Breaking van der Waals Molecules with Magnetic Fields

Krems, Roman V.

doi:10.1103/physrevlett.93.013201

Cited by 63 publications

(38 citation statements)

References 21 publications

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“…In one of the early studies Krems showed that weakly bound van der Waals complexes can be dissociated by magnetically tuning a Feshbach resonance. 180 In this case the dissociation occurs through coupling between Zeeman levels of the bound and unbound channels and the magnitude of the coupling is varied by changing the external magnetic field. The possibility of sympathetic cooling of magnetically trapped polyatomic molecules by 1 S 0 -state atoms, including alkaline earth atoms, was explored by Tscherbul et al 181,182 Coupled-channel quantum calculations of He + CH 2 indicate that the collision induced spin-relaxation rate is too slow to cause trap loss.…”

Section: Inelastic Scattering In the Presence Of External Fieldsmentioning

confidence: 99%

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

Balakrishnan

2016

The Journal of Chemical Physics

286

271

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Ultracold molecules offer unprecedented opportunities for the controlled interrogation of molecular events, including chemical reactivity in the ultimate quantum regime. The proliferation of methods to create, cool, and confine them has allowed the investigation of a diverse array of molecular systems and chemical reactions at temperatures where only a single partial wave contributes. Here we present a brief account of recent progress on the experimental and theoretical fronts on cold and ultracold molecules and the opportunities and challenges they provide for a fundamental understanding of bimolecular chemical reaction dynamics. Published by AIP Publishing. [http://dx

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Section: Inelastic Scattering In the Presence Of External Fieldsmentioning

confidence: 99%

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

Balakrishnan

2016

The Journal of Chemical Physics

286

271

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“…(n + 2l + 2)! (a s r) l+1 e −a s r/2 L (2l+2) n (a s r), (20) with a scale factor a s = 10. To assess the quality of this representation, the positive energy eigenstates were used to compute the Ag+He elastic scattering cross section for = 3.…”

Section: Molecular Formationmentioning

confidence: 99%

“…They also play a key role in nonlinear optical phenomena and decoherence of dense atomic and molecular gases 18 . Once formed, the vdW molecules can decay via collision-induced dissociation 19 , chemical exchange 13,15,16 and electronic, vibrational, rotational, and Zeeman predissociation 17,20 . In vdW complexes with small binding energies (such as He-O), the Zeeman predissociation can be controlled with an external 1 arXiv:1104.4973v1 [physics.atm-clus]…”

mentioning

confidence: 99%

Formation and dynamics of van der Waals molecules in buffer-gas traps

Brahms

Tscherbul

Zhang

et al. 2011

Phys. Chem. Chem. Phys.

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We show that weakly bound He-containing van der Waals molecules can be produced and magnetically trapped in buffer-gas cooling experiments, and provide a general model for the formation and dynamics of these molecules. Our analysis shows that, at typical experimental parameters, thermodynamics favors the formation of van der Waals complexes composed of a helium atom bound to most open-shell atoms and molecules, and that complex formation occurs quickly enough to ensure chemical equilibrium. For molecular pairs composed of a He atom and an S-state atom, the molecular spin is stable during formation, dissociation, and collisions, and thus these molecules can be magnetically trapped. Collisional spin relaxations are too slow to affect trap lifetimes. However, 3 He-containing complexes can change spin due to adiabatic crossings between trapped and untrapped Zeeman states, mediated by the anisotropic hyperfine interaction, causing trap loss. We provide a detailed model for Ag 3 He molecules, using ab initio calculation of Ag-He interaction potentials and spin interactions, quantum scattering theory, and direct Monte Carlo simulations to describe formation and spin relaxation in this system. The calculated rate of spin-change agrees quantitatively with experimental observations, providing indirect evidence for molecular formation in buffer-gas-cooled magnetic traps.The ability to cool and trap molecules holds great promise for new discoveries in chemistry and physics [1][2][3][4] . Cooled and trapped molecules yield long interaction times, allowing for precision measurements of molecular structure and interactions, tests of fundamental physics 5,6 , and applications in quantum information science 7 . Chemistry shows fundamentally different behavior for cold molecules 8 , and can be highly controlled based on the kinetic energy, external fields 9 , and quantum states 10 of the reactants.Experiments with cold molecules have thus far involved two classes of molecules: Feshbach molecules and deeply bound ground-state molecules. Feshbach molecules are highly vibrationally excited molecules, bound near dissociation, which interact only weakly at long range, due to small dipole moments. They are created by binding pairs of ultracold atoms using laser light (photoassociation), ac magnetic fields (rf as- . By contrast, ground-state heteronuclear molecules often have substantial dipole moments and are immune to spontaneous decay and vibrational relaxation, making these molecules more promising for applications in quantum information processing 7 and quantum simulation 11 . These molecules are either cooled from high temperatures using techniques such as buffer-gas cooling or Stark deceleration, or are created via coherent deexcitation of Feshbach molecules.This article introduces a third family to the hierarchy of trappable molecules -van der Waals (vdW) complexes. VdW molecules are bound solely by long-range dispersion interactions, leading to the weakest binding energies of any groundstate molecules, on the order of a wavenum...

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“…Our results show that the ground and rotationally excited TiHe molecules can form in cryogenic He buffer gas, opening up the possibility of studying three-body recombination and non-universal physics in the multiple partial wave regime [27,46]. The chemical reactions, inelastic scattering, and Zeeman predissociation of cold vdW molecules can now be investigated experimentally and possibly controlled with external electromagnetic fields [22]. This work could also be extended to explore the formation of larger clusters (such as TiHe 2 trimers) at higher helium densities.…”

mentioning

confidence: 97%

“…Recent groundbreaking advances in the production and trapping of translationally cold molecules [16] made it possible to create trapped ensembles of cold polar molecules with high enough densities to study collisions and chemical reactions [16][17][18] and carry out ultra-precise spectroscopic measurements to probe the physics beyond the Standard Model [19]. The production and trapping of cold vdW molecules would similarly enable highly sensitive spectroscopic detection of heretofore unobserved clusters, as well as the study and control of their quantum dynamics [7,[20][21][22].We have recently observed the formation of cold, ground-state LiHe molecules in a cryogenic He buffer gas [23]. The LiHe molecule has a single near-threshold bound state with a binding energy of 0.024 cm −1 [24] comparable to that of the He 2 dimer [11,21].…”

mentioning

confidence: 99%

Cold Anisotropically Interacting van der Waals Molecule: TiHe

et al. 2017

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We have used laser ablation and helium buffer-gas cooling to produce the titanium-helium van der Waals molecule at cryogenic temperatures. The molecules were detected through laser-induced fluorescence spectroscopy. Ground-state Ti(a 3 F2)-He binding energies were determined for the ground and first rotationally excited states from studying equilibrium thermodynamic properties, and found to agree well with theoretical calculations based on newly calculated ab initio Ti-He interaction potentials, opening up novel possibilities for studying the formation, dynamics, and non-universal chemistry of van der Waals clusters at low temperatures.PACS numbers: 34.50. Lf, 33.15.Fm, Weakly bound complexes of atoms and molecules held together by long-range van der Waals (vdW) forces are key to understanding a wide range of phenomena in physics and chemistry, ranging from classical and quantum chaos [1] and phase transitions [2] to the universal physics of Efimov trimers and quantum droplets [3][4][5]. In condensed-phase chemical physics, vdW clusters serve as a model to study the mechanisms of solvation, nucleation, and chemical reactivity [6][7][8]. In the context of quantum many-body physics, vdW molecules can be used to explore the formation of exotic quasiparticles in superfluid helium nanodroplets [9]. Helium-containing vdW molecules are the lightest of all vdW clusters, and hence are of particular interest as model systems, in which to study the emergence of macroscopic quantum phenomena such as superfluidity [10].Thus far, the experimental study of He-containing vdW molecules has focused on molecules formed in supersonic expansions [8,[11][12][13][14][15]. Recent groundbreaking advances in the production and trapping of translationally cold molecules [16] made it possible to create trapped ensembles of cold polar molecules with high enough densities to study collisions and chemical reactions [16][17][18] and carry out ultra-precise spectroscopic measurements to probe the physics beyond the Standard Model [19]. The production and trapping of cold vdW molecules would similarly enable highly sensitive spectroscopic detection of heretofore unobserved clusters, as well as the study and control of their quantum dynamics [7,[20][21][22].We have recently observed the formation of cold, ground-state LiHe molecules in a cryogenic He buffer gas [23]. The LiHe molecule has a single near-threshold bound state with a binding energy of 0.024 cm −1 [24] comparable to that of the He 2 dimer [11,21]. Due to their vanishingly small binding energies, these molecules belong to an exotic class of quantum halo dimers characterized by extremely delocalized wavefunctions, universal properties, and enormously large three-body formation rates [3,25]. As the binding energies of most other * weinstein@physics.unr.edu; http://www.physics.unr.edu/xap/ atoms and molecules with He are much larger than those of LiHe and He 2 [7], it is far from obvious whether atomHe vdW clusters would form upon immersing the parent atoms into cryogenic He buffer gas. ...

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Breaking van der Waals Molecules with Magnetic Fields

Cited by 63 publications

References 21 publications

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

Formation and dynamics of van der Waals molecules in buffer-gas traps

Cold Anisotropically Interacting van der Waals Molecule: TiHe

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