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The Table of Nuclear Magnetic Dipole and Spectroscopic Electric Quadrupole Moments. Nick Stone IAEA Nuclear Data Meeting, Vienna, March 2011 • Status of Table/Compilation • Brief summary of active methods and recent results Next step: standards and recommended values Nuclear 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 1 neutron charge 0 Collective - whole nucleus charge Z/A valence nucleons - variable Spin angular momentum Single particle - proton s1/2 moment + 2.79 n.m. neutron s1/2 moment -1.91 n.m. A sensitive, non-quantised, measure of state wavefunctions Nuclear 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 density The Intrinsic quadrupole moment [for small eccentricity e = (1 - b2/a2))] is given by Q0 = 2/5 ZRm2e(1 + 2e/3) where the mean radius is Rm3 = ab2 And the largest measurable value of this is the Spectroscopic quadrupole moment. Qs = Q0[2I + 1)/(2I + 2)] For a PROLATE ellipsoid (a > b, football shape) Q0 is positive For an OBLATE ellipsoid (a < b, cushion shape) Q0 is negative A sensitive, non-quantised, measure of nuclear shape Reported compilation status 2009 • • • Moment measurements continue to be a vigorous area of nuclear research, providing detailed data for nuclear model development and testing Printed Table appeared in ADNDT in 2005. Succeeded Raghavan 1989. 2005 Table is out-of-date.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 – NSR • Recommended Value Table is straightforward for many entries. Some policy questions. • Approved for action starting 2011 • Consultation available in all cases from NJS. • Still true Updated Table Summary of additions and regions of recent activity Excel spreadsheet for late 2005 5701 lines [ 6 months after published version] Update to end 2010 Entries last isotope in 2010 in this range 1-500 501-1000 1001-1500 1501-2000 2001-2500 2501-3000 3001-3500 3501-4000 4001-4500 4501-5000 5001-5500 5500-6133 40Ar 63Zn 87Rb 95Ru 113Sn 141Xe 151Pm 160Dy 174Hf 191Pt 196Pb 254Es 6133 lines line entry of same isotope in 2005 431 831 1283 1696 2164 2627 3123 3620 4115 4597 5069 5701 new entries total this region 69 169 217 304 336 373 377 380 385 403 431 432 69 100 48 87 32 37 4 2 5 18 28 1 Wide 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-NMR ns excited states in fission fragments by recoil substitution into iron [IPAC] Cu ground states towards N = 78 by Laser, LTNO and Beta-NMR methods At least 80% of new results are for ground states: Techniques beta – NMR originally only below about A ~ 20, now up to A ~ 70 with fragmentation accelerators [e.g MSU] Laser spectroscopy ever more efficient for weaker beams, new ion sources allow extension to more refractory elements On-Line nuclear orientation few new results Far fewer new results for excited states Techniques longer lifetime [ms, ms, ns] shorter lifetime [ps] Why? PAC, TDPAD, etc Transient Field, RIV Loss of accelerators for stable beams Limited applicability of old methods half-life, count rate, angular distribution needed. Future experimental prospects Long-lived Laser and beta-NMR methods dominate ground state moment studies however these are finite in number lack of activity in lanthanide region – large ranges measured Shorter lived Numbers of known ms, ms, ns isomers grows slowly For ps states no really general method: limited accuracy TF needs large count rates and strong anisotropies – stable beams calibration is a problem applicable to states of lower spin [2, max ~ 4?] RIV only gives magnitude – where t known can it be calibrated without previous examples? Tough Innovation required!! To 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. Magnetic 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 D66 010001 (02)] Principle secondary standards are: 23Na, 165Ho, 185,187Re, 203,205Tl 207Pb 209Bi From these other standards are derived by ratio to give a complete reference structure throughout the periodic table. 199Hg, Gustavsson and Martensson-Pendrill reviewed the status of knowledge of these secondary standards [PR A58 3611 (1998)] - little change since but the more precise older moments based on earlier values will require adjustment. Nuclear 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 the measured 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 various approximations. Increases with Z reaching ~ 2% for Bi [Johnson et al ADNDT 28 333 (83)] b) any chemical shift caused by action of the applied field on the surrounding molecules. Hard to calculate, estimated uncertainty 1 in 103. [Gustavsson and Martensson-Pendrill PRA 58 3611 (98)] [Recent work of Jaszunski et al. to be published] These provide the basic standards for nuclear magnetic moments 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? 1. For some light nuclei theory can make accurate prediction - but this is rare! 2. Increased precision gives access to more sensitive phenomena e.g. for hydrogen like systems hyperfine interactions can probe QED effects which reach 0.5% for heavier elements. To provide a critical test of QED requires the moment to be known to higher precision than this. 2. 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-Weisskopf Effect or Hyperfine Anomaly]. This involves the distribution of nuclear magnetism within the nucleus and variation of the field over the nuclear volume. The correction can be as large as 10% but is more usually 0.l - 1%. In metals, the Knight shift which describes polarisation of the conduction electrons and the field they produce at the nucleus. Such measurements are NOT the basic standards of nuclear moment determination but require correction for the latest field value. Electric 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 nucleus THE EFG IS NEVER DIRECTLY MEASURED Muon wavefunction clean calculation of efg few light elements Na, Mg, Al, Cu, As, Nb, Pd almost all above ~ Sm Since ~ 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 differences from previous ‘best values’ in elements where there were no muonic data. Examples related to recent (since ~ 2000) atomic efg calculations 14N 19F (197 keV) Table entries Atomic efg results +0.02001(10) +0.02044(3) +2%, error down -0.121(5) [also -0.072(4) -0.0942(9) -21 or +31% +0.150(6) +0.146.6(10) error down 27Al Mu-X 49Ti +0.24(1) and +0.324(3) +0.247(11) -31% 63Cu Mu-X -0.211(4) -4% error down 69Ga +0.1650(8) and +0.171(11) 73Ge -0.220(15) +173(3) -0.17(3) +15% +3% or -5.5% +0.254(6) and +0.276(4) +0.261.5(2.5) 91Zr -0.206(10) and -0.257(13) -0.176(3) 131Xe Pb -0.360(40) -0.556(24) N.B.also ‘solid state’ calc -0.669(15) -0.120(12) and better error down -0.196(6) 81Br 121Sb +1 or 5%, -0.117(6) -15% or -32% +54% even larger good No muonic data: Q’s related to B(E2) in 4027 keV trans in 206Pb.[1979-2004] Situation: calculated efgs atomic and molecular wavefunctions (light and medium nuclei) and mesonic atom (heavier nuclei) now provide a systematic consistent basis for electric quadrupole moment measurements for many elements to precision of a few %. Many present Table entries still rely on older efg estimates, and/or old B[E2] values The time is clearly ripe for a review of all quadrupole moments! Conclusions Plan of action: 1. Continue to update new entries at 12 month intervals. Publish update frequency ---- 3 to 5 years? 2. Attack need for recommended values by a) review of standards, followed by b) appropriate reanalysis in the light of revised standards – including Fuller listings c) averaging of results to obtain ‘best values’. Thank you 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 is rare! 2. Increased precision gives access to more sensitive phenomena e.g. for hydrogen like systems hyperfine interactions can probe QED effects which reach 0.5% for heavier elements. To provide a critical test of QED requires the moment to be known to higher precision. Current activity: recommended values • What's involved ? • Magnetic dipole moments: – – – – Basic NMR ratios The diamagnetic correction Hyperfine anomalies The Knight shift • Electric quadrupole moments: – Basic NMR ratios – The Sternheimer correction 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 is rare! 2. Increased precision gives access to more sensitive phenomena e.g. for hydrogen like systems hyperfine interactions can probe QED effects which reach 0.5% for heavier elements. To provide a critical test of QED requires the moment to be known to higher precision. Recoil in Vacuum In 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 ion It is established that magnetic effects are dominant, thus the attenuation was a measure of the g-factor [g = magnetic moment m / spin I ] of the decaying nuclear state. This is the basis of the Recoil In Vacuum [RIV] method of gfactor determination [see e.g. Broude, Goldring et. al. NPA215 617 (1973)]. Recoil in Vacuum Target Foil Total angular momentum F Target recoil Beam Coulex Recoil Nuclear spin 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 attenuated Brief description of the recent RIB 132Te RIV measurement at HRIBF [N.J.Stone et al PRL 94 192501 (2005)] UNATTENUATED Distribution for 126Te stopped in Cu. RIV ATTENUATED distributions from 2+1 states in 122,126,130Te [known g-factors and lifetimes]. W ( , ) Gk kq Ak Qk D ( , ,0) k* q k .q Gk are the g-factor dependent attenuation coefficients. For the RIV method we need to extract g from the Gk. Compared 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| 2+1 132Te = 0.35(5). N.B. ps lifetime Plotted curves are result of empirical 'theory' with fitting parameter to stable isotope results - not an a priori theory. New 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 lifetimes Calibration 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. Can we hope to provide a sound theoretical grounding for the CALIBRATION OF RIV ATTENUATIONS? The problem In 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. Ground State Magnetic Moments of Cu isotopes [Lifetime range: stable - ms] Methods On-Line Nuclear Orientation with NMR/ON Fragment polarisation allied to beta-NMR In-source Laser spectroscopy High resolution collinear laser spectroscopy Objectives Full study of moments between major shell closures N = 28 - N = 40 for single proton beyond Z = 28 Towards establishing reliable nuclear models for the region of N = 50 [A = 78] - R process importance Pre 1998 Only three, mid-shell, values known: isotopes 63,65Cu are stable 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 J. Rikovska-Stone et al. PRL 85 1392 (2000) (Schmidt limit) and based on full treatment of moment operator, including meson exchange, gave value 2.85 n.m. At 28,40 double shell closure: Full agreement with best shell model theory [calculations by Ian Towner] [J.Rikovska et al. PRL 85 1392 (2000)] Down to shell closure at N = 28 59Cu measured by Leuven group at NICOLE by On-Line NMR/ON m(59Cu, 3/2-) = 1.891(9) n.m. [V.V.Golovko et al. PR C70 014312 (2004)] 57Cu measured by b-NMR at MSU fragment separator m(57Cu, 3/2-) = 2.00(5) n.m [K.Minamisono et al. PRL 98 103508 (2006)] N.B. Narrow resonance p3/2 proton moments across full sub-shell N = 28 - 40 First complete shell - shell sequence BUT 57Cu result shows little sign of predicted return to close to the value found for 69Cu Major discrepancy with shell model theory. Is 56Ni truly double magic? On-Line Laser spectroscopy Collinear and In-Source Methods In Source, Doppler width resolution ~ 250 MHz 68Cu Collinear Concept - add constant energy to ions ΔE=const=δ(1/2mv2)≈mvδv Resolution ~ 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) PR C77 067302 (2008) 63Cu m = 2.22(9) n.m. [Ref 2.23] 59Cu m = 1.84(3) n.m. [Ref. 1.89] 58Cu 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. •5/2- level associated with the π(f5/2) orbital E(keV) 1000 1/25/2- ? 57 59 61 63 65 67 69 71 73 75 Mass number S. Franchoo et al. Phys. Rev. C 64 054308 I. Stefanescu Phys. Rev. Lett 100 (2008) A.F. Lisetskiy et al. Eur. Phys. J. A, 25:95, 2005 N.A. Smirnova et al. Phys. Rev. C, 69:044306, 2004 I=5/2- level: •Remains static between 57-69Cu at ~1MeV •Systematically drops in energy as the ν(g9/2) shell begins to fill •Predictions on the inversion of the ground state lie between 73Cu and 79Cu. •Experimental evidence for the inversion to occur at 75Cu. From Kieren Flanagan The 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 Magnetic moments A > 70 71Cu 73Cu 77Cu NMR/ON I = 3/2 m = 2.28(1) n.m. collinear laser I = 3/2 m = 1.748(1) n.m. [Isolde laser group, unpublished] in-source laser I = 5/2 m = 1.75(5) n.m. [in-source laser group, unpublished] In source laser data, 75Cu, fits for I = 3/2,5/2 Peaks barely resolved, but clear preference for spin 5/2 Moment 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. A > 71 71Cu 73Cu 75Cu 77Cu NMR/ON I = 3/2 m = 2.28(1) n.m. collinear laser I = 3/2 m = 1.748(1)* n.m. [Isolde laser group, to be published] in-source laser I = 5/2 m = 1.005(1)* n.m. and collinear laser [combined group, to be published] in-source laser I = 5/2 m = 1.75(5)* n.m. [in-source laser group, to be published] * preliminary values Overall situation: ground state spin change positively identified at A = 75 Schmidt limit for f5/2 is at +0.8 n.m. STOP 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] The Final Picture Conclusions 1. 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. Moment measurements in Fission Fragments - towards the neutron drip-line Methods involving rotation of angular correlation of gamma transitions in a polarised iron foil [Manchester group - Gavin Smith et al.] and attenuation of angular correlation of gamma transitions in an unpolarised iron foil [Vanderbilt group - Goodin et al.] Both these give measurable effects for ns states Applied to recoiling fragments from 252Cf sample Huge data sets > 1011 multifold coincidences Table of Magnetic Dipole and Electric Quadrupole Static Nuclear Moments • History: Gladys Fuller ~ 1975 - very comprehensive Pramila Ragahavan 1989 ADNDS - older averaged NJS - Raghavan + listing of all published since » Started ~ 1998 setting up first spreadsheet electronic version » To publish - required retype as word document • Table published [after extended discussions Dunford/Raman]: – Atomic Data and Nuclear Data Tables N. J. Stone ADNDT 90 75 [2005]. • Contains all reported nuclear magnetic dipole moments and electric quadrupole moments of ground and excited states total ~ 4000 entries • available from [email protected] to late 2005. Further possible action: recommended values • What's involved ? • Magnetic dipole moments: – – – – Basic NMR ratios The diamagnetic correction Hyperfine anomalies The Knight shift • Electric quadrupole moments: – Basic NMR ratios – The Sternheimer correction – Best 'standards' discrepant at ~ 1% level It will take a considerable time to set up a matrix of interrelated standards throughout the nuclear chart. 178Hf is at the centre of the multi-quasiparticle K-isomer region skyscrapers 178Hf (109 s = 31 y) 2.4 MeV, 16ħ [Walker and Dracoulis, Hyp. Int. 135 (2001) 83] Isomers in 177,179,180,182,[184]Hf are long-enough lived to be accessible to Low Temperature On-Line Nuclear Orientation at the NICOLE facility.. 177Hf levels [Mullins et al., PRC58 (1998) 831] combination of measurements of m and d => gK and gR g-factors for deformed nuclei combination of both measurements => gK and gR single-particle properties collective properties => configurations and admixtures see, for example: Purry et al., NPA632 (1998) 229 El-Masri et al., PRC72 (2005) 054306 => neutron and proton pair quenching Magnetic moment 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.) gR values: 178Hf K=0 gR= 0.240(14) K=6 π2 gR= 0.35(5) K=16 π2ν2 gR= 0.28(4) more data needed, more-accurate data needed New Result 177Hf K=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]