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Viewpoint: From atoms to molecules (and back)

Simon L. Cornish

Published Sep 25, 2008• 0 citations
OpenAlex

Abstract

Atoms colliding in a magnetic field can form weakly bound states called Feshbach molecules. These states have now been used in combination with advanced laser techniques to create tightly bound ground-state molecules close to quantum degeneracy.

Related papers

From atoms to molecules (and back)

Simon L. Cornish

Atoms colliding in a magnetic field can form weakly bound states called Feshbach molecules. These states have now been used in combination with advanced laser techniques to create tightly bound ground-state molecules close to quantum degeneracy.

Physics•Sep 25, 2008•4 citations

Creation and manipulation of bound states in the continuum with lasers: Applications to cold atoms and molecules

Bimalendu Deb, G. S. Agarwal

It is possible to create and manipulate bound states in continuum in atom-atom cold collisions by lasers and a magnetic field, employing currently available techniques of photoaasociation and magnetic Feshbach resonance.

arXiv:1410.2950•Physical Review A•Dec 10, 2014•16 citations

From atoms to molecules

C. J. Pethick, H. Smith

A new facet was added to the study of dilute gases by the production and subsequent Bose–Einstein condensation of diatomic molecules from a gas of fermionic atoms. Feshbach resonances which, as we have seen in Sec. 5.4, make it possible to tune the atom–atom interaction, play a crucial role in the experiments. At the magnetic field strength for which the binding energy of the molecule vanishes, the inverse of the scattering length, which determines the low-energy effective interaction between atoms, passes through zero. In the experiments to produce molecules, one starts with a mixture of two species of fermion, most commonly different hyperfine states of the same isotope, in a magnetic field of such a strength that the molecular state has an energy higher than that of two zero-momentum atoms in the open channel. The magnetic field is then altered to a value at which the molecular state is bound with respect to two atoms in the open channel, and in this process, many of the atoms combine to form molecules. These molecules have binding energies in the 10 −9 eV range, and are thus extremely weakly bound by the standards of conventional molecular physics. In addition, they are very extended, with atomic separations as large as one micron. These molecules, being bosons, can undergo Bose–Einstein condensation, just as bosonic atoms do.

Cambridge University Press eBooks•Sep 11, 2008•0 citations

Exploring Few-body Scattering Resonances in a Bose-Fermi Mixture: From Feshbach Dimers to Efimov Trimers

Tyler D. Cumby

This thesis presents experiments exploring Feshbach molecules and Efimov trimers in an ultracold Bose-Fermi atomic gas mixture of 40K and 87Rb. These bound states are accessed via scattering resonances, called Fano-Feshbach resonances, which arise as a consequence of a bound state being tuned through degeneracy with the threshold energy of colliding atoms. In addition to allowing the tunability of interactions, the Fano-Feshbach resonance allows for a weakly bound molecule state, called the Feshbach molecule state, to be populated. The efficiency of conversion to the Feshbach molecule state depends upon the rate with which the bound state energy is swept through degeneracy with atomic threshold energy. In regions of large scattering lengths, three-body bound states, called Efimov states, also influence inelastic Bose-Bose-Fermi collisions and boson+molecule collisions in our system. The work presented in this thesis utilizes a magnetically tunable Fano-Feshbach resonance to study Feshbach molecule creation in the perturbative limit (the limit of fast magnetic-field sweeps) and the saturated limit (the limit of slow sweeps), where a phenomenological model is applied to understand the conversion efficiency as well as the quantum degeneracy of the molecules. In addition, I present a study of boson+molecule collision rates and Bose-Bose-Fermi collision rates in order to observe signatures of Efimov states and compare against results in the gas mixture 41K-87Rb to address the question of universality of the three-body parameter in heteronuclear gas mixtures.

•Jan 1, 2012•0 citations

Optimal molecule production from Bose condensed atoms using non-linear magnetic field sweeps through a Feshbach resonance

Jae‐Yoon Jeong, Christopher P. Search

Bulletin of the American Physical Society•May 19, 2006•0 citations

Dark state experiments with ultracold, deeply-bound triplet molecules

Florian Lang, Christoph Strauss, Klaus Winkler +3 more

We examine dark quantum superposition states of weakly bound Rb2 Feshbach molecules and tightly bound triplet Rb2 molecules in the rovibrational ground state, created by subjecting a pure sample of Feshbach molecules in an optical lattice to a bichromatic Raman laser field. We analyze, both experimentally and theoretically, the creation and dynamics of these dark states. Coherent wavepacket oscillations of deeply bound molecules in lattice sites, as previously observed by Lang et al. (Phys. Rev. Lett., 2008, 101, 133005), are suppressed due to laser-induced phase locking of molecular levels. This can be understood as the appearance of a novel multilevel dark state. In addition, the experimental methods developed help to determine important properties of our coupled atom/ laser system.

arXiv:0810.5744•Faraday Discussions•Jan 1, 2009•7 citations
A new facet was added to the study of dilute gases by the production and subsequent Bose–Einstein condensation of diatomic molecules from a gas of fermionic atoms. Feshbach resonances which, as we have seen in Sec. 5.4, make it possible to tune the atom–atom interaction, play a crucial role in the experiments. At the magnetic field strength for which the binding energy of the molecule vanishes, the inverse of the scattering length, which determines the low-energy effective interaction between atoms, passes through zero. In the experiments to produce molecules, one starts with a mixture of two species of fermion, most commonly different hyperfine states of the same isotope, in a magnetic field of such a strength that the molecular state has an energy higher than that of two zero-momentum atoms in the open channel. The magnetic field is then altered to a value at which the molecular state is bound with respect to two atoms in the open channel, and in this process, many of the atoms combine to form molecules. These molecules have binding energies in the 10 −9 eV range, and are thus extremely weakly bound by the standards of conventional molecular physics. In addition, they are very extended, with atomic separations as large as one micron. These molecules, being bosons, can undergo Bose–Einstein condensation, just as bosonic atoms do.
This thesis presents experiments exploring Feshbach molecules and Efimov trimers in an ultracold Bose-Fermi atomic gas mixture of 40K and 87Rb. These bound states are accessed via scattering resonances, called Fano-Feshbach resonances, which arise as a consequence of a bound state being tuned through degeneracy with the threshold energy of colliding atoms. In addition to allowing the tunability of interactions, the Fano-Feshbach resonance allows for a weakly bound molecule state, called the Feshbach molecule state, to be populated. The efficiency of conversion to the Feshbach molecule state depends upon the rate with which the bound state energy is swept through degeneracy with atomic threshold energy. In regions of large scattering lengths, three-body bound states, called Efimov states, also influence inelastic Bose-Bose-Fermi collisions and boson+molecule collisions in our system. The work presented in this thesis utilizes a magnetically tunable Fano-Feshbach resonance to study Feshbach molecule creation in the perturbative limit (the limit of fast magnetic-field sweeps) and the saturated limit (the limit of slow sweeps), where a phenomenological model is applied to understand the conversion efficiency as well as the quantum degeneracy of the molecules. In addition, I present a study of boson+molecule collision rates and Bose-Bose-Fermi collision rates in order to observe signatures of Efimov states and compare against results in the gas mixture 41K-87Rb to address the question of universality of the three-body parameter in heteronuclear gas mixtures.
We examine dark quantum superposition states of weakly bound Rb2 Feshbach molecules and tightly bound triplet Rb2 molecules in the rovibrational ground state, created by subjecting a pure sample of Feshbach molecules in an optical lattice to a bichromatic Raman laser field. We analyze, both experimentally and theoretically, the creation and dynamics of these dark states. Coherent wavepacket oscillations of deeply bound molecules in lattice sites, as previously observed by Lang et al. (Phys. Rev. Lett., 2008, 101, 133005), are suppressed due to laser-induced phase locking of molecular levels. This can be understood as the appearance of a novel multilevel dark state. In addition, the experimental methods developed help to determine important properties of our coupled atom/ laser system.