1. -“OROCHI” project - Laser spectroscopy of radioactive atoms
International Workshop on Physics of Nuclei at Extremes, ‘10 1/26 Tokyo TECH
Laser spectroscopy of radioactive atoms
embedded in superfluid He,
and a planned nuclear structure study
on proton-rich Ag isotopes
-“OROCHI” project -
Tokyo Institute of Technology
Takeshi Furukawa

2. Contents ・What is “OROCHI” ? ・Present status of “OROCHI”
nuclear laser spectroscopy in superfluid helium
　　 for the measurement of rare isotopes
not with high precision ,
but with sensitive to detect photons
・Present status of “OROCHI”
off-line development
with Rb, Cs, Ag, and Au stable isotopes
・Future prospect of “OROCHI”
on-line experiment plan for proton-rich Ag isotopes
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

3. Measurement of Nuclear Spin and Moment
Introduction:
Measurement of Nuclear Spin and Moment
Nuclear structure
interaction between atomic spin mF and external magnetic field
hyperfine interactions
Laser spectroscopy
atomic sublevel structure I J e F
external magnetic field B
hyperfine structures
Zeeman splittings
interaction between nuclear moments and electrons
nuclear spins
one of the most important quantities
for nuclear structure investigation
ex) orbital angular momentum
of valence nucleons,
configuration mixing …..
electromagnetic moments
Nuclear spin/moment measurement
on unstable nuclei far from stability line : difficult
- low yield
- large contamination
- small polarization
However...
IWPNE 2010, /26 Tokyo TECH, T. Furukawa 3

4. New Laser Spectroscopy
from “DRAEMON” vol. 22, by FUJIKO, F. Fujio
to measure the nuclear spins & moments in exotic nuclei…
“laser spectroscopy for radioisotope atoms in superfluid helium (He II)”
“OROCHI ”
Optical Radioisotope-atom Observation in Condensed Helium as Ion-catcher
Laser
Ion beam
(radioisotope
beam)
Separator
(i.e. BigRIPS in RIKEN)
Accelerator
(i.e. SRC in RIKEN)
RI beam
target
LIF
He II
((((((
radiowave or
microwave
hyperfine structure
Zeeman structure
nuclear moment
nuclear spin
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

5. Advantage in He II ( We use He II to reduce the b.g. photons.
① blue-shifted
Atomic absorption spectra in He II
② broadened
133Cs atomic spectra in He II
Excited with expanding the surrounding He
He II
atom
in vacuum
Laser
Detector
wavelength: lLIF ≠ llaser
Suppress background count
Reduction:10-10～10-13
He II
emission
Intensity (arb.unit)
absorption
光波長 (nm)
Wavelength (nm)
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

6. Advantages of laser spectroscopy
Laser induced fluorescence (LIF) photon
Scattered laser photon
absorb & emit photons cyclically
→ detect much photons/atom
(typically ~ photons /sec)
→ good statistic !!
Laser
Contaminant atoms: do not absorb laser light
→ observe only objective atoms !!
RI beam
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

7. (((((( Double resonance spectroscopy
measurement of atomic sublevel structure
：Double resonance spectroscopy
ILIF
rf frequency
expected spectrum
In the case of Zeeman splitting in alkali atoms
2nd step: double resonance
1st step : optical pumping
atoms
m = -1/2
m = +1/2
S1/2
P1/2 σ+ X
D1 Line
m = +3/2
rf-resonance
m = -1/2
m = +1/2
S1/2
P1/2 σ+ X
D1 Line
m = +3/2
m = -1/2
m = +1/2
S1/2
P1/2 σ+ X
m = +3/2
laser
No level B
(((((( rf
[ILIF] ∝ 1 - Pz
Emission photons in optical pumping
decreased gradually
(Laser Induced Fluorescence, LIF)
IWPNE 2010, /26 Tokyo TECH, T. Furukawa 7

8. Experimental Setup with stable isotope: Rb, Cs, Ag, Au, ….
To confirm the feasibility of OROCHI
with stable isotope: Rb, Cs, Ag, Au, ….
IWPNE 2010, /26 Tokyo TECH, T. Furukawa 8

9. Optical pumping in He II
T. Furukawa et al., Phys. Rev. Lett. 96, (2006)
Produce the polarization in stable Rb, Cs in He II
Polarization ：~90 %(Cs)
~50 %(Rb)
Polarization switched
Linearly
polarized
Circularly
Polarization: increased
LIF intensity: decreased
(Laser induced fluorescence)
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

10. Spin preservation in He II
- spin relaxation time of 133Cs atoms in He II -
long relaxation time (Cs atomic spin)
T. Furukawa et al., Phys. Rev. Lett. 96, (2006)
In He II : atoms can be polarized easily
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

11. Nuclear spin & moment determination atomic sublevel structure
Zeeman
splittings
hyperfine
splitting
Zeeman resonance of Rb isotopes
Hyperfine resonance of 85Rb
I85Rb = 2.6(1)
→ 5/2
I87Rb = 1.55(5)
→ 3/2
This work (from AHeII)
evaluated (from Avacuum)
literature value (NMR)
mI85Rb (mN)
(7) mN
(1) mN mN
ΔnZmn = gF mB B / h
2.8(MHz)×B(Gauss) =
(2I+1)
Nuclear spin
T. Furukawa, Doctoral thesis, Osaka Univ. (2007)
IWPNE 2010, /26 Tokyo TECH, T. Furukawa
T. Furukawa, et.al., Proceedins on INPC07 (2008)

12. Hyperfine structure in He II
- Atomic hyperfine structure in He II -
T. Furukawa et al., to be submitted...
B’ (> B)
Pressurized by helium
HeII (GHz)
vacuum (GHz)
Hyperfine coupling constant A
HeII/vacuum ratio
133Cs Rb 85 87
(3)
(3)
(5)
(1)
(3)
(1) B
<B>
isotope：
　same atomic structure
→approximately same <B>
w/o hyperfine anomaly
(Bohr-Weisskopf effect)
In vacuum
density
radius
electron
cloud
nucleus
hyperfine anomaly
In He II
density
radius
Hyperfine anomaly
85D 87
This work (from AHeII)
0.330 (5) %
literature value %
difference
5.0 ± 1.4 %
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

13. Our achievement Off-line development with stable isotope
・Producing high polarization in alkali Cs, Rb atoms
・determine nuclear spin & moment : Cs, Rb isotopes
Can we apply this OROCHI to atoms other than alkali?
Recently…
applying OROCHI to noble metal Ag, Au atoms.
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

14. Optical pumping of Ag, Au atoms
107,109
I=1/2
F=0 mF
Ag, Au：
atomic level structure is same as alkalis. P 2
1/2 +1
F=1
Feasible to optical pumping. However….
(in free-space) -1
338.29nm
F=0
No strong laser source just suited to absorption line S 2
1/2
Absorption line : in UV region +1
F=1 -1
D1 excitation spectrum of Ag atoms in HeⅡ
Ag atom: peak ：～333.5nm
width： ～5nm
In the case of He II…
Broadened absorption spectra.
We can prepare the pumping laser.
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

15. Laser spectroscopy of Ag and Au
T. Furukawa, K.Fujikake et al., to be published...
Applying to noble metal Ag and Au atoms
Broadened absorption spectra in He II.
→ feasible to optical pumping of various atomic species
(less limitation in laser wavelength)
polarization： ～８０％(Ag), ～６０％(Au)
incomplete polarization is due to imperfect circular polarization of laser
Nuclear spin I=1/2
can be deduced clearly.
Ag atomic sublevel structure I J
) ΔEZMN
Preliminary
Zeeman splitting of stable 107,109Ag isotopes (both I =1/2 )
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

16. Our achievement Off-line development with stable isotope next step:
・Producing high polarization in alkali Cs, Rb atoms
・determine nuclear spin & moment : Cs, Rb isotopes
・applying to Ag and Au atoms : successful
Can we apply this OROCHI to atoms other than alkali?
next step:
On-line experiment
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

17. N. J. Stone, At. Nucl. Data Tab. 90, 75 (2005)
Future prospect
RI (total): 0.1 pps
Isomer ratio: 5 %
(from RIBF facility)
1 day measurement
simulation Z N
N＝８２
Z＝５０
N＝５０
Stable line
g.s. moment is unknown
g.s. moment is known
g.s. moment is zero
　(even-even nuclei)
Stable isotope
N. J. Stone, At. Nucl. Data Tab. 90, 75 (2005)
1st goal :exotic N=Z nucleus 94Ag
I, m of g.s. and isomer state (21+)
expected yield: < 1 pps
(with BigRIPS)
measurable
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

18. On-line experiment with Rb beam
- 1st trial -
All the devices were mounted
on RIKEN RIPS beam line !!
Oh, my god......
cryostat
But Rb beam has not accelerated
due to machine trouble…
laser
Rb beam
Rb beam
Cryostat
Photo-detection system
The result will be shown next time …
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

19. of exotic nuclei, particularly proton drip-line, N=Z nucleus 94Ag
Conclusion
“OROCHI ” Project
Optical Radioisotope-atom Observation in Condensed Helium as Ion-catcher
We developed the new laser spectroscopy method “OROCHI” for determining
nuclear spins and moments of exotic RI far from stability by using superfluid
helium (He II) as a stopper of RI beam and host matrix of laser spectroscopy.
Atomic spectra in He II (largely blue-shifted and broadened) enable us
to measure for the extremely low yield RI whose yield is less than 1 pps.
In our off-line development using stable Rb and Cs isotopes, we have
successfully demonstrated the determination of nuclear spins and moments
from the measured Zeeman and hyperfine splitting respectively.
We have also demonstrated the optical pumping and double resonance
of stable Ag and Au isotopes in recently.
Preparation of setups for online experiment is almost finished.
We hope This OROCHI will open the door to measure the nuclear spins and moments
of exotic nuclei, particularly proton drip-line, N=Z nucleus 94Ag
IWPNE 2010, /26 Tokyo TECH, T. Furukawa

20. OROCHI - Collaborator Spokesperson:
Takeshi Furukawa (Tokyo Institute of Techinology), Yukari Matsuo (RIKEN)
RIKEN：
　 H. Ueno, N. Aoi, A. Yoshimi, K. Yoneda, Y. Togano, M. Takechi, Y. Ichikawa, S. Nishimura, M, Nishimura,
T. Kobayashi, M. Wada, T. Sonoda, A. Takamine, T. Motobayashi, …
Tokyo institute of Technology:
K. Asahi, Y. Kondo
CYRIC, Tohoku Univ.:
　 A. Sasaki, T. Wakui, H. Oouchi, S. Izumi, T. Shinozuka
Osaka Univ.:
　 M. Kazato, T. Shimoda, A. Odahara
This project is supported by
- Grant-in-Aid for Scientific Research
by the Ministry of Education, Culture,
Sports, Science, and Technology, Japan.
Program for Global Center of Excellence
“Nano-science and Quantum Physics”
in Tokyo Institute of Technology
Tokyo Univ. of Agriculture and Tech.：
　 A. Hatakeyama
Meiji Univ.:
　 Y. Matsuura, H. Kato
CNS, Univ. Tokyo:
　 S. Kubono, Y. Oshiro

21. Thank you for your attention.
IWPNE 2010, /26 Tokyo TECH, T. Furukawa