ in elements where there were no muonic data.
15Examples related to recent (since ~ 2000) atomic efg calculations Table entries Atomic efg results14N (10) (3) +2%, error down19F (197 keV) (5) [also (4) (9) -21 or +31%27Al Mu-X (6) (10) error down49Ti +0.24(1) and (3) (11) -31%63Cu Mu-X (15) (4) -4% error down69Ga (8) and (11) (3) or 5%, error down73Ge (3) (6) +15%81Br (6) and (4) (2.5) +3% or -5.5%91Zr (10) and (13) (3) % or -32%121Sb (40) (24) +54%N.B.also ‘solid state’ calc (15) even larger131Xe (12) and better (6) goodPb No muonic data: Q’s related to B(E2) in 4027 keV trans in 206Pb.[ ]
16The time is clearly ripe Situation: calculated efgsatomic and molecular wavefunctions (light and medium nuclei) andmesonic atom (heavier nuclei)now provide a systematic consistent basis for electric quadrupole moment measurements for many elementsto precision of a few %.Many present Table entries still rely on older efg estimates, and/or old B[E2] valuesThe time is clearly ripefor a review of allquadrupole moments!
17Conclusions Plan of action: 1. Continue to update new entries at 12 monthintervals. Publish update frequency to 5 years?Attack need for recommended values bya) review of standards, followed byb) appropriate reanalysis in the light of revisedstandards – including Fuller listingsc) averaging of results to obtain ‘best values’.
19Why are these small corrections important? Only for the most precise measurements is there a real problem in setting 'recommended values' for magnetic moments.For many the experimental error is larger than such considerations as diamagnetic corrections and hyperfine anomalies.Why are these small corrections important?1. For some light nuclei theory can make accurate prediction - but this israre!2. Increased precision gives access to more sensitive phenomenae.g. for hydrogen like systems hyperfine interactions can probe QEDeffects which reach 0.5% for heavier elements. To provide a criticaltest of QED requires the moment to be known to higher precision.
21Why are these small corrections important? Only for the most precise measurements is there a real problem in setting 'recommended values' for magnetic moments.For many the experimental error is larger than such considerations as diamagnetic corrections and hyperfine anomalies.Why are these small corrections important?1. For some light nuclei theory can make accurate prediction - but this israre!2. Increased precision gives access to more sensitive phenomenae.g. for hydrogen like systems hyperfine interactions can probe QEDeffects which reach 0.5% for heavier elements. To provide a criticaltest of QED requires the moment to be known to higher precision.
22Recoil in VacuumIn the late 1960's it was found that when ions emerge from a target after excitation by Coulomb excitation and enter vacuum, the angular properties of their decay gamma radiations are perturbed.The anisotropy of the angular distribution is attenuated.The attenuations are determined by the precession of the excited state nuclear spin in the hyperfine interaction of the ionIt is established that magnetic effects are dominant, thus the attenuation was a measure of theg-factor [g = magnetic moment m / spin I ]of the decaying nuclear state.This is the basis of the Recoil In Vacuum [RIV] method of g-factor determination [see e.g. Broude, Goldring et. al. NPA (1973)].7g-factor [g = magnetic moment m / spin I ]
23Recoil in Vacuum Target Foil Total angular momentum F Target recoil In vacuum, recoiling ion electron angular momentum J has random direction. Recoiling Coulex nuclear spin I, initially aligned in plane of target, precesses about resultant F=I+J.Anisotropy of angular distribution of decay gamma emission becomes attenuatedTotal angular momentum FTarget recoilBeamCoulex RecoilNuclear spin
24Brief description of the recent RIB 132Te RIV measurement at HRIBF [N.J.Stone et al PRL (2005)]UNATTENUATED Distribution for 126Te stopped in Cu.RIV ATTENUATED distributions from 2+1 states in 122,126,130Te [known g-factors and lifetimes].Gk are the g-factor dependent attenuation coefficients.For the RIV method we need to extract g from the Gk.
25Compared unattenuated with attenuated to obtain G2, G4 from isotopes with known g-factors and lifetimes t to form calibration for their gt dependence.Result: |g-factor| Te = 0.35(5). N.B. ps lifetimePlotted curves are result of empirical 'theory' with fitting parameter to stable isotope results - not an a priori theory.
26New Opportunities and challenges for the study of ps state g-factors: RIB's having beam intensity < 108 ions/s - orders of magnitude weaker than conventional beams.With the advent of RIB's and inevitable poorer statistics the RIV method offers prospects of useful g-factor study for ps lifetimesCalibration as for the Te 2+ states not possible for other spins and odd-A isotopes - too few measured g-factors exist. An a priori approach is required.The problemIn principle the recoiling ion is an attractive system for theoretical approach. The number of electrons is fixed [neglecting Auger effects] and the physics is fully understood [Coulomb] although complex.Can we hope to provide a sound theoretical grounding for the CALIBRATION OF RIV ATTENUATIONS?
27Ground State Magnetic Moments of Cu isotopes [Lifetime range: stable - ms]MethodsOn-Line Nuclear Orientation with NMR/ONFragment polarisation allied to beta-NMRIn-source Laser spectroscopyHigh resolution collinear laser spectroscopyObjectivesFull study of moments between major shell closures N = N = 40 for single proton beyond Z = 28Towards establishing reliable nuclear models for the region of N = 50 [A = 78] - R process importance
28Pre 1998Only three, mid-shell, values known: isotopes 63,65Cu are stable
29Magnetic moment 69Cu(3/2-) = 2.84(1) n.m. 1999 Cu Laser ion source at ISOLDE : 67,69Cu moments measured by NMR/ON at NICOLE on-line nuclear orientation facility, ISOLDE, CERN using the new laser Cu ion source.Magnetic moment 69Cu(3/2-)= 2.84(1) n.m.Starting from extreme single particle (Schmidt limit) and based on full treatment of moment operator, including meson exchange, gave value 2.85 n.m.J. Rikovska-Stone et al. PRL (2000)At 28,40 double shell closure: Full agreement with best shell model theory [calculations by Ian Towner][J.Rikovska et al. PRL (2000)]
30Down to shell closure at N = 28 59Cu measured by Leuven group at NICOLE by On-Line NMR/ONm(59Cu, 3/2-) = 1.891(9) n.m. [V.V.Golovko et al. PR C (2004)]57Cu measured by b-NMR at MSU fragment separatorm(57Cu, 3/2-) = 2.00(5) n.m [K.Minamisono et al. PRL (2006)]N.B. Narrow resonance
31p3/2 proton moments across full sub-shell N = 28 - 40 First complete shell - shell sequence BUT57Cu result shows little sign of predicted return to close to the value found for 69CuMajor discrepancy with shell model theory. Is 56Ni truly double magic?
32On-Line Laser spectroscopy Collinear and In-Source Methods In Source, Doppler width resolution ~ 250 MHzCollinear Concept - add constant energy to ions68CuΔE=const=δ(1/2mv2)≈mvδvResolution ~ MHz, resulting from the velocity compression of the line shape through energy increase.In Cu+ ion, electron states involved are s1/2 and p1/2.With nuclear spin I these each form a doublet with F (= I + J) = I +1/2 and I - 1/2.Transitions between these doublets give four lines in two pairs with related splittings.- can be fitted with poor resolution only for the A (magnetic dipole) splitting and in good resolution, for both A and B (electric quadrupole splitting)
33Measurement of moment of 58Cu (I = 1) at ISOLDE: PR C (2008)63Cu Cu Cum = 2.22(9) n.m. [Ref 2.23] m = 1.84(3) n.m. [Ref. 1.89] m = 0.52(8) n.m.Measurement of moment of 58Cu (I = 1) at ISOLDE:Established fitting parameters using data on 63Cu, confirmed by 59 Cu fit agreement with previous NMR/ON result.58Cu [odd-odd] predictions - based on shell model 57Cu 0.68(1) n.m based on MSU 57Cu result 0.40(2) n.m.Nature not kind: experimental result 0.52(8) n.m. no decisive answer.
345/2- level associated with the π(f5/2) orbital I=5/2- level:Remains static between 57-69Cu at ~1MeVSystematically drops in energy as the ν(g9/2) shell begins to fillPredictions on the inversion of the ground state lie between 73Cu and 79Cu.Experimental evidence for the inversion to occur at 75Cu.5/2- level associated with the π(f5/2) orbitalE(keV)10001/2-5/2-?57596163656769717375Mass numberS. Franchoo et al. Phys. Rev. CI. Stefanescu Phys. Rev. Lett 100 (2008)A.F. Lisetskiy et al. Eur. Phys. J. A, 25:95, 2005N.A. Smirnova et al. Phys. Rev. C, 69:044306, 2004From Kieren Flanagan
35The relative intensity of the two (unresolved doublet) peaks in the In-Source method is related to the nuclear spin through the statistical weight (2F + 1)Fitted data for 77Cu for I = 3/2 and I = 5/'2 - clearly favours 5/2 assignment.N.B. peaks well resolved
36Magnetic moments A > 70 71Cu NMR/ON I = 3/2 m = 2.28(1) n.m.73Cu collinear laser I = 3/2 m = 1.748(1) n.m.[Isolde laser group, unpublished]77Cu in-source laser I = 5/2 m = 1.75(5) n.m.[in-source laser group, unpublished]
37In source laser data, 75Cu, fits for I = 3/2,5/2 Peaks barely resolved, but clear preference for spin 5/2Moment of 75Cu(I = 5/2) m = 0.99(4) n.m. [Aug 2008]Confirmed during collinear run, later Aug 08, which used the in-source moment to set line search frequencies.
38A > 7171Cu NMR/ON I = 3/2 m = 2.28(1) n.m.73Cu collinear laser I = 3/2 m = 1.748(1)* n.m.[Isolde laser group, to be published]75Cu in-source laser I = 5/2 m = 1.005(1)* n.m.and collinear laser[combined group, to be published]77Cu in-source laser I = 5/2 m = 1.75(5)* n.m.[in-source laser group, to be published]* preliminary values
39Overall situation: ground state spin change positively identified at A = 75 Schmidt limit for f5/2 is at +0.8 n.m.
40STOP PRESS UPDATE!!! Isolde Feb 16th MSU result for 57Cu is WRONG. New data from Leuven show resonance at higher frequency.New [est N.J.S.] value 57Cu m = 2.6(1) n.m.[Cocolios, Van Duppen et al. to be published]
42Conclusions1. Shell model has managed to calculate odd-A magnetic moments at N = 28, 40 very well and between them adequately.2. Now that shift of the f5/2 state has been identified, magnetic moments of 75,77Cu should be calculated reasonably well. This residual interaction effect is established.3. Models which give these results successfully may be expected to give useful predictions concerning the A = 78 shell closure. Others which fail to reproduce these may not be trusted in other predictions.The magnetic moments are a valuable constraint.
43Moment measurements in Fission Fragments - towards the neutron drip-lineMethods involvingrotation of angular correlation of gamma transitions in a polarised iron foil [Manchester group - Gavin Smith et al.]andattenuation of angular correlation of gamma transitions in an unpolarised iron foil [Vanderbilt group - Goodin et al.]Both these give measurable effects for ns statesApplied to recoiling fragments from 252Cf sampleHuge data sets > 1011 multifold coincidences
48Table of Magnetic Dipole and Electric Quadrupole Static Nuclear Moments History: Gladys Fuller ~ very comprehensivePramila Ragahavan 1989 ADNDS - older averagedNJS - Raghavan + listing of all published sinceStarted ~ 1998 setting up first spreadsheet electronic versionTo publish - required retype as word documentTable published [after extended discussions Dunford/Raman]:Atomic Data and Nuclear Data TablesN. J. Stone ADNDT .Contains all reported nuclear magnetic dipole moments and electric quadrupole moments of ground and excited states total ~ 4000 entriesavailable from to late 2005.
49Further possible action: recommended values What's involved ?Magnetic dipole moments:Basic NMR ratiosThe diamagnetic correctionHyperfine anomaliesThe Knight shiftElectric quadrupole moments:The Sternheimer correctionBest 'standards' discrepant at ~ 1% levelIt will take a considerable time to set up a matrix of interrelated standards throughout the nuclear chart.
52skyscrapers178Hf is at the centre of the multi-quasiparticle K-isomer region178Hf (109 s = 31 y)2.4 MeV, 16ħ[Walker and Dracoulis, Hyp. Int. 135 (2001) 83]Isomers in 177,179,180,182,Hf are long-enough lived to be accessible to Low Temperature On-Line Nuclear Orientation at the NICOLE facility..
53177Hf levels combination of measurements of m and d => gK and gR [Mullins et al., PRC58 (1998) 831]combination of measurements of m and d=> gK and gR
54g-factors for deformed nuclei combination of both measurements=> gK and gRsingle-particle propertiescollective properties=> configurations and admixturessee, for example:Purry et al., NPA632 (1998) 229El-Masri et al., PRC72 (2005)=> neutron and protonpair quenching
55Moment value: 7.33(7) n.m. (est. 8.14(17) n.m.) Magnetic momentThis graph shows the 177 Hf 37/2- isomer resonance centred at MHz. The y axis represents the combined signal from several transitions in the decay of this isomer.The central frequency v0 together with the known hyperfine field of Hf in Fe was used to determine the magnetic moment of the 37/2 isomer.It is lower than the estimated value, showing the limitation of the method used to obtain the estimates and the importance to exact measurement.NMR/ON observed in a combined signal from several transitions from the upper, 37/2− isomer.Moment value: 7.33(7) n.m. (est. 8.14(17) n.m.)55
56gR values: 178Hf New Result 177Hf K=37/2 p2n3 gR=0.22(3) K= gR= 0.240(14)K=6 π2 gR= 0.35(5)K=16 π2ν2 gR= 0.28(4)more data needed, more-accurate data neededNew Result 177HfK=37/2 p2n3 gR=0.22(3)[K = 23/2 p2n1 accessible when moment measured.][K=6, 16: Mullins et al., Phys. Lett. B393 (1997) 279]