Takeshi Furukawa

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


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


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, ….


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


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


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


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!!


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


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, ….)


Goal : measurement of In, Tl isotopes

Additional OHPAdditional OHP


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

Takeshi Furukawa

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