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International Nuclear Physics Conference 2007 - Jun. 4 -. Hyperfine structure of 85,87 Rb and 133 Cs atoms in superfluid helium. Development of new laser spectroscopy project using superfluid helium stopper. Takeshi Furukawa. Nishina-Center, RIKEN. Collaborator. - PowerPoint PPT Presentation
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Takeshi FurukawaTakeshi Furukawa
International Nuclear Physics Conference 2007 - Jun. 4 -
Hyperfine structure of 85,87Rb and 133Cs atoms in superfluid heliumHyperfine structure of 85,87Rb and 133Cs atoms in superfluid helium
Nishina-Center, RIKENNishina-Center, RIKEN
Development of new laser spectroscopy projectusing superfluid helium stopper
CollaboratorY. Matsuo1, A. Hatakeyama2, T. Ito3, K. Fujikake3
T. Kobayashi1, and T. Shimoda4
1Nishina-Center, RIKEN,2Dept. Appl. Phys., Tokyo Univ. of Agr. Tech.,
3Dept. Phys., Meiji Univ.4Dept. Phys., Osaka Univ.
1) Our New laser spectroscopy project
Contents Contents
2) Measurement data in the development
3) Summary and future prospect
Laser spectroscopy & optical detection・ Double resonance method in He II
Optical pumping in He II(
・ Long atomic spin relaxation time in He II・ hyperfine resonance spectrum of 85,87Rb and 133Cs in He II
・ determination of nuclear magnetic dipole moment・ hyperfine anomaly in He II
International Nuclear Physics Conference 2007 - Jun. 4 -
Optical RI-atom Observation in Condensed Helium
OROCHI projectOROCHI project(tentative)
RI beam
Laser
RI atomHe II liquid
wavelength separator & photon detector
effective stopping & trapping of RI atoms
using superfluid helium as a stopper & trap
Development : laser spectroscopy for short-lived RI atoms
Overview of Our MethodOverview of Our Method
purposeSystematical measurement ofunknown hyperfine structures
in exotic RI atoms
Laser induced fluorescence (LIF)
from “DRAEMON” vol. 22, by FUJIKO, F. Fujio
International Nuclear Physics Conference 2007 - Jun. 4 -
Laser
He II
RI beam
absorb & emit photons cyclically
→ detect much photons/atom(typically ~ 105-108 photons /sec)
→ good statistic !!
Contaminated atoms: no absorbing laser light
→ observe only objective atoms !!
absorption spectra in He II : largely broadened & blue-shifted.
wavelength : λatoms ≠λlaser
suppress the detection of scattered laser light
Nuclear Laser SpectroscopyNuclear Laser Spectroscopy
feasible to achieve optical pumping of various atomic species
i.e.) In, Tl, ….
International Nuclear Physics Conference 2007 - Jun. 4 -
Laser induced fluorescence (LIF) photon
Scattered laser photon
Double Resonance MethodDouble Resonance Method
LIF Intensity ∝ 1 - Pz
Polarized atoms : Can not absorb circularly polarized laser light.
LIF
inte
nsi
ty
microwave frequency
expected spectrum
Purpose: measure the hyperfine structure of RI atom
International Nuclear Physics Conference 2007 - Jun. 4 -
T. Furukawa et al., Phys. Rev. Lett. 96, 095301 (2006)
long spin relaxation time in He II has been measured.
133Cs atoms in He II
feasible to achieve optical pumping
Spin relaxation in He IISpin relaxation in He II
extremely longer than optical pumping time
International Nuclear Physics Conference 2007 - Jun. 4 -
To polarize the atoms : spin relaxation time is important
CsI
Cs
Cs
Experimental SetupExperimental SetupInternational Nuclear Physics Conference 2007 - Jun. 4 -
Measurement of the hyperfine splitting in Cs, Rb atoms
Double resonance peak in He IIDouble resonance peak in He II
ν133Cs= 9.2580915 (4) GHz
A133Cs = 2.312 76(2) GHz( Preliminary )
measured spectrum using double resonance method
ν85Rb= 3.05802 (10) GHz
A85Rb = 1.01702(2) GHz( Preliminary )
ν87Rb= 6.87652 (10) GHz
A87Rb = 3.43517(4) GHz( Preliminary )
Hyperfine resonance measurement : stable 133Cs, 85,87Rb
International Nuclear Physics Conference 2007 - Jun. 4 -
HH’ (> H)
Pressurized by helium
Calcuration from hyperfine coupling constant
85Rb () 8587
This work (from AHeII) 1.357 84 (1) 0.331 7 (7) %
literature value 1.353 351 5 0.348 7 (3)%
difference 0.331 7 (7)
%4.8 (2) %
Hyperfine Structure in He IIHyperfine Structure in He II
In He II
electron
nuclei
Hyperfine coupling constant A
He II (GHz) Vacuum (GHz) A/A (%)
133Cs 2.31276 (2) 2.2981579 0.635 (1)
Rb85 1.01702 (2) 1.0119109 0.505 (2)87 3.43517 (4) 3.4173413 0.522 (1)
Enable to obtain the nuclear information efficiently!!
International Nuclear Physics Conference 2007 - Jun. 4 -
for RI Beam Experimentfor RI Beam Experimentto confirm the feasibility of our project
Laser Induced Fluorescence
( LIF )Lens
Optical filter
Lens
Wavelength plate
Wavelength plate
measure the LIF photons from RI atoms
estimated lower limit of the beam intensity to measure : only 10 cps
International Nuclear Physics Conference 2007 - Jun. 4 -
ConclusionConclusion
・ deduce nuclear moment with 1% accuracy・ deduce hyperfine anomaly with 5% accuracy
133Cs, 85,87Rb hyperfine splitting in He II
* Nuclear spin can be also determined with rf-resonance
measure the hyperfine structure of exotic RI atoms
Optical RI-atom Observation in Condensed Helium
OROCHI projectOROCHI project(tentative)
We are now developing successfully…
~Next plan~+ RI beam experiment (plan: in next year)+ Optical pumping of various elements (In, Tl, Ca, ….)
International Nuclear Physics Conference 2007 - Jun. 4 -
Goal : measurement of In, Tl isotopes
Additional OHPAdditional OHP
International Nuclear Physics Conference 2007 - Jun. 4 -
ふろく
85Rb
87Rb高さの比 = 6636/22370 = 0.297同位体比= 27.85/72.15 = 0.386 → rfパワーが違うため?
周波数比 = 1815/2720 ≒ 2/3理論比 = gF=3/gF=2 ≒ 2/3 →未知の核種の核スピン同定が可能!
Zeeman sublevels of 85,87Rb
Pressure effect in HeII
H
< < 1% increase1% increase
A=<H>/I ・ JDifference of <H> in He II H’ (> H)
Pressurized by helium
Compressed atom by surrounding helium
Affect to the orbital of valence eveltrons
HeII (GHz) vacuum (GHz)
Hyperfine coupling constant HeII/vacuum ratio
133Cs
Rb85
87
2.31276(2) 2.29815794
1.01702(2)
3.43517(4) 3.41734131
1.01191092
1.00635(1)
1.00505(2)
1.00522(1)
ΔCs > ΔRb
VCs > VRb
Determination of 85Rb moment
NRb
RbRb
IRbRbRb
IRb
I A
AgIIg )1(35784.1
87
858785858585
Deduce 85Rb moment with 87Rb moment as reference
))2(751818.2( 8787N
RbRbI Ig
literature value : NRb
I )8(3533515.185
・ possible to determine the moment with 1% accuracy
・ difference ( ~ 0.3%) ← caused by hyperfine anomaly
Effect of the distribution of nuclear magnetization
electron
nuclei
Use A value in vacuum: NRb
I )1(357782.185
Hyperfine anomaly in He II
)1(
1878587
858785858585
Rb
RbRb
IRbRbRb
IRb
I A
AgIIg
Considering hyperfine anomaly…
)%7(3317.08785 HeII
In HeII
In vacuum
%3487.08785 vacuum
)~5% difference
hyperfine anomaly
Due to the deformed electron distribution by the pressure of surrounding He ??
In vacuum In HeII
Hyperfine Interaction
Hyperfine InteractionW(F, mF)= A ・ K/2 + B ・ {3K(K+1)/4 –I(I+1)J(J+1)}/{2(2I-1)(2J-1)IJ}
[K=F(F+1)-I(I+1)-J(J+1)]
Measure the constant A, B of isotope mX and nX
A=<B>/IJ B=eQ<V>I:nuclear spin, J:electronic angular momentum,: nuclear magnetic dipole moment,eQ: nuclear electric quadrupole moment,<B>:magnetic field produced by the electrons<V>:electric field gradient produced by the electros
mXnX
=AmX ImXAnX InX
eQmX
eQnX
BmXBnX
=
absorption spectrum in He II① Blue-Shifted② Broadened(
Deform
absorption
emission
Energ
y
Bubble model
absorption emissio
n
Bubble radiusEnergy levels in the ground state and excited state
as a function of bubble radius.
Deform
Effect of surrounding He atoms
Excitation Spectrum in He IIExcitation Spectrum in He II
Wavelength (nm)
absorption spectrum in He II(
Inte
nsity
(arb
.uni
t)
absorption : peak ~876 nm, width ~15 nm
emission : peak ~892 nm, width ~3 nm
133Cs atomic spectra in He II
(in vacuum: 894.347nm)
absorption≠emission
① Blue-Shifted② Broadened(
by the pressure of surrounding He atoms
Optical Merit in He IIOptical Merit in He II
Laser
Detector
wavelength: λLIF≠λlaser
suppress the detection of scattered laser light
In vacuum In He II
Need many laser lights!
Excitation with only single laser light
Feasible to acheve optical pumping
absorption spectrum in He II(① Blue-Shifted② Broadened(
Optical Pumping
Optical pumping method
LIF Intensity ∝ 1 - Pz
B
laser
atom
( in the case of alkali atoms J=1/2 )
After the polarizing of atoms…
Decrease LIF intensity(Laser Induced Fluorescence, LIF)m = -1/2 m = +1/2
S1/2
P1/2σ+
XD1 Lineσ+
m = -1/2 m = +1/2
X
S1/2
P1/2
D1 Line
σ+ σ+
Optical Pumping of Metastable Mg atoms
21Mg atomic energy diagram Observable resonance line (Assume I = 5/2)
3s3p 3P2 F=9/2 ⇔ F=7/2
[h.f.s = (9/2)A + (27/40)B]
F=7/2 ⇔ F=5/2 [h.f.s = (7/2)A + (7/40) B]
( 3s3p 3P1 F=7/2 ⇔ F=5/2 )
Optical Pumping of Al atoms
27Al の原子準位図3s23p 2P1/2,3/2 ⇔ 3s24s 2S1/2 transition
・ 3s23p 2P1/2,3/2,mF>+3 の準位→ 円偏光 (σ+) を吸収不可能
特定の磁気状態に原子状態が集中 = 偏極生成可能!!350 355 360 365 370
Wavelength nm( )
LIF in
tens
ity
a.u.
()
問題点:基底状態 (3s23p 2P1/2,3/2) の偏極緩和時間2P3/2 :電子軌道が非対称→緩和しやすい2P1/2 :電子軌道が球対称→緩和しにくい
→2P1/2 では偏極生成可能?
Relaxation in the Dark Method
→“Relaxation in the dark” method
detect the photons only from the “spin relaxed” atoms
Measure the relaxation time
Timing chart
Spin relaxation time in He II
偏極ゼロ時の LIF 強度
Dark period 後の LIF 強度
Measured LIF intensity
Demerits in Optical Detection
Demerits in Optical Detection
Problems in laser spectroscopic study of RI atoms
・ stopping & Trapping efficiency
In He II ・・・
・ possible elements
B.G. count of stray light
Using the characteristic spectrum of atoms in He II
→Subtract the problems
Interaction with surrounding He
Introduced to condenced helium → observe all of the stopped atoms
high trapping efficiency
Stopped & trappedRI Beam
Laser
Scientific MotivationScientific Motivation
Unstable nuclei near the drip-line
Polarized RI nucleus
detectorstopper
Signals from RI detector
ex-NMR method
・ low-yield・ high-contamination・ small-polarization
Difficult to measure !!!!
)Laser spectroscopy & optical detection of RI atoms
Optical pumping in He II
Measure the hyperfine structure
Determination of nuclear moments
Unstale nuclei near the drip-line
Polarized RI nucleus
detectorstopper
Signals from RI detector
ex-NMR method・ low yield・ low purity・ small polarizationDifficult to measure!!
Nuclear moments Nuclear structure
however…
そこで…『 Laser spectroscopy of stopped RI atoms in HeII 』
に着目
Scientific Motivation
目標:短寿命不安定核の系統的核モーメント測定法開発
Conclusion
超流動ヘリウム中でのレーザー・マイクロ波二重共鳴法
・核モーメントを1%以下の精度で決定可能
・ hyperfine anomaly 効果も数%の精度で決定可能
RF 共鳴を用いれば核スピンも決定可能
真空中の値と~5%のズレ → 核内核子の密度分布に対する新しい情報?
理論的には電気四重極モーメントも同時に測定可能
・不安定核ビームを用いた測定・ Al, Mg 原子の光ポンピング
・ HeII の影響について考察~ Next Plan ~
安定核 133Cs, 85,87Rb の超微細構造を測定