recent developments in laser spectroscopy for ribsexample 2: halo nuclei: charge radii of be...

Wilfried Nörtershäuser

Recent Developments in Laser Spectroscopy

for RIBs

BECOLA @MSUTRIGA-LASER

@ Mainz

Frequency Comb

Forth Harmonic Generation

Outline Lecture 1

Isotope Shift and Hyperfine Structure – A brief introduction

Collinear Laser Spectroscopy – Basic Approach

Example 1: The „Island of Inversion“ – Spectroscopy of Mg

- Optical Detection

- Optical Pumping and -Asymmetry Detection

- -NMR

Example 2: Halo Nuclei: Charge Radii of Be Isotopes and a

Test of NR-QED Calculations

- Collinear / Anticollinear Approach

Motivation

Laser Spectroscopy

nuclear

spin

magnetic

dipole

moment

nuclear

charge

radius

spectroscopic

quadrupole

moment

Mass Spectrometry

nuclear

binding

energy

=

?

ground state

properties of

exotic nuclei

Isotope Shift and the Nuclear Mass Effect

H HHHH

Normal Mass

Shift (NMS)Specific Mass Shift (SMS)

Isotope 1

Isotope 2

H. C. Urey

1931

Nobelpreis

1934

D

H

Field Shift (Finite Nuclear Size Effect)

rE

s

p

Mean-square charge radius

Electronic Factor

( Wavefunction)Nuclear

Size

Field Shift (Finite Nuclear Size Effect)

rE

s

p

rE

s

p

Mean-square charge radius

Observable:

Change in mean-square

charge radius

Electronic Factor

( Wavefunction)Nuclear

Size

Mass Dependence of Mass and Field Shift

Hyperfine Structure and Moments

IS

Isotope A=

Hyperfine Structure and Moments

IS

Isotope A=

Spin IMagnetic moment μ

Quadrupole moment Qs

)()()(

)()(

)()()(

111

1212

1121183

2

JJIIFFC

BJJII

JJIICCA

CWF

JI

BA eI )(0

zzsVQeB

Types of On-Line Laser Spectroscopy

laser photon

(eV,

few 100 THz)

fluorescence detection

atomic ground state

atomic excited stateHFS

fluorescence photon

detect change of atomic property• polarized nuclei• charge exchange cross section• collisional ionization cross section• laser ionization cross section • …

laser photon

atomic ground state

atomic excited state

Hyperfine splitting (100 MHz)

different (sub-)state

fluorescence photon

population transfer

λ1

laser photon

λ2

second step laser photon

ion detection

atomic ground state

excited state Hyperfinesplitting

continuum

Recent Laser Spectroscopic Work on Ground

State Properties

Halos and Clustering (TRIUMF, ISOLDE, GANIL, ATLAS)

Z-Dependence of Radii

N=32 Shell Closure? (JYFL, ISOLDE)

Monopole Migration of SPE

due to Tensor Force (ISOLDE)

Sudden Appearance of

Deformation at N=60,

(JYFL)

Simple Structure in Complex Nuclei(ISOLDE)

Deformation in the

Z=82, N=126 Region

(ISOLDE: COMPLIS,

RILIS,CRIS)

N=Z, 74Rb

CKM-Unitarity

(TRIUMF)

Heavy Elements: Th-Isomer, Ra, Fr (Parity Violation, EDM),(ISOLDE: CRIS, Trip, TRIUMF)

Beyond Z=100 (SHIP)

not complete …

Island of Inversion (ISOLDE)

12

The Optical Doppler Effect

The lights of the cars

approaching you are

bluish1, while the lights

of the ones moving away

from you are red

1 Xe front-lights

The Principle Setup of Collinear

Spectrosocpy

Ion beam

Laser

beam

Deflector

Photo

multiplier

= (U,m)

1laserion

Doppler-Tuning:

1laserion

2

0ion

2eUMc

e

U

Collinear Doppler shift:

Anticollinear Doppler shift:

Resonance condition: 0ion

UU

ion

ion

21

1

/

c

Fluorescence

Detection

Region

High-

Voltage

UFDR

The Principle Setup of Collinear

Spectrosocpy

Ion beam

Laser

beam

Deflector

Photo

multiplierFluorescence

Detection

Region

High-

Voltage

UFDR

Frequency

Am

plit

ude

mE

meUE

2

a 21

2

a

0

0Doppler

2 mceU

E

c

aU

Voltage UFDR

Count rate

• universal

• fast

• sensitive

• high resolutionVoltage

Frequency

Data Taking in Collinear Laser Spectroscopy

Ion beam

Laser

beam

Deflector

Photo

multiplierFluorescence

Detection

Region

High-

Voltage

UFDR

aU

The Island of Inversion

Figures taken from M. Kowalska, Dissertation, Universität Mainz (2006)

Optical Detection: Even Isotopes

M.

Ko

wa

lska e

t a

l.,

PR

C 7

7, 0

34

307 (

20

08

)

24Mg

32Mg

3s 2S1/2

3p 2P1/2

280 nm

Optical Detection: Odd Isotopes

3s 2S1/2

3p 2P1/2

280 nm

F=2

F=3

F=2

F=3

25Mg

I = 5/2

I < 0

F=0

F=1

F=1

F=0

27Mg

I = 1/2

I < 0

29Mg

F=2

F=1

F=2

F=1

I = 3/2

I > 0

Optical Pumping

Optical pumping with + polarized light

-Asymmetry Detection

Nuclei have a preferred direction

for -particle emission with respect

to their spin axis (Parity Violation).

Polarization -Asymmetry

-Asymmetry

-Asymmetry Detection of 29Mg

3s 2S1/2

3p 2P3/2

F

3

210

2

1

I = 3/2

I > 0


3s 2S1/2

3p 2P3/2

F

1

2

0

1

I = 1/2 ??

I < 0


01 12 11 01 11 10

3p 2P1/2

3s 2S1/2

3p 2P3/2

D2 Line

+

D2 Line

-

D1 Line

+

D1 Line

-

Nuclear Spin : I = 1/2

Expected: I = 3/2

-Nuclear Magnetic Resonance in 31Mg

HFS 31Mg II, D2

NMR 31Mg,

MgO

RF (kHz)

(MHz)

in a cubic crystal

NImag BgE

h

EmagL

-1/2

1/2I = 1/2 Emag

RF

Pmax

L

.

pola

risation

B

hg

N

LI

M.

Ko

wa

lska e

t a

l.,

PR

C 7

7, 0

34

307 (

20

08

)


HFS 31Mg II, D2

NMR 31Mg,

MgO

RF (kHz)

(MHz)

Proportionality factor A/g are

known from stable isotopes

pf

sd

20

31Mg (N=19)

d3/2

Ip=1/2+

G. Neyens et al., PRL 94, 022501 (2005)


D. Yordanov et al., PRL 99, 212501 (2007)

20

33Mg (N=21)

I p = 3/2-

pf

d3/2

s1/2

d5/2

Keep in Mind

• Optical hyperfine structure measurements can reveal

magnetic moments (size and sign)!

• The magnetic moment is very sensitive to the

wavefunction composition of a nuclear state

• -Asymmetry detection after optical pumping is a

sensitve tool to detect atomic resonance transitions

• -NMR can provide accurate values of nuclear g-factors

• Measuring the nuclear g factor and the hyperfine

splitting provides a direct measurement of the nuclear

spin I

recent developments in laser spectroscopy for ribsexample 2: halo nuclei: charge radii of be...

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