experiments with ultracold rbcs molecules

Experiments with ultracoldRbCs molecules

Peter Molony

Cs Rb

Peter Molony - YAO 20142014-04-02

The RbCs team: Peter Molony, Phil Gregory, Michael Koeppinger,Zhonghua Ji, Bo Lu and Simon Cornish (PI)

Theory: Caroline Blackley, Ruth Le Sueur, Jeremy Hutson


Goal: A quantum array of polar molecules

Mott Insulator Transition

Convert to ground stateRbCs molecules

Jaksch et al., PRL 89, 040402 (2002)Damski et al. PRL 90, 110401 (2003)

Rubidium Caesium

RbCs: Stable against reactive collisionsd = 1.25 D, Brot = 0.5 GHzInduced deff = d / 3 for E = Brot / d = 0.8 kV / cm


The experiment

Dipole trap loaded byreducing field gradient

Atoms collected in MOT Evaporation in quadrupole trap

Load quadrupole trap

Levitated dipole trap

Apply a magnetic gradient to tilt the trap

Reduce the beam intensityto lower the trap depth

kT

RF

2-species BEC!

Phys. Rev. A 87 013625 (2013)


The experiment

1. Create a high phase space density atomic sample.

6S1/2

X1S+

a3S+

(1)3P

Deeply Bound Molecule

FeshbachMolecule

FreeAtoms

~1560nm

~980nm

Magneto-association

Stimulated RamanAdiabatic Passage

2. Associate weakly-bound molecules via a Feshbach resonance.

3. Transfer Feshbach molecules to the rovibrationalground state using stimulated Raman adiabatic passage (STIRAP).

Pote

ntia

l Ene

rgy

Convert atomsto molecules

AtomicState

MolecularBound State

Magnetic Field (B)


87RbCs trapping

~4000 optically trapped molecules

0 50 100 150 2000

1

2

3

4

5x103

M

olec

ule

Num

ber

Time (ms)

0 4 8 12 16 20

Lase

rP

ower

Time (ms)

Mag

netic

Gra

dien

t

Off

200 mW

Off

Off100 mW

44 G/cm29 G/cm

181 G

250 G/s197.5 G

22 G

Bia

s Fi

eld

212 G

Phys. Rev. A 89 033604 (2014)Cs Rb


87RbCs STIRAP

L.P. Yatsenko et al., PRA 65, 043409 (2002)

S P

SP

1

2

3

Relative linewidth of the two lasers D


87RbCs STIRAP

L.P. Yatsenko et al., PRA 65, 043409 (2002)

Narrow linewidth

High intensity Intensity control


87RbCs spectroscopy

Figure: M. Debatin, PhD Thesis, Innsbruck (2013)Data: S. Kotochigova and E. Tiesinga,

J. Chem. Phys. 123, 174304 (2005)

O. Docenko et al., PRA 81, 042511 (2010)

STIRAP: W.C. Stwalley, EPJD 31, 221-225 (2004)

Excited state with mixed singlet – triplet character

Good Franck–Condon overlap for both transitions

Our laser: 6330 → 6711 cm-1

Find suitable intermediate state


87RbCs STIRAP optical setup

1556 nm

980 nm

EO

M

EOM

980 nm DL Pro

Cavity

Cavity

Wavemeter

Experiment

Experiment

EO

M

1556 nm DL Pro

Fibre Coupler

l/2 Waveplate

l/4 Waveplate

Optical Isolator

Polarising Beam Splitter

Glan-Thompson Polariser

AOM

Shutter

Dichroic Mirror

Photo Diode

Mol

ecul

es

1556

nm

980

nm


87RbCs STIRAP optical setup


87RbCs spectroscopy

7 transitions found so far: v’=38 J’=3 192560.47(2) GHzv’=38 J’=1 192556.62(2)v’=37 J’=1 191827.53(2)v’=35 J’=1 190789.15(2)v’=29 J’=3 192577.55(2)v’=29 J’=2 192574.54(2)v’=29 J’=1 192572.09(2)


Ground state spectroscopy


Ground state rotational constant

Brot = 0.016352(1) cm-1 = 490.23(4) MHzTheory = 0.016(3) J Phys Chem A 116,11101 (2012)v=1 state 50 cm-1 higher


Outlook

• 4000 87RbCs molecules in optical dipole trap.

• Magnetic moment of 87RbCs in different internal states measured.

• Spectroscopy on electronically excited states.

• Absolute ground state found by spectroscopy.

• Setup ready for STIRAP.

Summary

Cs Rb


Outlook

• Measure dipole moment of ground state 87RbCs molecules (electrodes ready)

• Transfer molecules into absolute ground state (STIRAP)

• Produce 85RbCs molecules in new dipole trap

• New experimental setup

Outlook

Phys. Rev. A 87 010703(R) (2013)


Goal: A quantum array of polar molecules

Mott Insulator Transition

Miscible Immiscible

Convert to ground stateRbCs molecules

U12 < (U11 + U22)/2 U12 > (U11 + U22)/2

Jaksch et al., PRL 89, 040402 (2002)Damski et al. PRL 90, 110401 (2003)

Rubidium Caesium

RbCs: Stable against reactive collisionsd = 1.25 D, Brot = 0.5 GHzInduced deff = d / 3 for E = Brot / d = 0.8 kV / cm


Last time

0 10 20 30-10

-5

Ene

rgy

/ h (M

Hz)

Magnetic Moment (G)

-2

-1

0

1x103

6g(2

)6g

(3)

6g(4

)

4g(2

)

6g(5

)4g

(3)

4g(4

)

-7(4

4)6s

(6) -2(33)6g(6)

S

catte

ring

Leng

th (a

0)

-1(33)6s(6)

Cs2 Feshbach molecules


Last time

0 10 20 30-10

-5

Ene

rgy

/ h (M

Hz)

Magnetic Moment (G)

-2

-1

0

1x103

6g(2

)6g

(3)

6g(4

)

4g(2

)

6g(5

)4g

(3)

4g(4

)

-7(4

4)6s

(6) -2(33)6g(6)

S

catte

ring

Leng

th (a

0)

-1(33)6s(6)


Last time


Last time

0 10 20 30-10

-5

Ene

rgy

/ h (M

Hz)

Magnetic Moment (G)

-2

-1

0

1x103

6g(2

)6g

(3)

6g(4

)

4g(2

)

6g(5

)4g

(3)

4g(4

)

-7(4

4)6s

(6) -2(33)6g(6)

S

catte

ring

Leng

th (a

0)

-1(33)6s(6)


Last time


Magnetic moment

0 10 20 30-10

-5

Ene

rgy

/ h (M

Hz)

Magnetic Moment (G)

-2

-1

0

1x103

6g(2

)6g

(3)

6g(4

)

4g(2

)

6g(5

)4g

(3)

4g(4

)

-7(4

4)6s

(6) -2(33)6g(6)

Sca

tterin

gLe

ngth

(a0)

-1(33)6s(6)

10.0 12.5 15.0 17.5-1.6

-1.4

-1.2

-1.0

-0.8

6g(6)-1.5

B

Mag

netic

Mom

ent ( B

)

Magnetic Field (G)

4g(4)-0.9

B


Magnetic moment

10.0 12.5 15.0 17.5-1.6

-1.4

-1.2

-1.0

-0.8

6g(6)-1.5

B

Mag

netic

Mom

ent ( B

)

Magnetic Field (G)

4g(4)-0.9

B


Trapped Cs2 molecules

0

2

4

6

8x103

Hor

izon

tal

Wid

th (

m)

Mol

ecul

e N

umbe

r

Time (s)0.0 0.3 0.6 0.9 1.2

20

40


87RbCs Feshbach molecules180 182 184

0

2

4

6

8x104

196.5 197.0 197.5

500

700

900

Magnetic Field (G)

Ene

rgy

/ h (M

Hz)

Sca

tterin

gLe

ngth

(a0)

Magnetic Field (G)

133 C

s N

umbe

r

175 180 185 190 195 200-4

-2

0

|-6(2,4)d(2,3)> +1.7B

|-1(1,3)s(1,3)> -1.3B

|-6(2,4)d(2,4)> +2B

|-2(1.3)d(0,3)> -0.9B

(c)

(b)

(a)


87RbCs Feshbach Molecules

Cs Rb

~5000 RbCs molecules

0 4 8 12 16 20

Lase

rP

ower

Time (ms)

Mag

netic

Gra

dien

t

Off

200 mW

Off

Off100 mW

44 G/cm29 G/cm

181 G

250 G/s197.5 G

22 G

Bia

s Fi

eld

212 G

180 182 1840

2

4

6

8x104

196.5 197.0 197.5

500

700

900

Magnetic Field (G)

Ene

rgy

/ h (M

Hz)

Sca

tterin

gLe

ngth

(a0)

Magnetic Field (G)

133 C

s N

umbe

r

175 180 185 190 195 200-4

-2

0

|-6(2,4)d(2,3)> +1.7B

|-1(1,3)s(1,3)> -1.3B

|-6(2,4)d(2,4)> +2B

|-2(1.3)d(0,3)> -0.9B

(c)

(b)

(a)


RbCs moleculesMagnetic moment measurement

Keep molecules in the same position since the magnetic moment changes while the molecules are falling

• Vary magnetic field gradient• Measure position after different period of time

mol ,181G = -0.84(1) B

-0.500 -0.496 -0.492 -0.488 -0.484

300

320

340

360

50msY = A + B * XA 2000(64)B 3400(131)

30msY = A + B * XA 1068(33)B 1495(68)

V p

ositi

on (p

ix)

Levitation field VcMT (V)180.5 181.0 181.5 182.0 182.5 183.0

-1

0

1

2

-4

-2

0

Mag

netic

mom

ent ( B

)

Magnetic field (G)

Bin

ding

Ene

rgy

(MH

z)


87RbCs magnetic moment

180 181 182 183 184 185-1.50

-0.75

0.00

0.75

1.50

High-FieldSeeking

Mag

netic

Mom

ent ( B

)

Magnetic Field (G)

Low-FieldSeeking

180 182 1840

2

4

6

8x104

196.5 197.0 197.5

500

700

900

Magnetic Field (G)

Ene

rgy

/ h (M

Hz)

Sca

tterin

gLe

ngth

(a0)

Magnetic Field (G)

133 C

s N

umbe

r

175 180 185 190 195 200-4

-2

0

|-6(2,4)d(2,3)> +1.7B

|-1(1,3)s(1,3)> -1.3B

|-6(2,4)d(2,4)> +2B

|-2(1.3)d(0,3)> -0.9B

(c)

(b)

(a)


Next step

RbCs excited state spectroscopy

Excited state potential through Fourier transform spectroscopy (FTS)(O. Docenko et al., PRA 81, 042511 (2010))

Ground state potential measured using laser-induced fluorescence combined with Fourier transform spectroscopy (LIF-FTS)(C.E. Fellows et al., J. Mol. Spectrosc. 197, 19 (1999))


Next step

RbCs excited state spectroscopy

M. Debatin et al., Phys. Chem. Chem. Phys. 13, 18926 (2011)

Resonances at ~ 1556 nm

DFWHM ~ 2p x 5 MHz


First identify a suitable intermediate state with sufficient oscillator strength with bothconnected levels

Excited state potential from PRA 81, 042511 (2010)Ground state potential from J. Mol. Spectrosc. 197, 19 (1999)

Single photon excited state spectroscopy:• Irradiate molecules only with L1 for 10 s to 10 ms • Gamma can be calculated detuning the laser• Rabi frequencies can be calculated using the decay during irradiation

Two photon dark state resonance spectroscopy:• Simultaneous irradiation with rectangular light pulses of L1 and L2• 10 – 100 s irradiation time• L2 << L1 (more 980 nm light)• Vary detuning of L1 (1550 nm) and keep L2 in resonance

How do I know DL2 = 0 ???

experiments with ultracold rbcs molecules

Documents

state molecules

csrbpeter molony yao

lasers dpeter molony

final state

heteronuclear molecules

trapped molecules

mott insulator state

rovibrationalground