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

Sympathetic cooling of NH(X3Σ−) molecules by Rb and Cs atoms at ultralow energies

M. Tacconi, Enrico Bodo, Franco Antonio Gianturco

Published Jan 10, 2007• 21 citations
Publisher

Abstract

The relative size of the elastic cross sections between $\mathrm{NH}$ molecules colliding with Cs and Rb atoms on the lowest potential energy surfaces of spin-stretched quartet symmetry are computed using the full quantum treatment and taking the target molecule to be in its ground rotational state. Results are compared between the two systems under similar dynamics and the Rb atom is found to yield larger cross sections at ultralow energies. The process is seen to be dominated by dispersion interaction and an analysis of the effects on the cross sections induced by changes on the ${C}_{6}$ coefficients is carried out in detail for both systems.

DOI
10.1103/physreva.75.012708

Related papers

Collisions of NH(Σ3−) with Rb and Cs at ultralow energies: A quantum study of rotational cooling efficiency

M. Tacconi, Lola González‐Sánchez, Enrico Bodo +1 more

Using ab initio calculations for the lowest, spin-stretched, quartet potential energy surfaces for Rb and Cs neutral atoms interacting with the $\text{NH}({^{3}\ensuremath{\Sigma}}^{\ensuremath{-}})$ polar target, the cold collision quantum dynamics is analyzed at ultralow energies to examine possible propensity rules existing for the relaxation of either spin or rotational target states (or both) via sympathetic cooling induced by the partner atoms. The specific coupling of Hund's case (b) is adopted for the dynamical treatment of spin and rotational angular momenta and the coupled channel approach is employed to solve the scattering equations. Both rotational and/or spin relaxation cross sections are obtained down to ${10}^{\ensuremath{-}6}\text{ }{\text{cm}}^{\ensuremath{-}1}$ of energy and corresponding cooling rates are analyzed and compared between the two systems.

Physical Review A•Sep 5, 2007•12 citations

Low-energy collisions of NH3 and ND3 with ultracold Rb atoms

Piotr Szymon Żuchowski, Jeremy M. Hutson

We carry out quantum inelastic scattering calculations of collisions of Rb atoms with inverting ${\text{NH}}_{3}$ and ${\text{ND}}_{3}$ molecules in the energy range between 0 and $100\text{ }{\text{cm}}^{\ensuremath{-}1}$, which are important for experiments using velocity-controlled molecular beams to probe scattering resonances. We focus on molecules initially in the upper level of the ammonia inversion doublet for $j=1$, $k=1$, which is low-field seeking and can be controlled in a Stark decelerator. We calculate the integral elastic and state-to-state inelastic cross sections in the coupled-states approximation. We demonstrate the presence of both shape and Feshbach resonances in the elastic and inelastic cross sections at low collision energies and discuss their origin in terms of the bound states of the Rb-${\text{ND}}_{3}$ complex. We also consider elastic and inelastic cross sections in the ultracold regime, using close-coupling calculations, in order to assess the viability of sympathetic cooling of ${\text{ND}}_{3}$ by Rb. The inelastic cross section for relaxation to the lower level of the inversion doublet is smaller than expected for such a strongly coupled system but is still likely to be too large to allow sympathetic cooling for ${\text{ND}}_{3}$ in low-field-seeking states. However, there is a good prospect that sympathetic cooling will be possible for molecules in high-field-seeking states even when the collision partner is a magnetically trapped atom in a low-field-seeking state.

arXiv:0902.4548•Physical Review A•Jun 11, 2009•57 citations

Quenching of internal rotations versus collisional cooling at ultralow energies for weakly interacting partners: Cs 2 (3Σu+) with He3,4

D. Caruso, M. Tacconi, Ersin Yurtsever +1 more

Quantum-scattering calculations at ultralow (close to ${10}^{\ensuremath{-}6}$ cm${}^{\ensuremath{-}1}$) collision energies are carried out for the Cs dimer in its spin-stretched triplet state, interacting with helium. An ab initio potential energy surface is computed and employed, while the target molecule is kept in its ground vibrational state and several excitated initial rotational states are considered in the quantum dynamics. The highly anisotropic interaction is seen to cause, in spite of its weakness, internal energy quenching rates comparable with the efficiency of the collisional cooling of relative kinetic energies. The rates of spin-flip processes are also analyzed and compared with pure rotational quenching events.

Physical Review A•Apr 26, 2010•5 citations

Cold and ultracold NH–NH collisions: The field-free case

Liesbeth M. C. Janssen, Piotr Szymon Żuchowski, Ad van der Avoird +2 more

We present elastic and inelastic spin-changing cross sections for cold and ultracold NH(X (3)Σ(-)) + NH(X (3)Σ(-)) collisions, obtained from full quantum scattering calculations on an accurate ab initio quintet potential-energy surface. Although we consider only collisions in zero field, we focus on the cross sections relevant for magnetic trapping experiments. It is shown that evaporative cooling of both fermionic (14)NH and bosonic (15)NH is likely to be successful for hyperfine states that allow s-wave collisions. The calculated cross sections are very sensitive to the details of the interaction potential, due to the presence of (quasi)bound state resonances. The remaining inaccuracy of the ab initio potential-energy surface therefore gives rise to an uncertainty in the numerical cross-section values. However, based on a sampling of the uncertainty range of the ab initio calculations, we conclude that the exact potential is likely to be such that the elastic-to-inelastic cross-section ratio is sufficiently large to achieve efficient evaporative cooling. This likelihood is only weakly dependent on the size of the channel basis set used in the scattering calculations.

arXiv:1012.0804•The Journal of Chemical Physics•Mar 28, 2011•25 citations

Potential energy surface and cold collision dynamics of Xe-NH(X3∑-) system

Qiao Zheng sup sup, Wang Ya-li, Wu Ming-Wei +2 more

Sympathetic cooling is one of the most promising techniques for producing ultracold molecules from precooled molecules. Previous researches have shown that it is inadequate to use the ultracold alkali-metal atoms as coolant for sympathetic cooling. To explore the possibility of ultracold alkali-earth-metal atoms as coolant, in this paper a theoretical investigation is performed of the cold collision dynamics for Xe-NH(X3∑-) system in magnetic fields. The interaction potential energies of Xe-NH complex are calculated respectively by using the single and double excitation coupled-cluster theory with the noniterative treatment of triple excitations[CCSD(T)] method and complete basis set limit extrapolated method. An analytic express of potential energy surface (PES) is given for the first time. A single global minimum value occurs at R=7.14a0, θ=102.76° with an energy of-153.54 cm-1, and the PES has a weak anisotropy. Combine the ab initio PES with quantum scattering theory, then the cold collisional dynamics of Xe-NH system in a magnetic field will be studied. The elastic and inelastic transition cross sections and their ratios of NH molecules in the lowest low-field following state (n=0, mj=1) under different magnetic fields and collisional energies are calculated. The results show that the elastic cross section is independent of magnetic field, and the inelastic cross section changes with magnetic field, especially at an ultracold temperature. A common rule of thumb is that to successfully implement cooling, the ratio of elastic cross section to inelastic cross section needs to reach 100 at least. The results suggest that it is likely to be a challenging work to perform sympathetic cooling of NH molecule by ultracold Xe atom.

Acta Physica Sinica•Jan 1, 2018•0 citations

Interaction of NH(X Σ−3) Molecules with Rubidium Atoms: Implications for Sympathetic Cooling and the Formation of Extremely Polar Molecules

Pavel Soldán, Jeremy M. Hutson

The Rb-NH interaction is investigated as a prototype for interactions between alkali-metal atoms and stable molecules. For spin-aligned Rb and NH that interact on a quartet surface (4A"), the interaction is relatively weak, with a well depth of 0.078 eV. However, there are also doublet surfaces of ion-pair character that are very much deeper (well depth 1.372 eV). They may be important for atom-molecule collision rates and offer the possibility of forming strongly dipolar molecules by photoassociation. Similar deeply bound ion-pair states are likely to exist for other alkali atom-molecule pairs.

arXiv:cond-mat/0307466•Physical Review Letters•Apr 23, 2004•61 citations
The relative size of the elastic cross sections between NH\mathrm{NH}NH molecules colliding with Cs and Rb atoms on the lowest potential energy surfaces of spin-stretched quartet symmetry are computed using the full quantum treatment and taking the target molecule to be in its ground rotational state. Results are compared between the two systems under similar dynamics and the Rb atom is found to yield larger cross sections at ultralow energies. The process is seen to be dominated by dispersion interaction and an analysis of the effects on the cross sections induced by changes on the C6{C}_{6}C6​ coefficients is carried out in detail for both systems.
Using ab initio calculations for the lowest, spin-stretched, quartet potential energy surfaces for Rb and Cs neutral atoms interacting with the $\text{NH}({^{3}\ensuremath{\Sigma}}^{\ensuremath{-}})$ polar target, the cold collision quantum dynamics is analyzed at ultralow energies to examine possible propensity rules existing for the relaxation of either spin or rotational target states (or both) via sympathetic cooling induced by the partner atoms. The specific coupling of Hund's case (b) is adopted for the dynamical treatment of spin and rotational angular momenta and the coupled channel approach is employed to solve the scattering equations. Both rotational and/or spin relaxation cross sections are obtained down to ${10}^{\ensuremath{-}6}\text{ }{\text{cm}}^{\ensuremath{-}1}$ of energy and corresponding cooling rates are analyzed and compared between the two systems.
We carry out quantum inelastic scattering calculations of collisions of Rb atoms with inverting NH3{\text{NH}}_{3}NH3​ and ND3{\text{ND}}_{3}ND3​ molecules in the energy range between 0 and $100\text{ }{\text{cm}}^{\ensuremath{-}1}$, which are important for experiments using velocity-controlled molecular beams to probe scattering resonances. We focus on molecules initially in the upper level of the ammonia inversion doublet for j=1j=1j=1, k=1k=1k=1, which is low-field seeking and can be controlled in a Stark decelerator. We calculate the integral elastic and state-to-state inelastic cross sections in the coupled-states approximation. We demonstrate the presence of both shape and Feshbach resonances in the elastic and inelastic cross sections at low collision energies and discuss their origin in terms of the bound states of the Rb-ND3{\text{ND}}_{3}ND3​ complex. We also consider elastic and inelastic cross sections in the ultracold regime, using close-coupling calculations, in order to assess the viability of sympathetic cooling of ND3{\text{ND}}_{3}ND3​ by Rb. The inelastic cross section for relaxation to the lower level of the inversion doublet is smaller than expected for such a strongly coupled system but is still likely to be too large to allow sympathetic cooling for ND3{\text{ND}}_{3}ND3​ in low-field-seeking states. However, there is a good prospect that sympathetic cooling will be possible for molecules in high-field-seeking states even when the collision partner is a magnetically trapped atom in a low-field-seeking state.
Quantum-scattering calculations at ultralow (close to ${10}^{\ensuremath{-}6}$ cm${}^{\ensuremath{-}1}$) collision energies are carried out for the Cs dimer in its spin-stretched triplet state, interacting with helium. An ab initio potential energy surface is computed and employed, while the target molecule is kept in its ground vibrational state and several excitated initial rotational states are considered in the quantum dynamics. The highly anisotropic interaction is seen to cause, in spite of its weakness, internal energy quenching rates comparable with the efficiency of the collisional cooling of relative kinetic energies. The rates of spin-flip processes are also analyzed and compared with pure rotational quenching events.
We present elastic and inelastic spin-changing cross sections for cold and ultracold NH(X (3)Σ(-)) + NH(X (3)Σ(-)) collisions, obtained from full quantum scattering calculations on an accurate ab initio quintet potential-energy surface. Although we consider only collisions in zero field, we focus on the cross sections relevant for magnetic trapping experiments. It is shown that evaporative cooling of both fermionic (14)NH and bosonic (15)NH is likely to be successful for hyperfine states that allow s-wave collisions. The calculated cross sections are very sensitive to the details of the interaction potential, due to the presence of (quasi)bound state resonances. The remaining inaccuracy of the ab initio potential-energy surface therefore gives rise to an uncertainty in the numerical cross-section values. However, based on a sampling of the uncertainty range of the ab initio calculations, we conclude that the exact potential is likely to be such that the elastic-to-inelastic cross-section ratio is sufficiently large to achieve efficient evaporative cooling. This likelihood is only weakly dependent on the size of the channel basis set used in the scattering calculations.
Sympathetic cooling is one of the most promising techniques for producing ultracold molecules from precooled molecules. Previous researches have shown that it is inadequate to use the ultracold alkali-metal atoms as coolant for sympathetic cooling. To explore the possibility of ultracold alkali-earth-metal atoms as coolant, in this paper a theoretical investigation is performed of the cold collision dynamics for Xe-NH(X3∑-) system in magnetic fields. The interaction potential energies of Xe-NH complex are calculated respectively by using the single and double excitation coupled-cluster theory with the noniterative treatment of triple excitations[CCSD(T)] method and complete basis set limit extrapolated method. An analytic express of potential energy surface (PES) is given for the first time. A single global minimum value occurs at R=7.14a0, θ=102.76° with an energy of-153.54 cm-1, and the PES has a weak anisotropy. Combine the ab initio PES with quantum scattering theory, then the cold collisional dynamics of Xe-NH system in a magnetic field will be studied. The elastic and inelastic transition cross sections and their ratios of NH molecules in the lowest low-field following state (n=0, mj=1) under different magnetic fields and collisional energies are calculated. The results show that the elastic cross section is independent of magnetic field, and the inelastic cross section changes with magnetic field, especially at an ultracold temperature. A common rule of thumb is that to successfully implement cooling, the ratio of elastic cross section to inelastic cross section needs to reach 100 at least. The results suggest that it is likely to be a challenging work to perform sympathetic cooling of NH molecule by ultracold Xe atom.
The Rb-NH interaction is investigated as a prototype for interactions between alkali-metal atoms and stable molecules. For spin-aligned Rb and NH that interact on a quartet surface (4A"), the interaction is relatively weak, with a well depth of 0.078 eV. However, there are also doublet surfaces of ion-pair character that are very much deeper (well depth 1.372 eV). They may be important for atom-molecule collision rates and offer the possibility of forming strongly dipolar molecules by photoassociation. Similar deeply bound ion-pair states are likely to exist for other alkali atom-molecule pairs.