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

Physical Review A

Nonadiabatic collisions of CaH with Li: Importance of spin-orbit-induced spin relaxation in spin-polarized sympathetic cooling of CaH

Mick Warehime, Jacek A. Kłos

Published Sep 8, 2015• 9 citations
Publisher

Abstract

We apply our recently developed, quantum, nonadiabatic, two-dimensional finite element method [Warehime et al., J. Chem. Phys. 142, 034108 (2015).] to estimate the probability of the nonadiabatic reaction in spin-polarized $\mathrm{Li}{(}^{2}S)+\mathrm{CaH}{(}^{2}{\mathrm{\ensuremath{\Sigma}}}^{+})$. This spin-orbit-induced reaction leads to trap loss due to the opening of a barrierless pathway to the $\mathrm{Ca}{(}^{1}S)+\mathrm{LiH}{(}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+})$ products. To investigate this reaction we calculate three two-dimensional radial cuts of the potential energy surfaces for the triplet and singlet electronic states. We also calculate the spin-orbit coupling matrix element between these two electronic states. From our nonadiabatic scattering calculations we estimate the spin-flip probability in the sympathetic cooling of the CaH molecule with ultracold Li atoms to be small: on the order of ${10}^{\ensuremath{-}7}$ and increasing to ${10}^{\ensuremath{-}4}$ at higher temperatures. We estimate the order of the rate constant in our reduced dimensionality approach for the reaction proceeding on the singlet potential at a temperature of 1 K to be ${10}^{\ensuremath{-}10}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{3}$/s. This is of the same order as the measured value of $3.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{3}/s$ [Singh et al., Phys. Rev. Lett. 108, 203201 (2012)]. This reaction rate is at least seven orders of magnitude larger than our estimated rate of the spin-orbit-induced triplet to singlet reaction. Our nonadiabatic result is encouraging for the experimental prospects for this title system.

DOI
10.1103/physreva.92.032703

Related papers

Cold collisions of heavy Σ2 molecules with alkali-metal atoms in a magnetic field: Ab initio analysis and prospects for sympathetic cooling of SrOH(Σ+2) by Li(S2)

Masato Morita, Jacek A. Kłos, Alexei A. Buchachenko +1 more

We use accurate ab initio and quantum scattering calculations to explore the prospects for sympathetic cooling of the heavy molecular radical $\mathrm{SrOH}{(}^{2}{\mathrm{\ensuremath{\Sigma}}}^{+})$ by ultracold Li atoms in a magnetic trap. Our ab initio calculations show that the chemical reaction between spin-polarized Li and SrOH, which occurs on the triplet Li-SrOH potential energy surface (PES), is strongly endothermic and hence energetically forbidden at ultralow temperatures. The chemical reaction $\mathrm{Li}(^{2}S)+\mathrm{SrOH}{(}^{2}{\mathrm{\ensuremath{\Sigma}}}^{+})\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\mathrm{Sr}(^{1}S)+\mathrm{LiOH}{(}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+})$ occurs barrierlessly on the singlet PES and is exothermic by 2505 ${\mathrm{cm}}^{\ensuremath{-}1}$. A two-dimensional PES for the triplet electronic state of Li-SrOH is calculated ab initio using the partially spin-restricted coupled cluster method with single, double, and perturbative triple excitations and a large correlation-consistent basis set. The highly anisotropic PES has a deep global minimum in the skewed Li-HOSr geometry with ${D}_{e}=4932\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and saddle points in collinear configurations. Our quantum scattering calculations predict low spin-relaxation rates in fully spin-polarized Li + SrOH collisions with the ratios of elastic to inelastic collision rates well in excess of 100 over a wide range of magnetic fields (1--1000 G) and collision energies (${10}^{\ensuremath{-}5}$ to 0.1 K), suggesting favorable prospects for sympathetic cooling of SrOH molecules with spin-polarized Li atoms in a magnetic trap. We find that spin relaxation in Li + SrOH collisions occurs via a direct mechanism mediated by the magnetic dipole-dipole interaction between the electron spins of Li and SrOH, and that the indirect (spin-rotation) mechanism is strongly suppressed. The upper limit to the Li + SrOH reaction rate coefficient calculated for the singlet PES using adiabatic capture theory is found to decrease from $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{3}$/s to a limiting value of $3.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{3}$/s with decreasing temperature from 0.1 K to 1 $\ensuremath{\mu}\mathrm{K}$.

arXiv:1702.05856•Physical Review A•Jun 26, 2017•22 citations

Ultracold spin-polarized mixtures of 2Σ molecules with S -state atoms: Collisional stability and implications for sympathetic cooling

Timur V. Tscherbul, Jacek A. Kłos, Alexei A. Buchachenko

The prospects of sympathetic cooling of polar molecules with magnetically cotrapped alkali-metal atoms are generally considered poor due to strongly anisotropic atom-molecule interactions leading to large spin relaxation rates. Using rigorous quantum scattering calculations based on ab initio interaction potentials, we show that inelastic spin relaxation in low-temperature collisions of CaH(${}^{2}\ensuremath{\Sigma}$) molecules with Li and Mg atoms occurs at a slow rate despite the strongly anisotropic interactions. This unexpected result, which we rationalize using multichannel quantum-defect theory, opens up the possibility of sympathetic cooling of polar ${}^{2}\ensuremath{\Sigma}$ molecules with alkali-metal atoms in a magnetic trap and with alkaline-earth-metal atoms in an optical dipole trap.

arXiv:1106.1492•Physical Review A•Oct 28, 2011•49 citations

Sympathetic cooling of the Ba + ion by collisions with ultracold Rb atoms: Theoretical prospects

Michał Krych, Wojciech Skomorowski, Filip Pawłowski +2 more

State-of-the-art ab initio techniques have been applied to compute the potential energy curves of the (BaRb)${}^{+}$ molecular ion in the Born-Oppenheimer approximation for the singlet and triplet states dissociating into the ground-state ${}^{1}$$S$ Rb${}^{+}$ ion and the Ba atom in the ground ${}^{1}$$S$ state or the lowest singlet or triplet $d$ excited states, and for the singlet and triplet states dissociating into the ground-state ${}^{2}$$S$ Rb atom and the ground-state ${}^{2}$$S$ Ba${}^{+}$ ion. The ground-state potential energy was obtained with the coupled-cluster method restricted to single, double, and nonperturbative triple excitations. The first triplet states in the $\ensuremath{\Sigma}$, $\ensuremath{\Pi}$, and $\ensuremath{\Delta}$ symmetries were computed with the restricted open-shell coupled-cluster method restricted to single, double, and nonperturbative triple excitations. All other excited-state potential energy curves were computed using the equation of motion approach within the coupled-cluster singles, doubles, and linear triples framework. The long-range coefficients describing the electrostatic, induction, and dispersion interactions at large interatomic distances are also reported. The electric transition dipole moments governing the $x$ ${}^{1}\ensuremath{\Sigma}\ensuremath{\rightarrow}{}^{1}\ensuremath{\Sigma},{}^{1}\ensuremath{\Pi}$ transitions have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Nonadiabatic radial and angular coupling matrix elements as well as the spin-orbit coupling matrix elements have been evaluated using the multireference configuration-interaction method restricted to single and double excitations with a large active space. With these couplings, the spin-orbit-coupled (relativistic) potential energy curves for the 0${}^{+}$ and 1 states relevant for the running experiments have been obtained. Finally, relativistic transition moments and nonadiabatic coupling matrix elements were obtained from the nonrelativistic results and spin-orbit eigenvectors. The electronic structure input has been employed in the single-channel scattering calculations of the collisional cross sections between the Ba${}^{+}$ ion and Rb atom. Both nonrelativistic and relativistic potentials were used in these calculations. Our results show that the inelastic cross section corresponding to the charge transfer from the Rb atom to the Ba${}^{+}$ ion is much smaller than the elastic one over a wide range of energies up to 1 mK. This suggests that sympathetic cooling of the Ba${}^{+}$ ion by collisions with ultracold Rb atoms should be possible.

arXiv:1008.0840•Physical Review A•Mar 31, 2011•60 citations

Signatures of Non-universal Quantum Dynamics of Ultracold Chemical Reactions of Polar Alkali Dimer Molecules with Alkali Metal Atoms: Li(2S) + NaLi(a3Σ+) → Na(2S) + Li2(a3Σu+)

Masato Morita, Brian K. Kendrick, Jacek A. Kłos +3 more

Ultracold chemical reactions of weakly bound triplet-state alkali metal dimer molecules have recently attracted much experimental interest. We perform rigorous quantum scattering calculations with a new ab initio potential energy surface to explore the chemical reaction of spin-polarized NaLi( a 3 Σ + ) and Li( 2 S) to form Li 2 ( a 3 Σ u + ) and Na( 2 S). The reaction is exothermic and proceeds readily at ultralow temperatures. Significantly, we observe strong sensitivity of the total reaction rate to small variations of the three-body part of the Li 2 Na interaction at short range, which we attribute to a relatively small number of open Li 2 ( a 3 Σ u + ) product channels populated in the reaction. This provides the first signature of highly non-universal dynamics seen in rigorous quantum reactive scattering calculations of an ultracold exothermic insertion reaction involving a polar alkali dimer molecule, opening up the possibility of probing microscopic interactions in atom+molecule collision complexes via ultracold reactive scattering experiments.

arXiv:2301.08208•The Journal of Physical Chemistry Letters•Mar 31, 2023•12 citations

The Li + CaF → Ca + LiF chemical reaction under cold conditions

Humberto da Silva, Qian Yao, Masato Morita +3 more

electronic structure and full-dimensional quantum dynamical calculations of the Li + CaF → LiF + Ca chemical reaction. The electronic structure calculations are performed using the internally contracted multi-reference configuration-interaction method with Davidson correction (MRCI + Q). An analytic fit of the interaction energies is obtained using a many-body expansion method. A coupled-channel quantum reactive scattering approach implemented in hyperspherical coordinates is adopted for the scattering calculations under cold conditions. Results show that the Li + CaF reaction populates several low-lying vibrational levels and many rotational levels of the product LiF molecule and that the reaction is inefficient in the 1-100 mK regime allowing sympathetic cooling of CaF by collisions with cold Li atoms.

arXiv:2304.12927•Physical Chemistry Chemical Physics•Jan 1, 2023•3 citations

Interactions and dynamics in Li+Li2 ultracold collisions

Marko T. Cvitaš, Pavel Soldán, Jeremy M. Hutson +2 more

A potential energy surface for the lowest quartet electronic state ((4)A(')) of lithium trimer is developed and used to study spin-polarized Li+Li(2) collisions at ultralow kinetic energies. The potential energy surface allows barrierless atom exchange reactions. Elastic and inelastic cross sections are calculated for collisions involving a variety of rovibrational states of Li(2). Inelastic collisions are responsible for trap loss in molecule production experiments. Isotope effects and the sensitivity of the results to details of the potential energy surface are investigated. It is found that for vibrationally excited states, the cross sections are only quite weakly dependent on details of the potential energy surface.

arXiv:physics/0703136•The Journal of Chemical Physics•Aug 20, 2007•71 citations
We apply our recently developed, quantum, nonadiabatic, two-dimensional finite element method [Warehime et al., J. Chem. Phys. 142, 034108 (2015).] to estimate the probability of the nonadiabatic reaction in spin-polarized Li(2S)+CaH(2\ensuremathΣ+)\mathrm{Li}{(}^{2}S)+\mathrm{CaH}{(}^{2}{\mathrm{\ensuremath{\Sigma}}}^{+})Li(2S)+CaH(2\ensuremathΣ+). This spin-orbit-induced reaction leads to trap loss due to the opening of a barrierless pathway to the Ca(1S)+LiH(1\ensuremathΣ+)\mathrm{Ca}{(}^{1}S)+\mathrm{LiH}{(}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+})Ca(1S)+LiH(1\ensuremathΣ+) products. To investigate this reaction we calculate three two-dimensional radial cuts of the potential energy surfaces for the triplet and singlet electronic states. We also calculate the spin-orbit coupling matrix element between these two electronic states. From our nonadiabatic scattering calculations we estimate the spin-flip probability in the sympathetic cooling of the CaH molecule with ultracold Li atoms to be small: on the order of 10\ensuremath−7{10}^{\ensuremath{-}7}10\ensuremath−7 and increasing to 10\ensuremath−4{10}^{\ensuremath{-}4}10\ensuremath−4 at higher temperatures. We estimate the order of the rate constant in our reduced dimensionality approach for the reaction proceeding on the singlet potential at a temperature of 1 K to be 10\ensuremath−10cm3{10}^{\ensuremath{-}10}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{3}10\ensuremath−10cm3/s. This is of the same order as the measured value of 3.6\ifmmode×\else\texttimes\fi10\ensuremath−10cm3/s3.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{3}/s3.6\ifmmode×\else\texttimes\fi10\ensuremath−10cm3/s [Singh et al., Phys. Rev. Lett. 108, 203201 (2012)]. This reaction rate is at least seven orders of magnitude larger than our estimated rate of the spin-orbit-induced triplet to singlet reaction. Our nonadiabatic result is encouraging for the experimental prospects for this title system.
We use accurate ab initio and quantum scattering calculations to explore the prospects for sympathetic cooling of the heavy molecular radical $\mathrm{SrOH}{(}^{2}{\mathrm{\ensuremath{\Sigma}}}^{+})$ by ultracold Li atoms in a magnetic trap. Our ab initio calculations show that the chemical reaction between spin-polarized Li and SrOH, which occurs on the triplet Li-SrOH potential energy surface (PES), is strongly endothermic and hence energetically forbidden at ultralow temperatures. The chemical reaction $\mathrm{Li}(^{2}S)+\mathrm{SrOH}{(}^{2}{\mathrm{\ensuremath{\Sigma}}}^{+})\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}\mathrm{Sr}(^{1}S)+\mathrm{LiOH}{(}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+})$ occurs barrierlessly on the singlet PES and is exothermic by 2505 ${\mathrm{cm}}^{\ensuremath{-}1}$. A two-dimensional PES for the triplet electronic state of Li-SrOH is calculated ab initio using the partially spin-restricted coupled cluster method with single, double, and perturbative triple excitations and a large correlation-consistent basis set. The highly anisotropic PES has a deep global minimum in the skewed Li-HOSr geometry with ${D}_{e}=4932\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and saddle points in collinear configurations. Our quantum scattering calculations predict low spin-relaxation rates in fully spin-polarized Li + SrOH collisions with the ratios of elastic to inelastic collision rates well in excess of 100 over a wide range of magnetic fields (1--1000 G) and collision energies (${10}^{\ensuremath{-}5}$ to 0.1 K), suggesting favorable prospects for sympathetic cooling of SrOH molecules with spin-polarized Li atoms in a magnetic trap. We find that spin relaxation in Li + SrOH collisions occurs via a direct mechanism mediated by the magnetic dipole-dipole interaction between the electron spins of Li and SrOH, and that the indirect (spin-rotation) mechanism is strongly suppressed. The upper limit to the Li + SrOH reaction rate coefficient calculated for the singlet PES using adiabatic capture theory is found to decrease from $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{3}$/s to a limiting value of $3.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{3}$/s with decreasing temperature from 0.1 K to 1 $\ensuremath{\mu}\mathrm{K}$.
The prospects of sympathetic cooling of polar molecules with magnetically cotrapped alkali-metal atoms are generally considered poor due to strongly anisotropic atom-molecule interactions leading to large spin relaxation rates. Using rigorous quantum scattering calculations based on ab initio interaction potentials, we show that inelastic spin relaxation in low-temperature collisions of CaH(${}^{2}\ensuremath{\Sigma}$) molecules with Li and Mg atoms occurs at a slow rate despite the strongly anisotropic interactions. This unexpected result, which we rationalize using multichannel quantum-defect theory, opens up the possibility of sympathetic cooling of polar ${}^{2}\ensuremath{\Sigma}$ molecules with alkali-metal atoms in a magnetic trap and with alkaline-earth-metal atoms in an optical dipole trap.
State-of-the-art ab initio techniques have been applied to compute the potential energy curves of the (BaRb)+{}^{+}+ molecular ion in the Born-Oppenheimer approximation for the singlet and triplet states dissociating into the ground-state 1{}^{1}1SSS Rb+{}^{+}+ ion and the Ba atom in the ground 1{}^{1}1SSS state or the lowest singlet or triplet ddd excited states, and for the singlet and triplet states dissociating into the ground-state 2{}^{2}2SSS Rb atom and the ground-state 2{}^{2}2SSS Ba+{}^{+}+ ion. The ground-state potential energy was obtained with the coupled-cluster method restricted to single, double, and nonperturbative triple excitations. The first triplet states in the $\ensuremath{\Sigma}$, $\ensuremath{\Pi}$, and $\ensuremath{\Delta}$ symmetries were computed with the restricted open-shell coupled-cluster method restricted to single, double, and nonperturbative triple excitations. All other excited-state potential energy curves were computed using the equation of motion approach within the coupled-cluster singles, doubles, and linear triples framework. The long-range coefficients describing the electrostatic, induction, and dispersion interactions at large interatomic distances are also reported. The electric transition dipole moments governing the xxx ${}^{1}\ensuremath{\Sigma}\ensuremath{\rightarrow}{}^{1}\ensuremath{\Sigma},{}^{1}\ensuremath{\Pi}$ transitions have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Nonadiabatic radial and angular coupling matrix elements as well as the spin-orbit coupling matrix elements have been evaluated using the multireference configuration-interaction method restricted to single and double excitations with a large active space. With these couplings, the spin-orbit-coupled (relativistic) potential energy curves for the 0+{}^{+}+ and 1 states relevant for the running experiments have been obtained. Finally, relativistic transition moments and nonadiabatic coupling matrix elements were obtained from the nonrelativistic results and spin-orbit eigenvectors. The electronic structure input has been employed in the single-channel scattering calculations of the collisional cross sections between the Ba+{}^{+}+ ion and Rb atom. Both nonrelativistic and relativistic potentials were used in these calculations. Our results show that the inelastic cross section corresponding to the charge transfer from the Rb atom to the Ba+{}^{+}+ ion is much smaller than the elastic one over a wide range of energies up to 1 mK. This suggests that sympathetic cooling of the Ba+{}^{+}+ ion by collisions with ultracold Rb atoms should be possible.
Ultracold chemical reactions of weakly bound triplet-state alkali metal dimer molecules have recently attracted much experimental interest. We perform rigorous quantum scattering calculations with a new ab initio potential energy surface to explore the chemical reaction of spin-polarized NaLi( a 3 Σ + ) and Li( 2 S) to form Li 2 ( a 3 Σ u + ) and Na( 2 S). The reaction is exothermic and proceeds readily at ultralow temperatures. Significantly, we observe strong sensitivity of the total reaction rate to small variations of the three-body part of the Li 2 Na interaction at short range, which we attribute to a relatively small number of open Li 2 ( a 3 Σ u + ) product channels populated in the reaction. This provides the first signature of highly non-universal dynamics seen in rigorous quantum reactive scattering calculations of an ultracold exothermic insertion reaction involving a polar alkali dimer molecule, opening up the possibility of probing microscopic interactions in atom+molecule collision complexes via ultracold reactive scattering experiments.
electronic structure and full-dimensional quantum dynamical calculations of the Li + CaF → LiF + Ca chemical reaction. The electronic structure calculations are performed using the internally contracted multi-reference configuration-interaction method with Davidson correction (MRCI + Q). An analytic fit of the interaction energies is obtained using a many-body expansion method. A coupled-channel quantum reactive scattering approach implemented in hyperspherical coordinates is adopted for the scattering calculations under cold conditions. Results show that the Li + CaF reaction populates several low-lying vibrational levels and many rotational levels of the product LiF molecule and that the reaction is inefficient in the 1-100 mK regime allowing sympathetic cooling of CaF by collisions with cold Li atoms.
A potential energy surface for the lowest quartet electronic state ((4)A(')) of lithium trimer is developed and used to study spin-polarized Li+Li(2) collisions at ultralow kinetic energies. The potential energy surface allows barrierless atom exchange reactions. Elastic and inelastic cross sections are calculated for collisions involving a variety of rovibrational states of Li(2). Inelastic collisions are responsible for trap loss in molecule production experiments. Isotope effects and the sensitivity of the results to details of the potential energy surface are investigated. It is found that for vibrationally excited states, the cross sections are only quite weakly dependent on details of the potential energy surface.