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Nuclear moments and charge radii of Mg isotopes from N=8 up to (and beyond) N=20

Nuclear moments and charge radii of Mg isotopes from N=8 up to (and beyond) N=20. Spokesperson: Gerda Neyens Contact Person: Magda Kowalska. Univ. Mainz: M. Kowalska, R. Neugart K.U.Leuven: D. Borremans, S. Gheysen, P. Himpe, P. Lievens, S. Mallion, G. Neyens, D.Yordanov, N. Vermeulen

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Nuclear moments and charge radii of Mg isotopes from N=8 up to (and beyond) N=20

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  1. Nuclear moments and charge radii of Mg isotopes from N=8 up to (and beyond) N=20 Spokesperson: Gerda Neyens Contact Person: Magda Kowalska Univ. Mainz: M. Kowalska, R. Neugart K.U.Leuven: D. Borremans, S. Gheysen, P. Himpe, P. Lievens, S. Mallion, G. Neyens, D.Yordanov, N. Vermeulen CERN: K. Blaum INTC-P-183

  2. Motivation 13 12 Earlier and ongoing work: At ISOLDE: - ground state properties of the Na isotopes 11 10 20 8 M. Keim et al., PhD Thesis, Univ. Mainz ENAM ’98 EJP A8 (2002) 31 and in preparation

  3. MSCM calculations Including mixing between normal and intruder configurations Data on Na-isotopes: M. Keim et al., ENAM ’98 and EJP A8 (2002) 31 Y. Utsuno, T. Otsuka et al. Progress of Theoretical Physics Supplement No. 146 (2002)488 MSCM calculations for Na isotopes Extract from the paper: “It is quiteessential to study an isotope chain systematically from the normal-dominant to theintruder-dominant nuclei to examine the N =20 shell gap. In particular, nuclei at theboundary will give much information ! “ For 30Na (N=18) the 2p2h configurationsare mixed in the ground state by 40%, enlarging the quadrupole moment from the sd-shell value. At N =19 and 20 : a very good agreement for the MCSM  both ground states are dominated by the 2p2h configurations. Extra neutron correlations in the intruder configurations induce the change in deformation

  4. Motivation 13 12 11 10 20 8 - ground state properties of the Ne isotopes W. Geithner et al. PhD thesis, Univ. Mainz papers in preparation Earlier and ongoing work: At ISOLDE: - ground state properties of the Na isotopes

  5. isotopic shifts (a) charge radii(b) Data on Ne-isotopes: W. Geithner, PhD thesis, papers in preparation A. Bhagwat and Y. K. Gambhir PHYSICAL REVIEW C 68, 044301 (2003) Recently observed charge radius anomaly in neon isotopes Relativistic mean field (RMF) calculations 19-23Ne have strongprolate deformation (neutron deficient nuclei) The shape transition is observed between23Ne and 24Ne. The higher neon isotopes have relativelymilder deformations ! It turns out that except for20-22,28Ne, all the neon isotopes have very small or zero neutron pairing energies. This reflects that the deformation effectsare largely due to the protons.

  6. Motivation 13 12 11 10 20 8 At GANIL (experiments ongoing): - study of neutron rich Al-isotopes S. Teughels et al., PhD thesis K.U. Leuven D. Borremans et al., PLB 537 (2002) 45 D. Borremans et al., PRC 66 (2002) 054601 P. Himpe et al., PhD thesis KU Leuven, in preparation P. Himpe et al., in preparation Earlier and ongoing work: At ISOLDE (experiments finished): - ground state properties of the Na isotopes - ground state properties of the Ne isotopes

  7. Systematic study of moments of Al isotopes D. Borremans et al., PLB 537 (2002) 45 P. Himpe et al., in preparation MCSM 31Al : agreement with sd-shell model 33Al: in between sd-shell model and MSCM I. Utsuno et al., PRC 64 (2001) 011301(R) 32Al : agreement with sd-shell model 34Al: under investigation + study of Q-moments !

  8. Motivation 13 12 11 10 20 8 Earlier and ongoing work: At ISOLDE (experiments finished): - ground state properties of the Na isotopes - ground state properties of the Ne isotopes At GANIL (experiments ongoing): - study of neutron rich Al-isotopes Started at GANIL  CONTINUE AT ISOLDE - GROUND STATE PROPERTIES OF Mg isotopes

  9. Motivations 13 12 • (1) Nuclear structure approaching the proton drip line / mirror nuclei. • - determine ground state spin/parity of 21Mg • - test of isospin symmetry in sd-shell: •  magnetic moments of T=3/2 mirror pair 21Mg – 21F 11 10 • (2) Nuclear structure around N=20: borders of the ‘Island of Inversion’ • - determine spin/parity of 31,33Mg ground states (and isomeric states) • - g-factor and Q-moments • single particle structure, admixture with 2p-2h intruder states • - shape coexistence in the N=20 region 20 8 • (3) Deformation changes between N=8 and N=20

  10. Experimental methods Collinear Laser Spectroscopy (COLLAPS) set-up ~10GHz 3p3/2 I=2 (8Li) 5/2 44 MHz 3p 3/2 3p1/2 680 nm for Li 280 nm for Mg+ (frequency doubling) ~ 106 GHz 5/2 382 MHz 3/2 3s 3s1/2 Hyperfine structure |I-J|  F  I+J Electron orbits nl Fine structure nlJ Measure hyperfine structure * optical detection of fluorescence light (need 106 ions/s) * detection of the b-asymmetry of optically polarized ions (polarized laser light) (need 103 ions/s) Hyperfine structure gives first information on - magnetic moment and sign ! - nuclear spin - mean square charge radius

  11. Experimental methods Optical pumping + b-NMR D1-line, 8Li N1 m b-asymmetry ~ N1/N2 F2 F1 s+ s+ N2 Optical pumping N1/N2 b-detection: b-hyperfine spectra b-NMR spectra 11Li(Si)  g 0.06 11Li(Zn)  Q -0.04 0.05 -0.05 b-asymmetry • b-Asymmetry -0.06 0.04 -0.07 ~ Laser frequency 25 10 15 20 nrf [kHz] 5342 5350 5346 DQ[kHz]

  12. D2-line (29Mg+) part of D2-line (31Mg+) Measured asymmetry for 31Mg(MgO) Feasibility: polarizing Mg ions Need for intense UV-light ! excitation from the ionic Mg+ground state to one of the first excited p-states, 3s2S1/2 3p2P1/2 or 3p2P3/2 laser l = 280 nm requires a frequency doubling of CW dye laser radiation. Major investment (funds and manpower)  installed an external ring cavity for efficient frequency doubling of the available dye laser radiation at 560 nm.  gained factor 10 in laser power compared to doubling with internal cavity (test run 10-11 october 2003).

  13. BEAM TIME REQUEST (1) neutron rich isotopes: UC2-target 29Mg - 31Mg - 33Mg beams OBSERVED RATES 6.106 - 3.105 - 8.103 ions/pulse  b-NMR techniques applicable on all isotopes (g-factor, Q-moments)  b-asymmetry measurement of hyperfine structure (spins and sign m FOR ODD ISOTOPES)  optical detection of hyperfine structure applicable for radioactive 27Mg, 29Mg (spins, sign of m, charge radii) radioactive 28Mg, 30Mg (charge radii) stable 24Mg, 25Mg,26Mg (spins, m, charge radii) (2) neutron deficient isotopes: SiC target 21Mg, 23Mg yields to be tested ! 23Mg: g and Q measured  can serve as calibration We request 35 shifts. We can report on the project status after 1 year.

  14. Beam time request Neutron rich isotopes: (1) hyperfine spectra of polarized 29Mg, 31Mg, 33Mg beams 5 shifts (2) b-NMR in cubic MgO crystal (g-factor) 29Mg,31Mg,33Mg beams 9 shifts (3) b-NMR/LMR in MgF2 crystal (EFG for Q-moment) 29Mg,31Mg,33Mg beams 15 shifts (4) reference measurement of larmor frequency of 8Li 2 shifts (5) isotope shifts of even isotopes (optical detection) 3 shifts Neutron deficient isotopes: (1) hyperfine spectra of polarized 21Mg, 23Mg 4 shifts (2) b-NMR/LMR 8 shifts

  15. (a) I=3/2 (b) I=5/2 (c) I=7/2 31Mg in Mg single crystal Level Mixing (b=15º) • Conclusions: • a long-lived I=7/2 in 31Mg • ratio of m/Q

  16. Polarization in the LMR LMR : Level Mixing Resonance NIM A340 (1994) 555 G. Neyens et al. PRC 59 (1999) 1935 N. Coulier et al. PRC 63 (2001) 054605N. Coulier et al. • - Position Q/ • Amplitude orientation • Width angle  • Number of resonancesspin I • - + distance between resonances

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