H 2 CO
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Transcript of H 2 CO
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H2CO
OHH2O
HCO
QED
e- e-
e- e-
Quantum dipolar gasPrecision test
Chemical reactionsQuantum measurement
Cold and Ultracold Molecules
EuroQUAM, Durham, April 18, 2009
J. Ye, JILA, NIST & CUhttp://jilawww.colorado.edu/YeLabs
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Why ultracold matter?
• We can understand it• We can control it
The most precise measurements ever !
Quantum control, Quantum simulations, Quantum information
Fundamental understandings in condensed matter
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Dipolar quantum systems
Atoms Polar molecules
R+
_
+
_
RMagneticdipoles
Electricdipoles
d ~ Debyed ~ Bohr magneton
e.g. BEC of Crd=6 B
(T. Pfau, Stuttgart)
EI~10-3 - 10-1 nK @ n=1012-1014/cm3
EI~10 - 1000 nK @ n=1012-1014/cm3
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log 10
(den
sity
[cm
-3])
log10(temperature [K])-9 -6 -3 0
3
6
9
12
Dipolar crystal Phase transition
& many-bodyDipolar quantum gasQuantum informationUltracold Chemistry
Molecule optics & circuitryCold controlled chemistry
Novel collisionsFundamental testsPrecision measurement
Science with cold molecules
High density,
Ultracold temperature
~ KBT
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log 10
(den
sity
[cm
-3])
log10(temperature [K])-9 -6 -3 0
3
6
9
12
Stark,magnetic,optical
deceleration
Buffer-gascooling
Photo-association
Coherent statetransfer
Quantumdegeneracy
Enhanced PA?Laser cooling?Sympathetic cooling?Evaporative cooling?
Technology for cold moleculesCarr, DeMille, Krems, & Ye, New. J. Phys. Special Issue (2009).
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• Molecules in single quantum states, under precise control,for internal & external motions
• Unprecedented study of fundamentally important reactions (Dial the rates):
OH + HBr, OH + H2CO, CN + O2, OH + NO, OH + OH, CN + NH3, OH + H
Ultracold molecules: Precision Chemistry
H2CO
OH
H2O
HCO
Controlled molecular collisions Ultracold chemical reactions
Electric field
Stereo-Chemistry
E. Hudson et al.,Phys. Rev. A 73, 063404 (2006).
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Cold ground-state molecules - Stark slower
370 m/s
336 m/s
300 m/s
259 m/s
211 m/s
148 m/s 33 m/s
Bethlem, Berden, Meijer, Phys. Rev. Lett. 83 1558 (1999). Bochinski et al, Phys. Rev. Lett. 91, 243001 (2003).
v
0 = 00
200 300 400
800
550 m/s to rest
1 K to 10 mK
104 – 106 molecules
Density:105 – 107 /cm3
H2CO
OH
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Magnetic trapping of OHSawyer et al., Phys. Rev. Lett. 98, 253002 (2007).
decelerator
Magnetic trap
O
ds
H
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Permanent-Magnet Trap
NdFeB (N42SH) Top = 120oC Bres = 1.24 T
10mm
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Trap Loading
0 V +12 kV -12 kV
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0 V 0 V 0 V
Trap Loading
~ 2 x 106 cm-3
70 mK
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OH
He, D2, NH3 , …
beam source
Ecm ~ 5 cm-1 – 230 cm-1
Quantum threshold collisions Resonant energy transfer
Sawyer et al.,Phys. Rev. Lett. 101, 203203 (2008).
Trap and collisions
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Absolute collision cross sections
Ecm (cm-1)
J = 5/2
J = 3/2
23/2
84 cm-1
OHD2: (1) J = 1 quadrupole moment (2) J = 1 J =3 (300 cm-1)
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Electric Quadrupole guide:
13.5 cm ROC+/- 5 kV~130 m/s ND3
OH Magnet trap
Buffer gas-cooledmolecule source
H
O N
H/D
Ecm < 5 cm-1H/D
H/D
The possibility to probe polar collisions?
Doyle, Rempe, …
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1''13 JX
(a) (b) (c)
(d)
A Molecular MOT ? B. K. Stuhl et al., “A magneto-optical trap for polar molecules,” Phys. Rev. Lett. 101, 243002 (2008).
TiO
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Polar molecules near quantum degeneracy
J. Bohn (JILA), J. Hutson (Durham)
S. Ospelkaus, K.-K. Ni, M. Miranda, B. Neyenhuis, D. Wang, S. Kotochigova, P. S. Julienne,
D. Jin, and J. Ye
KRb molecules
40K Fermions 87Rb Bosons
Temperature ~400nK T/TF=3 Density ~1012/cm3
=0.01 Dipole ~0.5 Debye Long lived (~200ms)
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|f(R)|2
EK
|g(R)|2
|e(R)|2
Laser
Internuclear distance R
En
erg
y
Traditional photo-association
PilletStwalleyHeinzenBigelow… …
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|f(R)|2
EK
Laser
|e(R)|2
|g(R)|2
En
erg
y
Internuclear distance R
Resonant enhancementDeMilleWeidemüller
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|FR(R)|2
|e(R)|2
EK
Laser
Internuclear distance R
En
erg
y
Resonant enhancement – in the ground
Côte
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molecules
>
V(R)
Ebinding
Magneticfield
Colliding atoms
B
RRRR
EnergyEnergy
Magnetic-field Feshbach resonance
Field-tunable scattering resonance
Zirbel et al., Phys. Rev. Lett. 100, 143201 (2008).
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Going to really deep ground potential
The problem – overlap
Laser fields:
1. Impractically strong
2. Nonlinear excitations
GroundElectronic state
PumpDump
Excited electronic
state
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Coherent weak fields to achieve strong field effect
Pump pulseDump
pulse
Wave-packet dynamics bridge the overlap mismatch
Coherent accumulations resolve single quantum state
Pe’er, Shapiro, Stowe, Shapiro, Ye,Phys. Rev. Lett. 98, 113004 (2007).
Excited electronic
state
GroundElectronic state
PumpDump
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1
2
3
1
3
1
Inter-nuclear distance R
Energ
y
v = 0, N = 0, J = 0
Good Franck-Condon for bothup and down transitions.
Excited state is triplet + singlet mixture
Sr
2
1
2
Frequency comb assisted STIRAP
Feshbach + STIRAP Ni et al., Science 322, 231 (2008)
Ospelkaus et al., Nature Phys. 4, 622
(2008)
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JILA Sr optical atomic clocks
Inaccuracy ~ 1 x 10-16
(uncertainty in SI unit of time: 4 x 10-16)
Ludlow et al., Science 319, 1805 (2008). Campbell et al., Science 324, 360 (2009).
Counting the light ripple
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Raman + EIT Dark Resonance
1 scanned, 2 fixed
1 fixed, 2 scanned
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Sta
rk S
hift
(MH
z) B=1.1139(1) GHz
d=0.566(17) Debye
Stark Spectroscopy
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4μs one-way transfer
Coherent Transfer - STIRAP
92% efficiency
No heating
T/TF=2.5
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No Heating in Transfer Process
Direct Imaging of Molecules
0 ms
1 ms
3 ms
6 ms
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Trapped Ground state polar molecules
Trap oscillation
Lifetime ~ 150 ms
EPol
||
Ospelkaus et al., Faraday Discussions 142
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Atom-molecule collisions
3x104 K, =70(10)ms
3x105 K, =6(1)ms
KRb+ K
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KRb+ K KRb+ Rb
=5.4(1.0) 10-11 cm3/s =6.5(1.0) 10-11 cm3/s
Atom-molecule collisions
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A harpoon mechanism? J. Bohn
D. HerschbachJ. Hutson
P. Julienne
ionization energy- electron affinity
(1) Near unity probability loss due to short-range reactions(2) Quantum threshold behavior - long-range potential (van der Waals “Length”) characterizes universal inelastic scattering
Upper bound: 11 x10-11 cm3/s (KRb + K); 7.9 x10-11 cm3/s (KRb + Rb)
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Rb2
KRb
K2
KRb+ K -> K2+Rb+ exothermic
endothermicKRb+ Rb -> Rb2+K-
Atom-molecule collisions
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Nuclear spin states for v = 0, N = 0
We populate a single nuclear spin stateJ. AldegundeJ. Hutson
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Dipolar collision resonance?
Collisions of two ground-state Fermionic polar molecules
Evaporative cooling?
Control of elastic/inelastic collisions?
J. Bohn
U(R
)
(nK
)
Shape or Feshbach?We will know soon.
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• Quantum information (strong dipolar interactions, long coherence time)
• Quantum degeneracy (e.g. BEC) (anisotropic interactions)
• Dipolar phase transition (Condensed matter system)
Ultracold molecules: quantum physics
DeMille, Phys. Rev. Lett. 88, 067901 (2002).H.P. Buchler et al., PRL 98, 060404 (2007). T. Koch et al., Nature Phys. 4, 218 (2008). Micheli, Brennen, Zoller, Nature Physics 2, 341 (2006).
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Special thanks
J. Bohn (JILA) P. Julienne (NIST), S. Kotochigova (Temple), J. Hutson (Durham)
OH and H2CO
B. SawyerB. StuhlM. Yeo
E. Hudson (UCLA)B. Lev (Illinois UC)H. Lewandowski (JILA)J. Bochinski (NC State)
KRb
S. OspelkausK.-K. NiM. MirandaB. NeyenhuisD. Wang
A. Pe’er (Israel)J. Zirbel
Deborah Jin