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 relaxation is 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. Finally, we discuss the possibilities for spectroscopic detection of these complexes, including a calculation of expected spectra for Ag(3)He, and report on our spectroscopic search for Ag(3)He, which produced a null result.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 relaxation is 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. Finally, we discuss the possibilities for spectroscopic detection of these complexes, including a calculation of expected spectra for Ag(3)He, and report on our spectroscopic search for Ag(3)He, which produced a null result.

arXiv:1104.4973Physical Chemistry Chemical PhysicsJan 1, 201131 citations

Suppression of Molecular Decay in Ultracold Gases without Fermi Statistics

José Paulo D'Incao, Brett D. Esry

We study inelastic processes for ultracold three-body systems in which only one interaction is resonant. We show that at ultracold temperatures three-body recombination in such systems leads mainly to the formation of weakly bound molecules. In addition, and perhaps more importantly, we have found that the decay rates for weakly bound molecules due to collisions with other atoms can be suppressed not only without fermionic statistics but also when bosonic statistics applies. These results indicate that recombination in three-component atomic gases can be used as an efficient mechanism for molecular formation, allowing the achievement of high molecular densities.We study inelastic processes for ultracold three-body systems in which only one interaction is resonant. We show that at ultracold temperatures three-body recombination in such systems leads mainly to the formation of weakly bound molecules. In addition, and perhaps more importantly, we have found that the decay rates for weakly bound molecules due to collisions with other atoms can be suppressed not only without fermionic statistics but also when bosonic statistics applies. These results indicate that recombination in three-component atomic gases can be used as an efficient mechanism for molecular formation, allowing the achievement of high molecular densities.

arXiv:0711.3238Physical Review LettersApr 25, 200827 citations

On the Existence of Molecular Bound States for 3He and 4He

Richard David Etters, J. C. Raich, Prakash Chand

The Journal of Chemical PhysicsNov 15, 197111 citations

Formation and detection of ultracold ground-state polar molecules

Christopher Haimberger, Jan Kleinert, Mishkatul Bhattacharya +1 more

We report on the formation of translationally cold $\mathrm{NaCs}$ molecules starting from a laser-cooled atomic vapor of $\mathrm{Na}$ and $\mathrm{Cs}$ atoms. Colliding atoms are transferred into bound molecular states in a two-step photoactivated process in which the atoms are first photoassociated by trap photons into an excited state molecular complex and then allowed to decay into a bound molecular ground state. Time-of-flight measurements show a translational temperature $T=260\ifmmode\pm\else\textpm\fi{}130\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ that reflects the measured temperature of the initial atomic gas.We report on the formation of translationally cold $\mathrm{NaCs}$ molecules starting from a laser-cooled atomic vapor of $\mathrm{Na}$ and $\mathrm{Cs}$ atoms. Colliding atoms are transferred into bound molecular states in a two-step photoactivated process in which the atoms are first photoassociated by trap photons into an excited state molecular complex and then allowed to decay into a bound molecular ground state. Time-of-flight measurements show a translational temperature $T=260\ifmmode\pm\else\textpm\fi{}130\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ that reflects the measured temperature of the initial atomic gas.

Physical Review AAug 27, 2004159 citations

Weakly Bound Li He $_\mathbf{2 }$ 2 MoleculesWeakly Bound Li He $$_\mathbf{2 }$$ 2 Molecules

Elena A. Kolganova

arXiv:1612.03820Few-Body SystemsJan 24, 201711 citations

Formation of weakly bound molecular complexes: (

^3

3 He)

_2

We report on the formation of translationally cold

\mathrm{NaCs}

molecules starting from a laser-cooled atomic vapor of

\mathrm{Na}

and

\mathrm{Cs}

atoms. Colliding atoms are transferred into bound molecular states in a two-step photoactivated process in which the atoms are first photoassociated by trap photons into an excited state molecular complex and then allowed to decay into a bound molecular ground state. Time-of-flight measurements show a translational temperature $T=260\ifmmode\pm\else\textpm\fi{}130\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ that reflects the measured temperature of the initial atomic gas.

Weakly Bound Li He

_\mathbf{2 }

2 Molecules