Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2011.12396 · Physical Review A

Cold-atom–dimer reaction rates with He4, Li6,7 , and Na23

M. A. Shalchi, Marcelo Takeshi Yamashita, T. Frederico, Lauro Tomio

Published Dec 17, 2020• 8 citations
arXivHTMLPDF

Abstract

Atom-dimer exchange and dissociation reaction rates are predicted for different combinations of two $^{4}\mathrm{He}$ atoms and one of the alkaline species among $^{6}\mathrm{Li}, ^{7}\mathrm{Li}$, and $^{23}\mathrm{Na}$, by using three-body scattering formalism with short-range two-body interactions. Our study was concerned with low-energy reaction rates in which the $s$-, $p$-, and $d$-wave contributions are the relevant ones. The $^{4}\mathrm{He}$ is chosen as one of the atoms in the binary mixture, in view of available previous investigations and laboratory accessibilities. Focusing on possible experimental cold-atom realizations with two-atomic mixtures, in which information on atom-dimer reaction rates can be extracted, we predict the occurrence of a dip in the elastic reaction rate for colliding energies smaller than 20 mK, when the dimer is the $^{4}\mathrm{He}^{23}\mathrm{Na}$ molecule. We are also anticipating a zero in the elastic $p$-wave contribution for the $^{4}\mathrm{He}+^{4}\mathrm{He}^{7}\mathrm{Li}$ and $^{4}\mathrm{He}+^{4}\mathrm{He}^{23}\mathrm{Na}$ reaction processes. With weakly bound molecules reacting with atoms at very low colliding energies, we interpret our results in the light of Efimov physics which supports model independence and robustness of our predictions. Specific sensitivities on the effective range were evidenced, highlighted by the particular inversion role of the $p$- and $d$-waves in the atom exchange and dissociation processes.

DOI
10.1103/physreva.102.062814

Related papers

Scattering of cold He4 on He4Li6,7 and He4Na23 molecules

M. A. Shalchi, A. Delfino, T. Frederico +1 more

We predict $s$-wave elastic cross-sections $\ensuremath{\sigma}$ for low-energy atom-molecule collisions with kinetic energies up to 40 mK for the $^{4}\mathrm{He}$ collision with weakly bound diatomic molecules formed by $^{4}\mathrm{He}$ with $^{7}\mathrm{Li},\phantom{\rule{0.28em}{0ex}}^{6}\mathrm{Li}$, and $^{23}\mathrm{Na}$. Our scattering calculations are performed by using diatomic and triatomic molecular binding energies obtained from several available realistic models as input in a renormalized zero-range model as well as a finite-range one-term separable potential in order to quantify the relevance of range corrections to our predictions. Of particular relevance for possible experimental realization, we show the occurrence of a zero in $\ensuremath{\sigma}$ for the collision of cold $^{4}\mathrm{He}$ on a $^{4}\mathrm{He}\phantom{\rule{0.16em}{0ex}}^{23}\mathrm{Na}$ molecule below 20 mK. Also our results for the elastic collision $^{4}\mathrm{He}$ on $^{4}\mathrm{He}\phantom{\rule{0.16em}{0ex}}^{6,7}\mathrm{Li}$ molecules suggest that $\ensuremath{\sigma}$ varies considerably for the realistic models studied. As the chosen molecules are weakly bound and the scattering energies are very low, our results are interpreted on the light of the Efimov physics, which explains the model independence and robustness of our predictions despite some sensitivity on the potential range.

arXiv:1809.09140•Physical Review A•Sep 24, 2018•4 citations

Prediction of a weakly bound excited state in the He24–7Li molecule

A. Delfino, T. Frederico, Lauro Tomio

A scale-independent approach, valid for weakly bound three-body systems, is used to analyze the existence of excited Thomas–Efimov states in molecular systems with three atoms: a helium dimer together with isotopes of lithium (Li6 and Li7) and sodium (Na23). With the present study and the available data, we can clearly predict that the He24−Li7 system supports an excited state with binding energy close to 2.31 mK.

The Journal of Chemical Physics•Nov 8, 2000•31 citations

Collisional properties of weakly bound heteronuclear dimers

Bout Marcelis, S. J. J. M. F. Kokkelmans, Georgy V. Shlyapnikov +1 more

We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a two-species mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimer-dimer repulsion originating from the exchange of the light atoms. In order to solve the dimer-dimer scattering problem we develop a theoretical approach, which provides a physically transparent and quantitative description of this four-atom system in terms of three- and two-body observables. We calculate the elastic scattering amplitude and the rates of inelastic processes such as the trimer formation and the relaxation of dimers into deeply bound molecular states. Irrespective of whether the heavy atoms are bosons or fermions, the inelastic rate can be significantly lower than the rate of elastic collisions. Moreover, the measurement of the inelastic rate which is a four-body observable, can be an efficient and precise tool for determining three-body observables such as the three-body parameter, positions of Efimov states, and their lifetimes.

arXiv:0711.4632•Physical Review A•Mar 13, 2008•47 citations

Interactions and collisions of cold molecules: lithium + lithium dimer

Marko T. Cvitaš

There is at present great interest in the properties of ultracold molecules. Molecules are created in traps in excited rovibrational states and any vibrational relaxation results in the trap loss. This thesis provides a theoretical study of interactions and collisions in the spin-polarized lithium -b lithium dimer system at ultralow energies. Potential energy surface of the electronic quartet ground state of lithium trimer is generated ab initio using the CCSD(T) method and represented by an IMLS/Shepard fit. Long-range nonadditive interactions are modelled using a symmetric global form with coefficients taken from a fit to the atom-molecule dispersion coefficients. The surface allows barrierless atom-exchange reactions. It has a global minimum of ≈ 4000 cm(^-1) at equilateral geometries with r(_e) = 3.1 Å. The nonadditive interactions are very strong near equilibrium. They increase the well depth by a factor of 4 and reduce the interatomic distance by ≈ 1 Å. Another surface of À symmetry in C(_s) meets the ground state surface at linear geometries at short range. Part of the seam, near D(_ooh) geometries, is in an energetically accessible region for cold collisions. Inside the seam, the lowest À surface correlates with (^4)II rather than (^4)Σ state. Inelastic and reactive collisions are investigated using a quantum mechanical coupled channel method in hyperspherical coordinates. Bosonic and fermionic systems in the spin-stretched states are considered. The inelastic rate coefficients from the rovibrationally excited states of dimer at ultralow collision energies are large, often above 10-(^-10) cm(^3)s(^-1) The elastic cross sections are ≈ 3 orders of magnitude lower at 1 nK. Atom-molecule mixtures, at the densities found in Bose-Einstein condensates of alkali metal atoms that were recently produced, would last only a fraction of a second. Classical Langevin model describes semi-quantitatively the energy dependence of inelastic cross sections above ≈ 50 mK. No systematic differences between the bosonic and fermionic systems were found. Sensitivity of the results on potential was investigated. Reactions in isotopic mixtures of lithium may be exothermic even from the molecular ground state. The reactive rate coefficients are 1 - 2 orders of magnitude smaller than those in systems involving an initially vibrationally excited dimer.

•Jan 1, 2004•0 citations

Atom-Dimer Scattering in a Three-Component Fermi Gas

Thomas Lompe, T. B. Ottenstein, Friedhelm Serwane +4 more

Ultracold gases of three distinguishable particles with large scattering lengths are expected to show rich few-body physics related to the Efimov effect. We have created three different mixtures of ultracold 6Li atoms and weakly bound 6Li2 dimers consisting of atoms in three different hyperfine states and studied their inelastic decay via atom-dimer collisions. We have found resonant enhancement of the decay due to the crossing of Efimov-like trimer states with the atom-dimer continuum in one mixture as well as minima of the decay in another mixture, which we interpret as a suppression of exchange reactions of the type |12+|3→|23+|1. Such a suppression is caused by interference between different decay paths and demonstrates the possibility of using Efimov physics to control the rate constants for molecular exchange reactions in the ultracold regime.

arXiv:1003.0600•Physical Review Letters•Sep 2, 2010•101 citations

Elastic and exchanged atom–molecule collisions in 4He–4He–X (X = 40K, 85Rb, 133Cs) systems at low energy

Huan Zhu, Ningning Gao, Hui-Li Han

We investigate the low-energy collision properties of the 4He-4He-X (X = 40K, 85Rb, 133Cs) systems using the R-matrix propagation method within the hyperspherical coordinate framework. The atom-dimer scattering length and atom-molecule collisional exchange rates are derived by solving the three-body Schrödinger equation using a potential energy surface obtained by summing three realistic pairwise potentials. Our results show that the atom-molecule collision exchange rates in the 4He2 + X → 4HeX + 4He process are primarily governed by the 4HeX two-body scattering lengths. Furthermore, when scaled by this parameter, the inelastic cross sections for all three systems collapse onto a single curve, demonstrating universal behavior. These findings provide new insights into the fundamental properties of weakly bound helium-helium-alkali-metal systems and their role in low-energy three-body collisions.

The Journal of Chemical Physics•May 1, 2025•0 citations
Atom-dimer exchange and dissociation reaction rates are predicted for different combinations of two 4He^{4}\mathrm{He}4He atoms and one of the alkaline species among 6Li,7Li^{6}\mathrm{Li}, ^{7}\mathrm{Li}6Li,7Li, and 23Na^{23}\mathrm{Na}23Na, by using three-body scattering formalism with short-range two-body interactions. Our study was concerned with low-energy reaction rates in which the sss-, ppp-, and ddd-wave contributions are the relevant ones. The 4He^{4}\mathrm{He}4He is chosen as one of the atoms in the binary mixture, in view of available previous investigations and laboratory accessibilities. Focusing on possible experimental cold-atom realizations with two-atomic mixtures, in which information on atom-dimer reaction rates can be extracted, we predict the occurrence of a dip in the elastic reaction rate for colliding energies smaller than 20 mK, when the dimer is the 4He23Na^{4}\mathrm{He}^{23}\mathrm{Na}4He23Na molecule. We are also anticipating a zero in the elastic ppp-wave contribution for the 4He+4He7Li^{4}\mathrm{He}+^{4}\mathrm{He}^{7}\mathrm{Li}4He+4He7Li and 4He+4He23Na^{4}\mathrm{He}+^{4}\mathrm{He}^{23}\mathrm{Na}4He+4He23Na reaction processes. With weakly bound molecules reacting with atoms at very low colliding energies, we interpret our results in the light of Efimov physics which supports model independence and robustness of our predictions. Specific sensitivities on the effective range were evidenced, highlighted by the particular inversion role of the ppp- and ddd-waves in the atom exchange and dissociation processes.
We predict sss-wave elastic cross-sections $\ensuremath{\sigma}$ for low-energy atom-molecule collisions with kinetic energies up to 40 mK for the 4He^{4}\mathrm{He}4He collision with weakly bound diatomic molecules formed by 4He^{4}\mathrm{He}4He with 7Li,6Li^{7}\mathrm{Li},\phantom{\rule{0.28em}{0ex}}^{6}\mathrm{Li}7Li,6Li, and 23Na^{23}\mathrm{Na}23Na. Our scattering calculations are performed by using diatomic and triatomic molecular binding energies obtained from several available realistic models as input in a renormalized zero-range model as well as a finite-range one-term separable potential in order to quantify the relevance of range corrections to our predictions. Of particular relevance for possible experimental realization, we show the occurrence of a zero in $\ensuremath{\sigma}$ for the collision of cold 4He^{4}\mathrm{He}4He on a 4He23Na^{4}\mathrm{He}\phantom{\rule{0.16em}{0ex}}^{23}\mathrm{Na}4He23Na molecule below 20 mK. Also our results for the elastic collision 4He^{4}\mathrm{He}4He on 4He6,7Li^{4}\mathrm{He}\phantom{\rule{0.16em}{0ex}}^{6,7}\mathrm{Li}4He6,7Li molecules suggest that $\ensuremath{\sigma}$ varies considerably for the realistic models studied. As the chosen molecules are weakly bound and the scattering energies are very low, our results are interpreted on the light of the Efimov physics, which explains the model independence and robustness of our predictions despite some sensitivity on the potential range.
We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a two-species mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimer-dimer repulsion originating from the exchange of the light atoms. In order to solve the dimer-dimer scattering problem we develop a theoretical approach, which provides a physically transparent and quantitative description of this four-atom system in terms of three- and two-body observables. We calculate the elastic scattering amplitude and the rates of inelastic processes such as the trimer formation and the relaxation of dimers into deeply bound molecular states. Irrespective of whether the heavy atoms are bosons or fermions, the inelastic rate can be significantly lower than the rate of elastic collisions. Moreover, the measurement of the inelastic rate which is a four-body observable, can be an efficient and precise tool for determining three-body observables such as the three-body parameter, positions of Efimov states, and their lifetimes.
There is at present great interest in the properties of ultracold molecules. Molecules are created in traps in excited rovibrational states and any vibrational relaxation results in the trap loss. This thesis provides a theoretical study of interactions and collisions in the spin-polarized lithium -b lithium dimer system at ultralow energies. Potential energy surface of the electronic quartet ground state of lithium trimer is generated ab initio using the CCSD(T) method and represented by an IMLS/Shepard fit. Long-range nonadditive interactions are modelled using a symmetric global form with coefficients taken from a fit to the atom-molecule dispersion coefficients. The surface allows barrierless atom-exchange reactions. It has a global minimum of ≈ 4000 cm(^-1) at equilateral geometries with r(_e) = 3.1 Å. The nonadditive interactions are very strong near equilibrium. They increase the well depth by a factor of 4 and reduce the interatomic distance by ≈ 1 Å. Another surface of À symmetry in C(_s) meets the ground state surface at linear geometries at short range. Part of the seam, near D(_ooh) geometries, is in an energetically accessible region for cold collisions. Inside the seam, the lowest À surface correlates with (^4)II rather than (^4)Σ state. Inelastic and reactive collisions are investigated using a quantum mechanical coupled channel method in hyperspherical coordinates. Bosonic and fermionic systems in the spin-stretched states are considered. The inelastic rate coefficients from the rovibrationally excited states of dimer at ultralow collision energies are large, often above 10-(^-10) cm(^3)s(^-1) The elastic cross sections are ≈ 3 orders of magnitude lower at 1 nK. Atom-molecule mixtures, at the densities found in Bose-Einstein condensates of alkali metal atoms that were recently produced, would last only a fraction of a second. Classical Langevin model describes semi-quantitatively the energy dependence of inelastic cross sections above ≈ 50 mK. No systematic differences between the bosonic and fermionic systems were found. Sensitivity of the results on potential was investigated. Reactions in isotopic mixtures of lithium may be exothermic even from the molecular ground state. The reactive rate coefficients are 1 - 2 orders of magnitude smaller than those in systems involving an initially vibrationally excited dimer.
Ultracold gases of three distinguishable particles with large scattering lengths are expected to show rich few-body physics related to the Efimov effect. We have created three different mixtures of ultracold 6Li atoms and weakly bound 6Li2 dimers consisting of atoms in three different hyperfine states and studied their inelastic decay via atom-dimer collisions. We have found resonant enhancement of the decay due to the crossing of Efimov-like trimer states with the atom-dimer continuum in one mixture as well as minima of the decay in another mixture, which we interpret as a suppression of exchange reactions of the type |12+|3→|23+|1. Such a suppression is caused by interference between different decay paths and demonstrates the possibility of using Efimov physics to control the rate constants for molecular exchange reactions in the ultracold regime.
We investigate the low-energy collision properties of the 4He-4He-X (X = 40K, 85Rb, 133Cs) systems using the R-matrix propagation method within the hyperspherical coordinate framework. The atom-dimer scattering length and atom-molecule collisional exchange rates are derived by solving the three-body Schrödinger equation using a potential energy surface obtained by summing three realistic pairwise potentials. Our results show that the atom-molecule collision exchange rates in the 4He2 + X → 4HeX + 4He process are primarily governed by the 4HeX two-body scattering lengths. Furthermore, when scaled by this parameter, the inelastic cross sections for all three systems collapse onto a single curve, demonstrating universal behavior. These findings provide new insights into the fundamental properties of weakly bound helium-helium-alkali-metal systems and their role in low-energy three-body collisions.