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 Letters

Quenching of H2 Vibrations in Ultracold 3He and 4He Collisions

N. Balakrishnan, Robert C. Forrey, A. Dalgarno

Published Apr 13, 1998• 166 citations
Publisher

Abstract

We present results of quantum mechanical scattering calculations including full rovibrational coupling on the relaxation of vibrationally excited ${\mathrm{H}}_{2}$ molecules in collision with ultracold ${}^{3}\mathrm{He}$ and ${}^{4}\mathrm{He}$ atoms. The exothermic vibrational deactivation cross sections exhibit minima at translational temperatures near 10 K and show an inverse velocity dependence in accordance with Wigner's threshold law in the limit of zero kinetic energy. The corresponding rate coefficients exhibit minima before attaining constant values below ${10}^{\ensuremath{-}3}$ K. The rate coefficients increase by 3 orders of magnitude when the initial vibrational level of the molecule is raised from $v\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ to $v\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}10$. The results suggest that quasibound resonance states of ${}^{3}{\mathrm{HeH}}_{2}$ and ${}^{4}{\mathrm{HeH}}_{2}$ exist, associated with each excited vibrational state of ${\mathrm{H}}_{2}$, and that both the triatomic species ${}^{3}{\mathrm{HeH}}_{2}$ and ${}^{4}{\mathrm{HeH}}_{2}$ have one bound vibrational state.

DOI
10.1103/physrevlett.80.3224

Related papers

Vibrational quenching of N2(ν=1,jrot=j) by 3He: Surface and close-coupling calculations at very low energy

Thierry Stoecklin, A. Voronin, Jean Claude Rayez

A quantum-mechanical investigation of the vibrational deactivation of ${}^{14}{\mathrm{N}}_{2}(\ensuremath{\nu}=1,{j}_{\mathrm{rot}}=j)$ in the ultracold collisions with ${}^{3}\mathrm{He}$ atoms is presented. Ab initio potential-energy calculations are carried out at BCCD(T) level and a global three-dimensional potential-energy surface is obtained by fitting ab initio points within the reproducing kernel Hilbert space method. Close coupling scattering calculations are performed at collision energy ranging from ${10}^{\ensuremath{-}6}$ to 2000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. It is shown that the potential-energy surface supports a series of shape and Feshbach resonances. Their influence on the behavior of elastic and inelastic cross sections and quenching rate coefficients is discussed. It is demonstrated that, similar to the ${\mathrm{H}\mathrm{e}\ensuremath{-}\mathrm{O}}_{2}$ system, the rate coefficients exhibit three different regimes: Wigner regime at very low temperatures, van der Waals regime at intermediate temperatures due to series of resonances, and the usual rovibration--translation energy transfer regime at high temperatures.

Physical Review A•Oct 3, 2002•57 citations

Rotational relaxation in ultracold He+BH collisions

Ming-Yan Gong, Xiaotao Xu, Eryin Feng

Collisions of cold and ultracold BH in the ν = 0 level with the He atom are investigated using the quantum mechanical scattering formulation. The elastic and the inelastic cross sections are calculated using the two-dimensional ab initio potential energy surface. It is shown that the elastic cross section is larger than the inelastic one. When the collision energy is very low, the elastic cross section follows the Wigner threshold law and is one order of magnitude larger than that of He-O 2 , while it is much smaller than that of He-H 2 . The efficiency of the rotationally quenching state is given. The Δ j = −1 transition is most efficient. The resonances are also found to occur at about the same translational energy (0.1–1 cm −1 ), which gives rise to steps in the rate coefficient at temperatures around 0.1–1 K.

Chinese Physics B•Nov 1, 2011•1 citation

Cold He+H2 collisions near dissociation

Akiko Mack, Tricia K. Clark, Robert C. Forrey +3 more

Cross sections for $\mathrm{He}+{\mathrm{H}}_{2}$ collisions are reported for rovibrational states near dissociation at translational energies less than $1000\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. In contrast to our previously reported cross sections for lower-lying initial rotational states, the excited rotational states near dissociation give rise to shape resonances for energies between 0.001 and $1\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. The emergence of these resonances with increasing rotational level is opposite to the trend found for $\mathrm{He}+\mathrm{C}\mathrm{O}$ where the shape resonance strength decreases with rotational level for low-lying states. Quasiresonant energy transfer and low energy excitation thresholds are also discussed and it is found that there are 11 rovibrationally excited states that are stable against collision at ultracold temperatures.

Physical Review A•Nov 30, 2006•23 citations

Strong isotope effect in ultracold collision of N2+ ( ν=1 , j=0 ) with He: A case study of virtual-state scattering

Thierry Stoecklin, A. Voronin

A comparative study of the vibrational deactivation of $^{14}\mathrm{N}_{2}^{+}$ ($\ensuremath{\nu}=1$, $j=0$) in collision with $^{3}\mathrm{He}$ and $^{4}\mathrm{He}$ atoms is investigated. Close-coupling calculations are carried out in the ${10}^{\ensuremath{-}6}--2000\text{\ensuremath{-}}{\mathrm{cm}}^{\ensuremath{-}1}$ kinetic energy range. At very low kinetic energy, it is found that the cross sections for the collision involving $^{3}\mathrm{He}$ is strongly enhanced by the presence of a virtual state associated with the van der Waals well. The change of mass from $^{3}\mathrm{He}$ to $^{4}\mathrm{He}$ also erases a strong shape resonance at $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ supported by the van der Waals well. As a result, the law of variation of the associated vibrational quenching rate coefficient is found to be very different for these two systems. This behavior is further analyzed by drawing the real part of the scattering length as a function of the variable mass of a fictitious He atom. Two zero energy resonances are identified for a mass of, respectively, about 3.18 and 3.85 atomic mass units.

Physical Review A•Oct 26, 2005•34 citations

Quantum Dynamics of Ultracold Na+ Na2 Collisions

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

Ultracold collisions between spin-polarized Na atoms and vibrationally excited ${\mathrm{N}\mathrm{a}}_{2}$ molecules are investigated theoretically, using a reactive scattering formalism (including atom exchange). Calculations are carried out on both pairwise additive and nonadditive potential energy surfaces for the quartet electronic state. The Wigner threshold laws are followed for energies below ${10}^{\ensuremath{-}5}\text{ }\mathrm{K}$. Vibrational relaxation processes dominate elastic processes for temperatures below ${10}^{\ensuremath{-}3}--{10}^{\ensuremath{-}4}\text{ }\mathrm{K}$. For temperatures below ${10}^{\ensuremath{-}5}\text{ }\mathrm{K}$, the rate coefficients for vibrational relaxation ($v=1\ensuremath{\rightarrow}0$) are $4.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ and $5.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }{\mathrm{c}\mathrm{m}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ for the additive and nonadditive potentials, respectively. The large difference emphasizes the importance of using accurate potential energy surfaces for such calculations.

arXiv:cond-mat/0205077•Physical Review Letters•Sep 18, 2002•145 citations

Ultracold collisions for atom--diatom systems with a reaction barrier

I. Simbotin

Theoretical results for ultracold atom-molecule collisions involving exoergic reactions are presented. Systems with a reaction barrier are considered; specifically, we report the results of extensive computations for D + H 2 and Cl + H2. We analyzed the extreme situation of translationally cold collisions between an atom and an internally hot molecule; namely, for D + H2 we explored the role played by the internal vibrational excitation of the diatomic target for initial states H2(υ) with υ = 0,1,2,…, 8. The υ-dependence of the zero-temperature limit of the reaction rate coefficient shows two distinct regimes: a barrier dominated regime for υ < 4, and a barrierless regime for υ > 4. Also, for highly excited initial states, the distribution over the final states of the products shows an approximate conservation of the internal vibrational energy. For Cl + H2 we studied in detail the isotopic effect by varying continuously the mass of H, which allowed us to find resonance effects in the threshold behavior of cross sections. These resonances are caused by long-lived van der Waals complexes (Cl···H2) which have vanishingly small binding energy, or by virtual states of the Cl···H 2 complex. ^

•Jan 1, 2012•0 citations
We present results of quantum mechanical scattering calculations including full rovibrational coupling on the relaxation of vibrationally excited H2{\mathrm{H}}_{2}H2​ molecules in collision with ultracold 3He{}^{3}\mathrm{He}3He and 4He{}^{4}\mathrm{He}4He atoms. The exothermic vibrational deactivation cross sections exhibit minima at translational temperatures near 10 K and show an inverse velocity dependence in accordance with Wigner's threshold law in the limit of zero kinetic energy. The corresponding rate coefficients exhibit minima before attaining constant values below 10\ensuremath−3{10}^{\ensuremath{-}3}10\ensuremath−3 K. The rate coefficients increase by 3 orders of magnitude when the initial vibrational level of the molecule is raised from v=1v\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1v=1 to v=10v\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}10v=10. The results suggest that quasibound resonance states of 3HeH2{}^{3}{\mathrm{HeH}}_{2}3HeH2​ and 4HeH2{}^{4}{\mathrm{HeH}}_{2}4HeH2​ exist, associated with each excited vibrational state of H2{\mathrm{H}}_{2}H2​, and that both the triatomic species 3HeH2{}^{3}{\mathrm{HeH}}_{2}3HeH2​ and 4HeH2{}^{4}{\mathrm{HeH}}_{2}4HeH2​ have one bound vibrational state.
A quantum-mechanical investigation of the vibrational deactivation of ${}^{14}{\mathrm{N}}_{2}(\ensuremath{\nu}=1,{j}_{\mathrm{rot}}=j)$ in the ultracold collisions with 3He{}^{3}\mathrm{He}3He atoms is presented. Ab initio potential-energy calculations are carried out at BCCD(T) level and a global three-dimensional potential-energy surface is obtained by fitting ab initio points within the reproducing kernel Hilbert space method. Close coupling scattering calculations are performed at collision energy ranging from ${10}^{\ensuremath{-}6}$ to 2000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. It is shown that the potential-energy surface supports a series of shape and Feshbach resonances. Their influence on the behavior of elastic and inelastic cross sections and quenching rate coefficients is discussed. It is demonstrated that, similar to the ${\mathrm{H}\mathrm{e}\ensuremath{-}\mathrm{O}}_{2}$ system, the rate coefficients exhibit three different regimes: Wigner regime at very low temperatures, van der Waals regime at intermediate temperatures due to series of resonances, and the usual rovibration--translation energy transfer regime at high temperatures.
Collisions of cold and ultracold BH in the ν = 0 level with the He atom are investigated using the quantum mechanical scattering formulation. The elastic and the inelastic cross sections are calculated using the two-dimensional ab initio potential energy surface. It is shown that the elastic cross section is larger than the inelastic one. When the collision energy is very low, the elastic cross section follows the Wigner threshold law and is one order of magnitude larger than that of He-O 2 , while it is much smaller than that of He-H 2 . The efficiency of the rotationally quenching state is given. The Δ j = −1 transition is most efficient. The resonances are also found to occur at about the same translational energy (0.1–1 cm −1 ), which gives rise to steps in the rate coefficient at temperatures around 0.1–1 K.
Cross sections for He+H2\mathrm{He}+{\mathrm{H}}_{2}He+H2​ collisions are reported for rovibrational states near dissociation at translational energies less than $1000\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. In contrast to our previously reported cross sections for lower-lying initial rotational states, the excited rotational states near dissociation give rise to shape resonances for energies between 0.001 and $1\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. The emergence of these resonances with increasing rotational level is opposite to the trend found for He+CO\mathrm{He}+\mathrm{C}\mathrm{O}He+CO where the shape resonance strength decreases with rotational level for low-lying states. Quasiresonant energy transfer and low energy excitation thresholds are also discussed and it is found that there are 11 rovibrationally excited states that are stable against collision at ultracold temperatures.
A comparative study of the vibrational deactivation of 14N2+^{14}\mathrm{N}_{2}^{+}14N2+​ ($\ensuremath{\nu}=1$, j=0j=0j=0) in collision with 3He^{3}\mathrm{He}3He and 4He^{4}\mathrm{He}4He atoms is investigated. Close-coupling calculations are carried out in the ${10}^{\ensuremath{-}6}--2000\text{\ensuremath{-}}{\mathrm{cm}}^{\ensuremath{-}1}$ kinetic energy range. At very low kinetic energy, it is found that the cross sections for the collision involving 3He^{3}\mathrm{He}3He is strongly enhanced by the presence of a virtual state associated with the van der Waals well. The change of mass from 3He^{3}\mathrm{He}3He to 4He^{4}\mathrm{He}4He also erases a strong shape resonance at $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ supported by the van der Waals well. As a result, the law of variation of the associated vibrational quenching rate coefficient is found to be very different for these two systems. This behavior is further analyzed by drawing the real part of the scattering length as a function of the variable mass of a fictitious He atom. Two zero energy resonances are identified for a mass of, respectively, about 3.18 and 3.85 atomic mass units.
Ultracold collisions between spin-polarized Na atoms and vibrationally excited Na2{\mathrm{N}\mathrm{a}}_{2}Na2​ molecules are investigated theoretically, using a reactive scattering formalism (including atom exchange). Calculations are carried out on both pairwise additive and nonadditive potential energy surfaces for the quartet electronic state. The Wigner threshold laws are followed for energies below ${10}^{\ensuremath{-}5}\text{ }\mathrm{K}$. Vibrational relaxation processes dominate elastic processes for temperatures below ${10}^{\ensuremath{-}3}--{10}^{\ensuremath{-}4}\text{ }\mathrm{K}$. For temperatures below ${10}^{\ensuremath{-}5}\text{ }\mathrm{K}$, the rate coefficients for vibrational relaxation ($v=1\ensuremath{\rightarrow}0$) are $4.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ and $5.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }{\mathrm{c}\mathrm{m}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ for the additive and nonadditive potentials, respectively. The large difference emphasizes the importance of using accurate potential energy surfaces for such calculations.
Theoretical results for ultracold atom-molecule collisions involving exoergic reactions are presented. Systems with a reaction barrier are considered; specifically, we report the results of extensive computations for D + H 2 and Cl + H2. We analyzed the extreme situation of translationally cold collisions between an atom and an internally hot molecule; namely, for D + H2 we explored the role played by the internal vibrational excitation of the diatomic target for initial states H2(υ) with υ = 0,1,2,…, 8. The υ-dependence of the zero-temperature limit of the reaction rate coefficient shows two distinct regimes: a barrier dominated regime for υ < 4, and a barrierless regime for υ > 4. Also, for highly excited initial states, the distribution over the final states of the products shows an approximate conservation of the internal vibrational energy. For Cl + H2 we studied in detail the isotopic effect by varying continuously the mass of H, which allowed us to find resonance effects in the threshold behavior of cross sections. These resonances are caused by long-lived van der Waals complexes (Cl···H2) which have vanishingly small binding energy, or by virtual states of the Cl···H 2 complex. ^