Laser spectroscopy of radioactive atoms embedded in superfluid He ,

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


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


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.



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


Experimental SetupExperimental Setup


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


(Laser induced fluorescence)


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)


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


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


・ 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.


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 )


Our achievementOur achievementOur achievementOur achievement

Off-line development with stable isotope

・ determine nuclear spin & moment : Cs, Rb isotopes


・ 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



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.


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.


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Laser spectroscopy of radioactive atoms embedded in superfluid He ,