(ultra-)cold molecules what difference does a (micro-)kelvin make? olivier dulieu laboratoire aimé...
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(Ultra-)Cold Molecules
What difference does a (micro-)Kelvin make?
Olivier DulieuLaboratoire Aimé Cotton, CNRS, Campus d’Orsay, Orsay, France
(Ultra-)Cold Molecules
What difference does a (micro-)Kelvin make?
Olivier DulieuLaboratoire Aimé Cotton, CNRS, Campus d’Orsay, Orsay, France
Molecules are really cool!• « The subtle flirtation of ultracold atoms »,Science, 280, 200 (1998): « If
high-energy accelarators make the rap music of physics-with their whirling particles and rapid-free smashups, then collisions between ultracold atoms are its Wagnerian opera »
• « Molecules are cool », J. Doyle&B. Friedrich, Nature 401, 749 (1999): « Under ordinary conditions, atoms and molecules of a gas zigzag in all directions…[and] are most likely to move at the speed of riffle bullets… The emergence of methods for slowing and trapping gaseous species has lead to a renaissance in atomic physics, which is now progressing into molecular/chemical physics as well… Just as atom cooling is opening up new avenues of research, it is likely that the same will happen with molecular cooling – with repercussions for chemistry, and even, perhaps, in biology. »
• « Hot prospects for ultracold molecules », B. Goss Levi, Physics Today, Sept. 2000, p.46
• « Quantum encounters of the cold kind », K. Burnett, P.D. Lett, E. Tiesinga, P.Julienne, C.J. Williams, Nature 416, 225 (2002) « We have already seen our dreams of controlling interactions on the quantum level come true, and the exquisite nature of this control has proved remarkable. These achievements have come from experimental and theoretical developments that have been a joy to be involved in, and their impact on new physics, chemistry and quantum computation has only just begun.
• « Really cool molecules », P. S. Julienne, Nature, 424, 24 (2003)
(Envisioned?) Applications of cold molecules
• Ultra-high resolution spectroscopy • Test of fundamental theories • Superchemistry • Ultracold Photochemistry • Quantum properties, BCS, superfluidity• Ultimate control of reactive collisions• Quantum information• Biology…• …
Ultra-high resolution spectroscopy (1)
Accurate determination of the van der Waals coefficient in Cesium
100 high-lying levels
66 / RC
Atomic radiative lifetime from molecular spectroscopy data
Ultra-high resolution spectroscopy (2)
Ultra-high resolution spectroscopy (3)
Accurate spectroscopy of a Feshbach resonance in 85RbUsing coherent atom-molecule oscillations in a BEC
We precisely measured the binding energy of a molecular state near the Feshbach resonance in a 85Rb Bose-Einstein condensate. Rapid magnetic-field pulses induced coherent atom-molecule oscillations in the BEC. We measured the oscillation frequency as a function of B field and fit the data to a coupled-channel model. Our analysis constrained the Feshbach resonance position @155.041(18) G, width 10.71(2) G, and background scattering length 2443(3)a0 …
2220 42sin)exp()( tAtNtN avg
Test of fundamental theories: Electron dipole moment with heavy polar molecules
Effective electric field seen by the valence electron:
eff=Q P
structure
Degree of polarization due to an external field; moderate for a polar molecule
Interaction energy: V=-de. eff
Quantum information
p.067901
Phys. Rev.Lett. 84, 5029 (2000)
Superchemistry: they dreamed about it….
Superchemistry: they made it!
Vol 417, p529 (2002)
BEC-BCS crossover
Cold and trapped molecular ions: toward complete control of chemical reactions?
Atomic ions
(from M. Drewsen, private communication)
Reaction experiments24Mg+(3p) + H2 -> 24MgH+ + H
Beforereactions
Afterreactions
24Mg+
26Mg+
24MgH+
26Mg+
24Mg+
From M. Drewsen, private communication, and MOLEC XIV
Outline of this week’ lectures
• 1- Introduction, overview• 2- Hamiltonian of a diatomic
molecule• 3- Hund’s cases; Molecular
symmetries• 4- Molecular spectroscopy• 5- Photoassociation of cold atoms• 6- Ultracold (elastic) collisions
References
• H. Lefebvre-Brion&R.W. Field, « The Spectra and Dynamics of Diatomic Molecules », Elsevier Academic Press, 2004
• G. Herzberg, « The Spectra od Diatomic Molecules », Van Nostrand-Reinhold, Princeton, 1950, reprinted in 1989 by Krieger, Malabar.
• Tutorials from G. Amat (Paris), A. Beswick (Orsay), C. Jungen (Orsay)
• Bibliographic Databases:– DiRef: a bibliographic database for diatomic molecules, J. Mol.
Spectrosc. 207, 287 (2001); http://diref.uwaterloo.ca– Cold Molecules: http://www.lac.u-psud.fr/coldmolecules, in
progress
The Cold Molecule Network COMOLHPRN-CT-2002-00290
São Pedro 2004…
Heidelberg 2002Les Houches 2002
…Boulder 1997
…Telluride 1994
Lago di Como 1989
http://www.lac.u-psud.fr/coldmolecules
Outline of this week’ lectures
• 1- Introduction, overview• 2- Hamiltonian of a diatomic
molecule• 3- Hund’s cases; Molecular
symmetries• 4- Molecular spectroscopy• 5- Photoassociation of cold atoms• 6- Ultracold (elastic) collisions
Laser Cooling of Molecules…not so cool!
• Another solution: photoassociation of cold atoms…
A novel scheme is proposed for sequential cooling of rotation, translation, and vibration of molecules. More generally, this scheme manipulates and controls the states and energies of molecules. The scheme, while somewhat complex, is simpler and more feasible than simply providing a large number of synchronously but independently tunable lasers. The key component is a multiple single frequency laser in which a single narrow band pump laser generates an ensemble of resonant ‘‘stimulated Raman’’ sidebands subsequently amplified and selected in a sample of the molecules to be cooled….Only this specific order of rotation–translation–vibration appears feasible (using molecules produced by photoassociation of ultracold atoms avoids the requirement for translational cooling). Each step employs true dissipative cooling … by spontaneous emission and should yield a large translationally cold sample of molecules in the lowest v=0, J=0 level of the ground electronic state…
Other theoretical approaches:Optimal Control Theory
• Thermodynamical analysis of the cooling of internal degrees of freedom: see A.Bartana & R.Kosloff, J. Chem. Phys 99, 196 (1993)
• Numerical application (at LAC): C. Koch et al, Phys. Rev. A 70, 013402 (2004) « Stabilization of ultracold molecules using optimal control theory)
Shaped pulse laser
Initial (cold) molecule in high v
Transfer to v=0
Intermediate excited state
Direct laser cooling of BeH, CaHDiRosa et al@Los Alamos
Rydberg transitions similar to the D1, D2 in alkali atoms(Nearly) Diagonal Franck-Condon matricesGood spectral isolation suitable for Doppler cooling
Under progress
Photoassociation of cold atoms+stabilization
Cs2: Orsay, PRL, 80, 4402 (1998); Rb2: Pisa, PRL, 84, 2814 (2000)
• transfer density of probability inwards,
• to produce deeply-bound ultracold molecules
• See lecture on Thursday
Alternative methods for cooling molecules
• Stark deceleration (2000)• Buffer gas cooling (1998)• Expansion out of a rotating nozzle (2004)• Phase space filtering (2004)• Billiard like collisions (2003)• Doped helium droplets (1992)• Feshbach resonances in a BEC (2003)• Reactive collisions (proposal in 1992)
Stark deceleration(G. Meijer@Berlin, E.
Hinds@London)Bethlem et al, Nature 406, 491 (2000), Int. Rev.
Phys. Chem. 22, 73 (2003)
Buffer gas cooling (J. Doyle@Harvard, A.
Peters@Berlin)
Weinstein et al, Nature 395, 148 (1998)
Expansion out of a rotating nozzle • M. Gupta & D. Hershbach, J. Phys.Chem A 105, 1626 (2001)• Zhao et al, Rev. Sci. Instr. 75, 146 (2004)
Phase space filtering (G. Rempe@Garching)
Phase space filtering (G. Rempe@Garching)
Billiard-like collisions (D. Chandler@Sandia Labs)
• Elioff et al, Science 302, 1940 (2003)
Other techniques under progress (1)
Other techniques under progress (2)
Doped helium droplets (F. Stienckemeier@Bielefeld, G. Scoles@Princeton)
• Mudrich et al, Eur. Phys. D (2004); Lewenrenz et al, J. Chem. Phys. 102, 8191 (1995)
Pick up cell technique
Toennies et al, Physics Today 54, p31 (2001)
Na2 on the surface of 104 4He atom droplets
T=2.7K
Excitation spectra of the dimers
Feshbach molecules