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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.

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Takeshi furukawa

International Nuclear Physics Conference 2007 - Jun. 4 -

Hyperfine structure of 85,87Rb and

133Cs atoms in superfluid helium

Development of new laser spectroscopy project

using superfluid helium stopper

Takeshi Furukawa

Nishina-Center, RIKEN

Collaborator

Y. 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.


Contents
Contents

International Nuclear Physics Conference 2007 - Jun. 4 -

1) Our New laser spectroscopy project

・Double resonance method in He II

(

Laser spectroscopy & optical detection

Optical pumping in He II

2) Measurement data in the development

・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

3) Summary and future prospect


Overview of our method
Overview of Our Method

from “DRAEMON” vol. 22, by FUJIKO, F. Fujio

International Nuclear Physics Conference 2007 - Jun. 4 -

Development : laser spectroscopy for short-lived RI atoms

OROCHI project

(tentative)

Optical RI-atom Observation in Condensed Helium

He II liquid

RI atom

purpose

Systematical measurement of

unknown hyperfine structures

in exotic RI atoms

Laser

RI beam

Laser induced fluorescence (LIF)

effective stopping & trapping of RI atoms

wavelength separator

& photon detector

using superfluid helium as a stopper & trap


Nuclear laser spectroscopy
Nuclear Laser Spectroscopy

Contaminated atoms: no absorbing laser light

→observe only objective atoms !!

absorb & emit photons cyclically

→ detect much photons/atom

(typically ~ 105-108 photons /sec)

→good statistic !!

absorption spectra in He II :

largelybroadened & blue-shifted.

wavelength : λatoms≠ λlaser

suppress the detection of scattered laser light

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

He II

Laser

Scattered laser photon

RI beam


Double resonance method
Double Resonance Method

expected spectrum

LIF intensity

microwave frequency

International Nuclear Physics Conference 2007 - Jun. 4 -

Purpose: measure the hyperfine structure of RI atom

Polarized atoms : Can not absorb circularly polarized laser light.

LIF Intensity ∝ 1 - Pz


Spin relaxation in he ii
Spin relaxation inHe II

extremely longer than optical pumping time

International Nuclear Physics Conference 2007 - Jun. 4 -

To polarize the atoms : spin relaxation time is important

long spin relaxation time in He II has been measured.

feasible to achieve optical pumping

133Cs atoms in He II

T. Furukawa et al., Phys. Rev. Lett. 96, 095301 (2006)


Experimental setup
Experimental Setup

International Nuclear Physics Conference 2007 - Jun. 4 -

Measurement of the hyperfine splitting in Cs, Rb atoms

CsI

Cs

Cs


Double resonance peak in he ii
Double resonance peak inHe II

International Nuclear Physics Conference 2007 - Jun. 4 -

Hyperfine resonance measurement :stable 133Cs, 85,87Rb

measured spectrum using double resonance method

ν133Cs= 9.2580915 (4) GHz

ν87Rb= 6.87652 (10) GHz

ν85Rb= 3.05802 (10) GHz

A85Rb = 1.01702(2) GHz

A87Rb = 3.43517(4) GHz

(Preliminary)

A133Cs = 2.312 76(2) GHz

(Preliminary)

(Preliminary)


Hyperfine structure in he ii
Hyperfine Structure inHe II

Pressurized by helium

H’ (> H)

International Nuclear Physics Conference 2007 - Jun. 4 -

H

Calcuration from hyperfine coupling constant

In He II

electron

nuclei

Enable to obtain the nuclear information efficiently!!


For ri beam experiment
for RI Beam Experiment

Wavelength plate

Wavelength plate

Lens

Laser Induced Fluorescence

  (LIF)

Optical filter

Lens

International Nuclear Physics Conference 2007 - Jun. 4 -

to confirm the feasibility of our project

measure the LIF photons from RI atoms

estimated lower limit of the beam intensity to measure:only 10 cps


Conclusion
Conclusion

International Nuclear Physics Conference 2007 - Jun. 4 -

We are now developing successfully…

OROCHI project

(tentative)

Optical RI-atom Observation in Condensed Helium

measure the hyperfine structure of exotic RI atoms

133Cs, 85,87Rb hyperfine splitting in He II

・deduce nuclear moment with 1% accuracy

・deduce hyperfine anomaly with 5% accuracy

* Nuclear spin can be also determined with rf-resonance

~Next plan~

+ RI beam experiment (plan: in next year)

+ Optical pumping of various elements (In, Tl, Ca, ….)

Goal : measurement of In, Tl isotopes


Takeshi furukawa
ふろく

International Nuclear Physics Conference 2007 - Jun. 4 -

Additional OHP


Zeeman sublevels of 85 87 rb
Zeeman sublevels of 85,87Rb

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!

85Rb

87Rb


Pressure effect in he ii
Pressure effect inHeII

Pressurized by helium

H

H’ (> H)

Hyperfine coupling constant

< 1% increase

HeII (GHz)

HeII/vacuum ratio

vacuum (GHz)

133Cs

1.00635(1)

2.31276(2)

2.29815794

ΔCs>ΔRb

1.00505(2)

1.01191092

1.01702(2)

85

Rb

87

1.00522(1)

3.43517(4)

3.41734131

A=mI<H>/I・J

Difference of <H> in He II

Compressed atom by surrounding helium

Affect to the orbital of valence eveltrons

VCs>VRb


Determination of 85 rb moment
Determination of 85Rb moment

Deduce 85Rb moment with 87Rb moment as reference

Use A value in vacuum:

literature value:

・possible to determine the moment with 1% accuracy

・difference (~0.3%) ← caused by hyperfine anomaly

electron

Effect of the distribution of

nuclear magnetization

nuclei


Hyperfine anomaly in he ii
Hyperfine anomaly inHe II

Considering hyperfine anomaly…

hyperfine anomaly

In HeII

)

~5% difference

In vacuum

In HeII

In vacuum

Due to the deformed electron distribution

by the pressure of surrounding He ??


Hyperfine interaction
Hyperfine Interaction

Hyperfine Interaction

W(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)]

A=m<B>/IJ

B=eQ<V>

I:nuclear spin, J:electronic angular momentum,

m: nuclear magnetic dipole moment,

eQ: nuclear electric quadrupole moment,

<B>:magnetic field produced by the electrons

<V>:electric field gradient produced by the electros

Measure the constant A, B of isotope mX and nX

mmX

eQmX

AmX ImX

BmX

=

=

mnX

AnX InX

eQnX

BnX


Effect of surrounding he atoms
Effect of surrounding He atoms

Bubble model

Deform

Energy

absorption

emission

absorption

emission

Deform

Bubble radius

Energy levels in the ground state and excited state

as a function of bubble radius.

① Blue-Shifted

(

absorption spectrum in He II

② Broadened


Excitation spectrum in he ii
Excitation Spectrum in He II

① Blue-Shifted

(

(

absorption spectrum in He II

② Broadened

by the pressure of surrounding He atoms

133Cs atomic spectra in He II

emission:peak ~892 nm, width ~3 nm

(in vacuum: 894.347nm)

Intensity (arb.unit)

absorption:peak ~876 nm, width ~15 nm

absorption≠emission

Wavelength (nm)


Optical merit in he ii
Optical Merit in HeII

① Blue-Shifted

(

(

absorption spectrum in He II

② Broadened

In vacuum

In He II

Laser

Excitation with

only single

laser light

Need many

laser lights!

Detector

wavelength:lLIF≠ llaser

suppress the detection of

scattered laser light

Feasible to acheve optical pumping


Optical pumping
Optical Pumping

P1/2

σ+

σ+

P1/2

D1 Line

X

σ+

σ+

D1 Line

S1/2

X

m = -1/2

m = +1/2

S1/2

m = -1/2

m = +1/2

Optical pumping method

atom

laser

(in the case of alkali atoms J=1/2)

B

After the polarizing of atoms…

Decrease LIF intensity

(Laser Induced Fluorescence, LIF)

LIF Intensity ∝ 1 - Pz


Optical pumping of metastable mg atoms
Optical Pumping of Metastable Mg atoms

21

Mg atomic energy diagram

Observable resonance line

(Assume I

= 5/2

)

3

3s3p

P

F=9/2 ⇔ F=7/2

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]

3

( 3s3p

P

F=7/2 ⇔ F=5/2 )

1


Optical pumping of al atoms
Optical Pumping of Al atoms

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?

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!!


Relaxation in the dark method
Relaxation in the Dark Method

Measure the relaxation time

→“Relaxation in the dark” method

detect the photons only from the “spin relaxed” atoms



Spin relaxation time in he ii
Spin relaxation time in He II

Dark period後のLIF強度

偏極ゼロ時のLIF強度



Demerits in optical detection
Demerits in Optical Detection

Introduced to condenced helium

→ observe all of the stopped atoms

Using the characteristic spectrum of

atoms in He II

high trapping efficiency

→Subtract the problems

Laser

Stopped & trapped

Interaction with surrounding He

RI Beam

Problems in laser spectroscopic study of RI atoms

・possible elements

・stopping & Trapping efficiency

B.G. count of stray light

In He II・・・


Scientific motivation
Scientific Motivation

Laser spectroscopy

& optical detection

of RI atoms

)

Optical pumping in He II

ex) b-NMR method

Measure the

hyperfine structure

detector

stopper

Polarized RI nucleus

Determination of

nuclear moments

detector

Signals from RI

Unstable nuclei near the drip-line

・low-yield

・high-contamination

・small-polarization

Difficult to measure !!!!


Scientific motivation1
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

Nuclear moments Nuclear structure

however…

Unstale nuclei near the drip-line

ex) b-NMR method

・low yield

detector

・low purity

stopper

Polarized RI nucleus

・small polarization

detector

Difficult to measure!!

Signals from RI

そこで…

『Laser spectroscopy of stopped RI atoms in HeII』

に着目


Conclusion1
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

安定核133Cs, 85,87Rbの超微細構造を測定

・核モーメントを1%以下の精度で決定可能

RF共鳴を用いれば核スピンも決定可能

理論的には電気四重極モーメントも同時に測定可能

・hyperfine anomaly効果も数%の精度で決定可能

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?

~Next Plan~

・HeIIの影響について考察

・不安定核ビームを用いた測定

・Al, Mg原子の光ポンピング