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Laser spectroscopy of radioactive atomsembedded in superfluid He,
and a planned nuclear structure studyon proton-rich Ag isotopes
-“OROCHI” project -
Laser spectroscopy of radioactive atomsembedded in superfluid He,
and a planned nuclear structure studyon proton-rich Ag isotopes
-“OROCHI” project -
Takeshi FurukawaTokyo Institute of Technology
International Workshop on Physics of Nuclei at Extremes, ‘10 1/26 Tokyo TECH
ContentsContentsContentsContents・ What is “OROCHI” ? nuclear laser spectroscopy in superfluid helium for the measurement of rare isotopes not with high precision , but with sensitive to detect photons
・ What is “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
・ 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
・ Future prospect of “OROCHI” on-line experiment plan for proton-rich Ag isotopes
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
nuclear spins
Nuclear structure
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
one of the most important quantities for nuclear structure investigation ex) orbital angular momentum of valence nucleons, configuration mixing …..
Introduction: Measurement of Nuclear Spin and MomentIntroduction: Measurement of Nuclear Spin and Moment
electromagnetic moments
interaction between atomic spin mF and
external magnetic field
hyperfine interactions
Laser spectroscopy
atomic sublevel structure
IJ
e
IJ
F
external magnetic
field B
hyperfine structuresZeeman splittings
interaction between nuclear moments
and electronsNuclear spin/moment measurement on unstable nuclei far from stability line : difficult - low yield - large contamination - small polarization
However...
New Laser SpectroscopyNew Laser Spectroscopy
“laser spectroscopy for radioisotope atoms in superfluid helium (He II)”
to measure the nuclear spins & moments in exotic nuclei…
“OROCHI ”“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
((((((
radiowaveor
microwave
hyperfine structure Zeeman structure
nuclear momentnuclear spin
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
from “DRAEMON” vol. 22, by FUJIKO, F. Fujio
光波長 (nm)
Inte
nsit
y (
arb
.un
it)
133Cs atomic spectra in He II
① blue-shifted(
absorption
in vacuum
emission
Excited with expanding the surrounding He
He II
atom
Laser
Detector
wavelength: LIF≠laserSuppress background
countReduction:10-10 ~ 10-13
He II
Advantage in HeAdvantage in He IIIIAdvantage in HeAdvantage in He IIII
② broadened
Wavelength (nm)
We use He II
Atomic absorption spectra in He II
to reduce the b.g. photons.
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
Laser
RI beam
absorb & emit photons cyclically
→ detect much photons/atom(typically ~ 105-108 photons /sec)
→ good statistic !!
Contaminant atoms: do not absorb laser light
→ observe only objective atoms !!
Laser induced fluorescence (LIF) photon
Advantages of laser spectroscopyAdvantages of laser spectroscopy
Scattered laser photon
B
laser
atoms
m = -1/2 m = +1/2
S1/2
P1/2σ+
XD1 Lineσ+
m = +3/2
measurement of atomic sublevel structure : Double resonance spectroscopy
In the case of Zeeman splitting in alkali atoms
[ILIF] 1 - P∝ z
Emission photons in optical pumping
decreased gradually
(Laser Induced Fluorescence, LIF)
m = -1/2 m = +1/2
S1/2
P1/2σ+
X
σ+
m = +3/2
1st step : optical pumping2nd step: double resonance
m = -1/2 m = +1/2
S1/2
P1/2σ+
XD1 Lineσ+
m = +3/2
rf-resonance
((((((((((((rf
ILIF
rf frequency
expected spectrum
Double resonance Double resonance spectroscopyspectroscopy
Double resonance Double resonance spectroscopyspectroscopy
No level
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
Experimental SetupExperimental Setup
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
with stable isotope: Rb, Cs, Ag, Au, ….To confirm the feasibility of OROCHI
m = -1/2 m = +1/2
S1/2
P1/2σ +
Xσ +
m = +3/2
m = -1/2 m = +1/2
S1/2
P1/2σ +
Xσ +
m = -1/2 m = +1/2
S1/2
P1/2σ +
Xσ +
m = +3/2
Optical pumping in He IIOptical pumping in He II
Polarization : ~90 %(Cs) ~50 %(Rb)
5 ms
直線偏光
円偏光
Time (ms)
ph
oto
n c
ou
nts
5 ms
偏光切替Polarization switched
Linearly polarized
Circularly polarized
T. Furukawa et al., Phys. Rev. Lett. 96, 095301 (2006)
Produce the polarization in stable Rb, Cs in He II
Polarization: increased
LIF intensity: decreased
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
(Laser induced fluorescence)
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
Spin preservation in He IISpin preservation in He II
In He II : atoms can be polarized easily
long relaxation time (Cs atomic spin)
- spin relaxation time of 133Cs atoms in He II -
T. Furukawa et al., Phys. Rev. Lett. 96, 095301 (2006)
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
atomic sublevel structure
Zeemansplittings
85Rb
Magnetic field B = 4.0(1) Gauss
1.8203(2) MHz
87Rb 2.7357(6) MHz
Ph
oto
n C
ou
nts
(C
ou
nts
/ b
in)
Zeeman resonance of Rb isotopes
ΔZmn = gF mB B / h
2.8(MHz)×B(Gauss)= (2I+1)
Nuclear spin
Nuclear spin & moment determinationNuclear spin & moment determination
T. Furukawa, Doctoral thesis, Osaka Univ. (2007)
T. Furukawa, et.al., Proceedins on INPC07 (2008)
I85Rb = 2.6(1) → 5/2
I87Rb = 1.55(5) → 3/2
hyperfinesplitting
This work (from AHeII)
evaluated (from Avacuum)
literature value (NMR)
I85Rb (N)
1.357 83 (7) N
1.358 071(1) N
1.353 351 5 N
Hyperfine resonance of 85Rb
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
In He IIdensity
radius
<B> isotope : same atomic structure
→approximately same <B> w/o hyperfine anomaly (Bohr-Weisskopf effect)
Hyperfine anomaly 8587
This work (from AHeII) 0.330 (5) %
literature value 0.3474 %
difference 5.0 ± 1.4 %
- Atomic hyperfine structure in He II - T. Furukawa et al., to be submitted...
HeII (GHz) vacuum (GHz)
Hyperfine coupling constant A HeII/vacuum ratio
133Cs
Rb85
87
2.31283(3) 2.29815794
1.01700(3)
3.43514(5) 3.41734131
1.01191092
1.00638(1)
1.00503(3)
1.00521(1)
BB’ (> B)
Pressurized by helium
In vacuumdensity
radius
electron cloud
nucleus
RbRbI
RbRbI
Rb
Rb
I
I
A
A8787
8585
87
85
/
/
87851 hyperfine anomaly
Hyperfine structure in He IIHyperfine structure in He II
Our achievementOur achievementOur achievementOur achievement
Off-line development with stable isotope
・ determine nuclear spin & moment : Cs, Rb isotopes
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
・ Producing high polarization in alkali Cs, Rb atoms
Can we apply this OROCHI to atoms other than alkali?
Recently… applying OROCHI to noble metal Ag, Au atoms.
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
Ag,107,109 I=1/2
(in free-space)338.29nm
F=1
mFF=0
+1
-1
0
0
F=1
F=0
+1
-1
0
0
S2 1/2
P2 1/2
atomic level structure is same as alkalis.
Ag, Au :
Feasible to optical pumping. However….
D1 excitation spectrum of Ag atoms in HeⅡ
Ag atom: peak :~333.5nm
width : ~5nm
Optical pumping of Ag, Au atomsOptical pumping of Ag, Au atoms
No strong laser source just suited to absorption lineAbsorption line : in UV
region
In the case of He II…Broadened absorption
spectra.
We can prepare the pumping laser.
Laser spectroscopy of Ag and AuLaser spectroscopy of Ag and AuT. Furukawa, K.Fujikake et al., to be published...
polarization : ~80% (Ag), ~60% (Au) incomplete polarization is due to imperfect circular polarization of laser
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)
Nuclear spin I=1/2 can be deduced clearly.
Ag atomic sublevel structure
IJ
) ΔEZMN
Preliminary
Zeeman splitting of stable 107,109Ag isotopes (both I =1/2 )
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
Our achievementOur achievementOur achievementOur achievement
Off-line development with stable isotope
・ determine nuclear spin & moment : Cs, Rb isotopes
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
・ Producing high polarization in alkali Cs, Rb atoms
next step: On-line experiment
・ applying to Ag and Au atoms : successfulCan we apply this OROCHI to atoms other than alkali?
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)
Future prospectFuture prospect
measurable
1st goal :exotic N=Z nucleus 94Ag I, of g.s. and isomer state (21+) expected yield: < 1 pps (with BigRIPS)
RI (total): 0.1 ppsIsomer ratio: 5 % (from RIBF facility)1 day measurement
simulationsimulation
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
On-line experiment with Rb beam- 1st trial -
On-line experiment with Rb beam- 1st trial -
Rb beam
laser
cryostat
All the devices were mounted on RIKEN RIPS beam line !!All the devices were mounted on RIKEN RIPS beam line !!
Oh, my god......
But Rb beam has not accelerated due to machine trouble…But Rb beam has not accelerated due to machine trouble…
Rb beam
Cryostat
Photo-detection system
The result will be shown next time …The result will be shown next time …
ConclusionConclusion
“OROCHI ” Project“OROCHI ” ProjectOptical 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.
We hope This OROCHI will open the door to measure the nuclear spins and momentsof exotic nuclei, particularly proton drip-line, N=Z nucleus 94Ag
- Preparation of setups for online experiment is almost finished.
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa
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, …
Osaka Univ.: M. Kazato, T. Shimoda, A. Odahara
CYRIC, Tohoku Univ.: A. Sasaki, T. Wakui, H. Oouchi, S. Izumi, T. Shinozuka
Meiji Univ.: Y. Matsuura, H. Kato
OROCHI - CollaboratorOROCHI - Collaborator
Tokyo Univ. of Agriculture and Tech. : A. Hatakeyama
Tokyo institute of Technology: K. Asahi, Y. Kondo
Spokesperson: Takeshi Furukawa (Tokyo Institute of Techinology), Yukari Matsuo (RIKEN)
Email: [email protected]
CNS, Univ. Tokyo: S. Kubono, Y. Oshiro
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
Thank you for your attention.Thank you for your attention.
IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa