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

Univ. Mainz: M. Kowalska, R. NeugartK.U.Leuven: D. Borremans, S. Gheysen, P. Himpe, P. Lievens, S. Mallion,

G. Neyens, D.Yordanov, N. VermeulenCERN: K. Blaum

Spokesperson: Gerda NeyensContact Person: Magda Kowalska

INTC-P-183

Motivation

8 2010111213

Earlier and ongoing work:

At ISOLDE: - ground state properties of the Na isotopes

M. Keim et al., PhD Thesis, Univ. MainzENAM ’98 EJP A8 (2002) 31and in preparation

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 quite essential to study an isotope chain systematically from the normal-dominant to the intruder-dominant nuclei to examine the N =20 shell gap. In particular, nuclei at the boundary will give much information ! “

For 30Na (N=18) the 2p2h configurations are mixed in the ground state by 40%,enlarging the quadrupole moment fromthe sd-shell value.

At N =19 and 20 : a very good agreement for the MCSM both ground states aredominated by the 2p2h configurations.

Extra neutron correlations in the intruder configurations induce the change in deformation

Data on Na-isotopes: M. Keim et al., ENAM ’98 and EJP A8 (2002) 31

MSCM calculationsIncluding mixing between normal and intruder configurations

Motivation

8 2010111213

Earlier and ongoing work:

At ISOLDE: - ground state properties of the Na isotopes

- ground state properties of the Ne isotopesW. Geithner et al. PhD thesis, Univ. Mainz

papers in preparation

A. Bhagwat and Y. K. GambhirPHYSICAL REVIEW C 68, 044301 (2003)

Recently observed charge radius anomaly in neon isotopes

Relativistic mean field (RMF) calculations

isotopic shifts (a) charge radii (b) Data on Ne-isotopes: W. Geithner, PhD thesis,

papers in preparation

19-23Ne have strong prolate deformation (neutron deficient nuclei)

The shape transition is observed between 23Ne and 24Ne.

The higher neon isotopes have relatively milder deformations !

It turns out that except for 20-22,28Ne, all the neon isotopes have very small or zero neutronpairing energies. This reflects that the deformation effects are largely due to the protons.

Motivation

8 2010111213

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

S. Teughels et al., PhD thesis K.U. Leuven D. Borremans et al., PLB 537 (2002) 45D. Borremans et al., PRC 66 (2002) 054601

P. Himpe et al., PhD thesis KU Leuven, in preparationP. Himpe et al., in preparation

Systematic study of moments of Al isotopes

D. Borremans et al., PLB 537 (2002) 45

P. Himpe et al., in preparation

32Al : agreement with sd-shell model

34Al: under investigation

+ study of Q-moments !

MCSM

33Al: in between sd-shell model and MSCMI. Utsuno et al., PRC 64 (2001) 011301(R)

31Al : agreement with sd-shell model

Motivation

8 2010111213

Earlier and ongoing work:

At ISOLDE (experiments finished): - ground state properties of the Na isotopes

At GANIL (experiments ongoing):- study of neutron rich Al-isotopes

- ground state properties of the Ne isotopes

Started at GANIL CONTINUE AT ISOLDE

- GROUND STATE PROPERTIES OF Mg isotopes

Motivations

8 2010111213

(3) Deformation changes between N=8 and N=20

(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

(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

Experimental methods Collinear Laser Spectroscopy (COLLAPS) set-up

Fine structurenlJ

3s1/2

~10GHz3p1/2

3p3/2

382 MHz5/23/2

Hyperfine structure|I-J| F I+J

5/23/2

44 MHz

I=2 (8Li)

680 nm for Li280 nm for Mg+

(frequency doubling)

Electron orbitsnl

~ 106 GHz

3s

3p

Measure hyperfine structure * optical detection of fluorescence light

(need 106 ions/s) * detection of the -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

Experimental methods Optical pumping + -NMR

N1

N2Optical pumping

-asymmetry~ N1/N2

-detection:-hyperfine spectra -NMR spectra

3.5 4.0 4.5 5.0 5.50.35

0.36

0.37

0.38

0.39

0.40

D1lijn

N1/N

2

~ Laser frequency

F1

F2

+

D1-line, 8Li

-

Asy

mm

etry

10 15 20 25

-0.080

-0.075

-0.070

-0.065

-0.060

-0.055

-0.050

-0.045

-0.040

y0 -0.060(1)xc 17.3(4)w 1.4(5)A 0.012(3)

Y Ax

is Tit

le

X Axis Title10 15 20 25

Q[kHz]

-0.07

-0.06

-0.05

-0.04

11Li(Zn) Q

5.340 5.342 5.344 5.346 5.348 5.350 5.3520.030

0.035

0.040

0.045

0.050

0.055

0.060

0.065y0 0.041(1)xc 5.3461(3)w 0.0010(3)A 0.016(6)

Y Ax

is Ti

tle

X Axis Title

11Li(Si) g

5342 5346 5350rf [kHz]-

asym

met

ry

0.04

0.05

0.06

Feasibility: polarizing Mg ions

D2-line (29Mg+) part of D2-line (31Mg+)Measured asymmetry for 31Mg(MgO)

Need for intense UV-light !

excitation from the ionic Mg+ ground state to one of the first excited p-states, 3s 2S1/2 3p 2P1/2 or 3p 2P3/2

laser = 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).

(1) neutron rich isotopes: UC2-target 29Mg - 31Mg - 33Mg beams

OBSERVED RATES 6.106 - 3.105 - 8.103 ions/pulse

BEAM TIME REQUEST

We request 35 shifts.We can report on the project status after 1

year.

-NMR techniques applicable on all isotopes (g-factor, Q-moments) -asymmetry measurement of hyperfine structure

(spins and sign FOR ODD ISOTOPES)

optical detection of hyperfine structure applicable for radioactive 27Mg, 29Mg (spins, sign of , charge radii)

radioactive 28Mg, 30Mg (charge radii) stable 24Mg, 25Mg, 26Mg (spins, , charge radii)

(2) neutron deficient isotopes: SiC target 21Mg, 23Mg yields to be tested !

23Mg: g and Q measured can serve as calibration

Beam time request

Neutron rich isotopes:

(1) hyperfine spectra of polarized 29Mg, 31Mg, 33Mg beams 5 shifts

(2) -NMR in cubic MgO crystal (g-factor) 29Mg,31Mg,33Mg beams 9 shifts

(3) -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) -NMR/LMR 8 shifts

(b)

I=5/2

I=3/2

I=7/2

(a)

(c)

31Mg in Mg single crystalLevel Mixing (=15º)

Conclusions:

(1)a long-lived I=7/2 in 31Mg

(2) ratio of /Q

- Position Q/ - Amplitude orientation- Width angle

LMR : Level Mixing Resonance

NIM A340 (1994) 555 G. Neyens et al.PRC 59 (1999) 1935 N. Coulier et al.PRC 63 (2001) 054605 N. Coulier et al.

Polarization in the LMR

-Number of resonances spin I- + distance between resonances