Photoassociation Spectroscopy of Ytterbium Atoms with Dipole-allowed

and Intercombination Transitions

K. Enomoto, M. Kitagawa, K. Kasa, S. Tojo, T. Fukuhara, A. Yamaguchi, S. Uetake, Y. Takasu, and Y. Takahashi, Kyoto University

Ultracold Group II atoms: Theory and Applications 06/Sep/18 ITAMP

についての COE 報告会

YtterbiumYtterbium

Group IIGroup II

Workshop on ultracold group II atoms

2000 Cold Alkaline-Earth Atoms (in ITAMP)

2003 Cold Alkaline-Earth Atoms (in Copenhagen)

2006 Sep/18-20 Ultracold Group II Atoms (in ITAMP)

Atomic clock

Number of invited speakers

Experiment Theory

Photoassociation

Novel species/mixtures

Others

4 1

4 5

5 1

3 5

Next generation atomic clock

1S0-3P0 atomic transition has extremelynarrow linewidth ( <0.1 Hz), and is inert to a magnetic field. The atoms trapped in an optical lattice with the magic wavelength are free from the Doppler broadening and the collisional shift.

Frequency standard with / ~ 10-17

Precise frequency measurements of Sr and Yb in 1D latticehave been presented (NIST, JILA, SYRTE, PTB groups).

The precision is about 5Hz.

R

g

Photoassociation (PA)

Ultracold atoms has narrow thermal distribution, so free-boundtransitions (photoassociation) areobserved with high resolution.This photoassociation is a powerfultool for probing rovibrational levelsnear the threshold and scattering states.

Such parameters are determined for Sr, Ca, and Yb.

Atomic parameters such asradiative lifetimes and scatteringlengths are determined precisely.

Theory for optical control of collision, PA in low dimensions

Novel species/mixtures

Magneto-optical trap (MOT) of Ra (radium, =15day)

Measurement of nuclear EDM

MOT of Li-K-Sr mixture

Novel cooper pair (heteronuclear,FFLO, etc.)

Summary of my talk

Level Diagram of Yb

(6s6p)1P1

(6s2)1S0

intercombination transition556 nm, =874ns (Linewidth=182kHz)

(6s6p)3P2

3P13P0

clock transition

dipole allowed, 399 nm=5.5ns (Linewidth=29MHz)

Mass number

Nuclear spin i

Abundance(%)

168

0

0.13

170

0

3.05

171

1/2

14.3

172

0

21.9

173

5/2

16.2

174

0

31.8

176

0

12.7

=15s

~

Outline

1. Experimental procedure

2. Determination of scattering length of 174Yb

3. Two-color PAS

4. Intercombination PAS of 4 isotopes

5. Optical Feshbach resonance

atomicbeam

Zeeman slower

Experimental procedure

399 nmZeeman slowing laser ( ～ 40 mW)

anti-Helmholtzcoils

556 nmMOT laser ( ～ 30 mW each)

slower

MOT

horiz. FORT

vertical FORT

PA

probe

～ 10s

～ 6s

～ 100ms

Typical time chart

Experimental procedure

CCD camera

absorption image

532 nmFORT laser

(7→0.2 W, 0= 12 m) (7 W 0= 80 m)

399 nmprobe laser

( ～ 0.01W/cm2)

556 nmPA laser

( ～ 0.1W/cm2)slower

MOT

horiz. FORT

vertical FORT

PA

probe

～ 10s

～ 6s

～ 100ms

Typical time chart

Off resonance

240m

1.0

0.0tran

smis

sion

On resonance

N ~105

n ~1014 cm-3

Determination of scattering length of 174Yb using dipole-allowed PAS

Spectra of dipole-allowed PAS

10 15 20 25 30 350

5

10

345170 175 180 1850

5

10

98103

108

110 113116 118

Detuning (GHz)

Nu

mb

er

of

ato

ms

(10

4 )

156157 158

175

PAS of 1S0-1P1 transition at ~1 K

Ground-state wavefunction

Wavefunction obtained from PA rates to various vibrational states

3 4 5 6 7 8 9 10 113 4 5 6 7 8 9 10 113 4 5 6 7 8 9 10 11

1

10

Squ

ared

wav

e fu

nctio

n (a

rb. u

nits

)

Internuclear distance (nm)

Scattering length a of 174Yb is 5.53 0.11 nm

C6 potential coefficient is 2300 250 a.u.

(with taking account of other sources of error.)

Two-color PAS

Two-color PA spectra of 174Yb

120000

80000

40000

0

Num

ber

of a

tom

s

10.710.610.510.410.310.2

Frequency deference (MHz)

Raman transition

Recently, we succeededin observing two-colorPAS spectra for 174Yb at ~1 K.

12

174Yb 1S0-1P1

Frequency difference (MHz)

Last bound state level 10.63 MHz

11.0

10.8

10.6

10.4

10.2

10.0

f2-f

1 (

MH

z)

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2

f (MHz)

Lightshift

Expected shift (MHz)

Two-color PA spectra of 174Yb

Next-to-the-last state level 268.6 MHz

12

120000

80000

40000

0

Nu

mb

er

of

ato

ms

269.2269.0268.8268.6268.4268.2

Frequency deference (MHz)Frequency difference (MHz)

120000

100000

80000

60000

40000

20000

0

Nu

mb

er

of

ato

ms

360320280240200160

Frequency difference (MHz)

Dark state (1 is scanned)

Autler-Townes spectroscopy(2 is scanned)

These two-color PASresults determine C6 and a more precisely.

Scattering length of other isotopes

)]8

tan(1[

aa

iR

dRRmV )(21

Gribakin et al., PRA 48, 546 (1993).

The scattering length a can be described with the phase .

Two-color PA spectroscopy of some isotopes will reveal the scattering lengths of all the isotopes and their combinations.

Scattering length

pos. 6 nmsmallneg. ?small small? large?

+10- 5

Mass number 168 170 171 172 173 174 176

~54 Å

Scattering length ~54 Å? Å

Mass number 168 170 171 172 173 174 176

? Å ? Å ? Å ? Å ? Å

Intercombination PAS of bosonic (i=0) isotopes (174Yb, 176Yb )

PA spectrum of 174Yb

v’ = 8v’ = 9

v’ = 10 v’ = 7T ~ 4 K

At a low temperature of~4 K, only transitionfrom s-wave scatteringstate was observed.

Even the vibrational levelat 3 MHz from the disso-ciation limit was resolved.

v’ : vibrational number counted from the dissociation limit.

PA spectra of 174Yb & 176Yb (T~25 K)

174Yb

Je = 1

Je = 1

Je = 1

Je = 3

Je = 3

Je = 3

v’ = 16

v’ = 14

v’ = 10

RC=6.5 nm

RC=8.6 nm

RC=17.4 nm Je = 1

Je = 1

Je = 3

Je = 3

Je = 1

Je = 3

v’ = 16

v’ = 13

v’ = 10

RC= 6.0 nm

RC= 9.0 nm

RC=15.1 nm

176Yb

Large difference in signal intensity

Difference between 174Yb & 176Yb

The PA efficiency for Je=3 line of 174Yb is large inside the centri-fugal potential barrier.

This is due to shape resonance.

wavefunction near shape resonance

d-wave potential

wavefunction far fromshape resonance

Intercombination PAS of fermionic (i0) isotopes (171Yb, 173Yb )

L

S JaI

F

T

hyperfine coupling coupling to molecular axis

Potential calculation

B111

3

A201

B201

A1113 ,PSS,P ff

B111

3

A201

B201

A1113 ,PSS,P ff

iiii islf

21 ffF

,

)(3

221132121 jijia

r

ddddH zz

iii slj

id

:transition dipole, a:hyperfine coupling constant

171Yb (3P1) ‥ i =1/2, j =11S0, f1=1/2

3P1, f2=3/2,1/2

basis sym.:

basis antisym.:

,i and are projection of and to molecular axis, respectively.if

F

,

i

i

j

f(1S0) ‥ i =1/2, j =0

Pair potential of 171Yb2 [1S0+3P1(f=3/2)]

Hyperfine-induced purely long-range states exist.

2 4 6 8 10 12 14-1200

-1000

-800

-600

-400

-200

0

200

En

erg

y (M

Hz)

Internuclear Distance (nm)2 4 6 8 10 12 14

-1200

-1000

-800

-600

-400

-200

0

200

En

erg

y (M

Hz)

Internuclear Distance (nm)

F = 1, = 0 = 2

= 1

= 1

F = 2, = 0

state sym.: state antisym.:

s,d-wavep,f-wave

f=3/2 f=3/2

20000

15000

10000

5000

0Nu

mb

er

of A

tom

s

-280 -260 -240 -220 -200

Frequency Detuning (MHz)

PA spectrum of 171Yb

p waves wave

T=1T=2 T=3 T=1 p s

purely long-range state

-400 0-1000 -200-800 -600

f =3/2

(MHz)

-1060MHz ~ -160MHz

Temperature ~20 K

p

ConclusionPAS with the intercombination transition

d-wave shape resonance is inferred for 174Yb.Hyperfine-induced purely long-range state was observed.

PAS with the dipole-allowed transitiona = 5.53 ± 0.11 nm, C6 = 2300 ± 250 nm for 174Yb

Two-color PAS of 174YbBound levels at 10.6 MHz and 268.6 MHz were found.

Optical Feshbach resonance with the intercombination line

The asymmetric spectrum implies the change of a.

3P2 state atoms are trapped in the optical trap with high density.

Quantum degenerate gases have been achieved for 5 isotopes.