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
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
-Asymmetry Detection of 29Mg
-Asymmetry Detection of 31Mg
3s 2S1/2
3p 2P3/2
F
1
2
0
1
I = 1/2 ??
I < 0
-Asymmetry Detection of 31Mg
-Asymmetry Detection of 31Mg
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
)
-Nuclear Magnetic Resonance in 31Mg
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)
-Nuclear Magnetic Resonance in 31Mg
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