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Experiments with ultracold RbCs molecules. Cs. Rb. Peter Molony. 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. Caesium. - PowerPoint PPT Presentation
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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
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
87RbCs STIRAP
L.P. Yatsenko et al., PRA 65, 043409 (2002)
S P
SP
1
2
3
Relative linewidth of the two lasers D
Peter Molony - YAO 20142014-04-02
87RbCs STIRAP
L.P. Yatsenko et al., PRA 65, 043409 (2002)
Narrow linewidth
High intensity Intensity control
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
87RbCs STIRAP optical setup
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
Ground state spectroscopy
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
Last time
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
Last time
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
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)
Peter Molony - YAO 20142014-04-02
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))
Peter Molony - YAO 20142014-04-02
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
Peter Molony - YAO 20142014-04-02
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 ???
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