Results from the collinear laser spectroscopy collaboration at ISOLDE-CERN

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1 Results from the collinear laser spectroscopy collaboration at ISOLDE-CERN Gerda Neyens K.U. Leuven: K. Flanagan, D. Yordanov, P. Lievens, G. Neyens, M. De Rydt, P. Himpe, N. Vermeulen. Universität Mainz: K. Blaum, M. Kowalska, R. Neugart, W. Northerhauser, C. Geppert The University of Manchester: J. Billowes, P. Campbell, B. Cheal

2 Laser-related measurements of moments and radii From Kluge & Nörtershäuser 2003 Present physics goals: Monopole migration of single particle levels: - isotopes (Z=29) - Ga isotopes (Z=31) The island of inversion: A region of nuclei with a ground state dominated by particle-hole excitations of neutrons across N=20 shell gap! Competition between 0p0h, 1p1h and 2p2h configurations

3 Laser-related measurements of moments and radii From Kluge & Nörtershäuser 2003 Developments: Monte Carlo simulation model based on real physics input, to simulate β-asymmetry and optical hyperfine structure spectra from polarized beams induced by multi-step resonant ionization induced by optical pumping Goal: extract δ<r 2 > from β-asymmetry detected HFS

4 10 7 COLLAPS set-up at ISOLDE: - collinear laser spectroscopy with optical detection spin, magnetic moment, quadrupole moment, charge radii Advantages: high resolution, no upper limit on lifetime Disadvantage: need ions/µc (best achieved 70 )! yields In-source Photon counters collinear Ion beam Laser beam

5 COLLAPS set-up at ISOLDE: - collinear laser spectroscopy with β-asymmetry detection on an optically polarized radioactive beam (t 1/2 < few s) spin, magnetic moment, quadrupole moment understand line shapes to extract charge radii!! Advantages: need only few 10 3 ions/µc! Disadvantage: upper lifetime limit (~ few seconds) to extract charge radii need to understand line shapes from polarized beam β-asymmetry detection (never done) E e ~ B(Q) E g = A(g)(I+1/2) β-asymmetry(%) 33 Mg + (I=3/2) 33 Mg, HFS Ion beam β-counters Relative laser frequency (MHz) Laser beam

6 COLLAPS set-up at ISOLDE: - β-nuclear magnetic resonance with β-asymmetry detection on an optically polarized radioactive beam (t 1/2 < few s) implanted in a crystal, immersed in a magnetic field g-factor, quadrupole moment Advantages: need only few 10 3 ions/µc, very high precision (< 10-3 )! Disadvantage: upper lifetime limit (~ few seconds) I=3/2 ηω L Zeeman splitting m=3/2 m=1/2 m=-1/2 m=-3/2 β-asymmetry(%) 33 Mg, NMR Ion beam RF-frequency (khz) β-counters Laser beam

7 Measurements on Mg ions: from A=24,25,26 (stable) to A=27,29,31,33 (beyond N=20 shell gap) photon counts HFS 25 Mg 1+ I=5/2 Use as calibration for hyperfine fields -3A gr Yields > 10 7 ions/puls photon counts HFS 27 Mg 1+ I=1/2 -A gr g( 27 Mg) = g( 25 Mg) A( 27 Mg)/A( 25 Mg) sign of g and spin follow from shape of HFS g = (33) I = 1/2 Ground state spin confirmed Magnetic moment consistent with sd-shell model Kowalska, Yordanov et al., in preparation

8 Measurements on Mg ions: from A=24,25,26 (stable) to A=27,29,31,33 (beyond N=20 shell gap) Hyperfine Structure 33 Mg in MgO Yield ~ ions/puls β-nmr g = (3) ~ g(i+1/2) Unambiguous determination of 33 Mg spin I = 3/2 and parity negative!! g = (3) pure 2p2h intruder state! Yordanov et al.,in preparation

9 Measurements on Mg ions: conclusions (1) Mg isotopes up to 29 Mg normal ground state structure (good agreement with sd shell model, USD interaction) (2) 31 Mg and 33 Mg pure 2p2h intruder ground state configurations (sd-pf shell model) 31 Mg (Z=12, N=19) I π =1/ Mg (Z=12, N=21) I π = 3/2-2p 3/2 1f 7/2 20 pf 2p2h 2p 3/2 1f 7/2 20 pf 2p2h 1d 3/2 1d 3/2 2s 1/2 sd 2s 1/2 sd 1d 5/2 ν 8 1d 5/2 ν 8 (νd -3 3/2 ) 1/2+ (νf 7/2 νs 1/2 3 ) 3/2- νp 3/2

10 Measurements on Mg ions: conclusions (1) Mg isotopes up to 29 Mg normal ground state structure (good agreement with sd shell model, USD interaction) (2) 31 Mg and 33 Mg pure 2p2h intruder ground state configuration (sd-pf shell model) (3) New spin assignments to lowest levels in 31 Mg and 33 Mg rotational bands build on ½+[200] and on 3/2-[321] 31 Mg 33 Mg Yordanov et al.,in preparation

11 53 Measurements on ions: from A=63,65 (stable) to A= 64,66,67,68,69,70 (beyond N=40 shell gap) ISOLDE data base values August 2006 yield September 2006 yield Fluorescence detection limit Yields > 10 6 ions/puls Measured up to 70 Up to 74 possible with present method

12 Measurements on ions: from A=63,65 (stable) to A= 64,66,67,68,69,70 (beyond N=40 shell gap) RESULTS (1) Quadrupole moments stiffness of the 68 core, proton effective charge from Q( ) polarizability of the core Odd isotopes: proton in πp3/2 orbit Q( 69 2j-1 ) Q sp (πp 3/2 ) = e eff <r 2 > 2j (13) efm 2 determine proton effective charge Q(N)/Q(N=40) Q(N)/Q(N=126) Bi Flanagan et al.,in preparation

13 Measurements on ions: from A=63,65 (stable) to A= 64,66,67,68,69,70 (beyond N=40 shell gap) RESULTS (1) Quadrupole moments (2) Inversion of the sign of the magnetic moment from 64 to 66 observed gives information of mixing with νp1/2 (νp1/2 monopole migration) Odd-odd isotopes: πp3/2 coupling to νp3/2 58,60 (N=29-31) νf5/2 62,64,66 (N=33-37) νp1/2 68 (N=39) 66, I π =1 + 3 µ πp 3/2 νp 1/ µ n 2 68g +2.48(2)µ n 64, I π =1 + 1 Flanagan et al.,in preparation (2)µ n due to νp 1/ (2)µ n πp 3/2 νf 5/ µ n

14 Measurements on ions: from A=63,65 (stable) to A= 64,66,67,68,69,70 (beyond N=40 shell gap) RESULTS (1) Quadrupole moments (2) Inversion of the sign of the magnetic moment from 64 to 66 observed (3) Isomer shift in 68 and isotope shifts from (4) High precision on all magnetic moments (improved 1-2 orders at least) (5) Sign confirmation of 70g and 68g,m magnetic moment.

15 FUTURE MG ISOTOPES Measure isotope shifts compare static charge radii with radii from B(E2) (influence of 2 + deformation) from β-asymmetry detection need high precision (~ khz) / line shape analysis! FIRST ATTEMPT (K. Flanagan, based on S. Gheysen, PRC (2004)) Construct Hamiltonian of system under consideration (dressed state approach,) Diagonalization of Hamiltonian via cyclic Jacobi method to find atom-plus-field dressed states Calculate the probability of remaining in state i at time t after the interaction is switched on (t=0) 4. Use monte carlo techniques + model to simulate polarization/ionization spectra.

16 FUTURE MG ISOTOPES Measure isotope shifts compare static charge radii with radii from B(E2) (influence of 2 + deformation) from β-asymmetry detection need high precision (~ khz) / line shape analysis! Simple check against real data: fluorescence detection from 65 The model includes: Laser intensity Ion rate Voigt profile Hyperfine transition rate equation (Runge Kutta integration) Optical pumping distance.

17 FUTURE MG ISOTOPES Measure isotope shifts compare static charge radii with radii from B(E2) (influence of 2 + deformation) from β-asymmetry detection need high precision / line shape analysis with bunched Mg ion beams (ISCOOL): improve sensitivity of optical detection several orders of magnitude ( 33 Mg in reach)

18 FUTURE MG ISOTOPES Measure isotope shifts compare static charge radii with radii from B(E2) (influence of 2 + deformation) from β-asymmetry detection need high precision / line shape analysis with bunched Mg ion beams (ISCOOL): improve sensitivity of optical detection ISOTOPES Extend studies to 74 with present detection method to 76 using bunched beams with ISCOOL other detection methods (RIS?) Ga ISOTOPES (Manchester proposal) Investigate onset of proton skin at neutron deficient side Investigate monopole migration beyond N=50, spin determinations, moment, radii

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20 Measurements on Mg ions: from A=24,25,26 (stable) to A=27,29,31,33 (beyond N=20 shell gap) Hyperfine Structure Yield ~ ions/puls 31 Mg in MgO β-nmr β-asymmetry(%) g = (3) P 3/2 F=1 F=2 S 1/2 F=0 Splitting ~ g(i+1/2) F=1 Unambiguous determination of 31 Mg spin I = ½ and positive parity µ = (15) µ N pure 2p2h intruder state! Neyens et al., PRL 94, (2005)