Ultracold<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">L</mml:mi><mml:mi mathvariant="normal">i</mml:mi><mml:mo>+</mml:mo><mml:msub><mml:mrow><mml:mi mathvariant="normal">L</mml:mi><mml:mi mathvariant="normal">i</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:math>Collisions: Bosonic and Fermionic Cases

Cvitaš, Marko T.; Soldán, Pavel; Hutson, Jeremy M.; Honvault, Pascal; Launay, Jean–Michel

doi:10.1103/physrevlett.94.033201

Cited by 113 publications

(129 citation statements)

References 22 publications

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“…Similar conclusions have been found by Lara et al [43,44] for collisions between OH molecules with Rb atoms. The relatively large rate coefficient for the reaction in the zero-temperature limit indicates that barrierless exothermic reactions occur at significant rates at ultracold temperatures, in agreement with similar results for alkali-metal atom -diatom reactions [21,22,23,24,25,26,27,28,29]. Fig.…”

Section: A Cross Sections and Rate Coefficientssupporting

confidence: 73%

“…The typical rate coefficients of these reactions are on the order of 10 −11 − 10 −10 cm 3 molecule −1 s −1 depending on the collisional system, the temperature and the vibrational levels probed. All these experimental studies indicate that inelastic and reactive processes occur at significant rates at ultracold temperatures, in accordance with theoretical predictions on barrier reactions [15,16,17,18,19,20] as well as a number of alkali-metal atom -dimer systems [21,22,23,24,25,26,27,28,29,30] such as Li + Li 2 , Na + Na 2 and K + K 2 which proceeds without an energy barrier in the entrance channel. The alkali-metal systems are characterized by triatomic complexes with deep potential wells which make them challenging systems for accurate quantum calculations.…”

Section: Introductionsupporting

confidence: 58%

“…At E c = 10 −6 K the reactive rate coefficient is two orders of magnitude larger than the elastic one. This is reminiscent of other exothermic barrierless systems such as alkali-metal atom -diatom collisions [21,22,23,24,25,26,27,28,29]. At energies between E c = 0.01 K and 30 K, elastic and reactive rate coefficients are of comparable magnitude.…”

Section: A Cross Sections and Rate Coefficientsmentioning

confidence: 96%

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Formation of molecular oxygen in ultracoldO+OHcollisions

2009

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We discuss the formation of molecular oxygen in ultracold collisions between hydroxyl radicals and atomic oxygen. A time-independent quantum formalism based on hyperspherical coordinates is employed for the calculations. Elastic, inelastic and reactive cross sections as well as the vibrational and rotational populations of the product O2 molecules are reported. A J-shifting approximation is used to compute the rate coefficients. At temperatures T = 10 − 100 mK for which the OH molecules have been cooled and trapped experimentally, the elastic and reactive rate coefficients are of comparable magnitude, while at colder temperatures, T < 1 mK, the formation of molecular oxygen becomes the dominant pathway. The validity of a classical capture model to describe cold collisions of OH and O is also discussed. While very good agreement is found between classical and quantum results at T = 0.3 K, at higher temperatures, the quantum calculations predict a larger rate coefficient than the classical model, in agreement with experimental data for the O + OH reaction. The zero-temperature limiting value of the rate coefficient is predicted to be about 6 × 10 −12 cm 3 molecule −1 s −1 , a value comparable to that of barrierless alkali-metal atom -dimer systems and about a factor of five larger than that of the tunneling dominated F + H2 reaction.

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Section: A Cross Sections and Rate Coefficientssupporting

confidence: 73%

Section: Introductionsupporting

confidence: 58%

Section: A Cross Sections and Rate Coefficientsmentioning

confidence: 96%

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Formation of molecular oxygen in ultracoldO+OHcollisions

2009

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“…Further computational improvements must be implemented before we can extend this approach to the more complicated cases of alkali atoms, where the larger number of sharp nonadiabatic avoided crossings pose difficulties. Further, in alkali systems, we expect that the three-body term will play a much larger role as has been recognized previously [52,53]. This work shows, however, that retardation cannot be neglected in calculations of ultracold scattering properties based on ab initio potential energies, especially for three-body recombination.…”

Section: Discussionmentioning

confidence: 86%

Adiabatic hyperspherical study of triatomic helium systems

2008

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The 4 He 3 system is studied using the adiabatic hyperspherical representation. We adopt the current state-of-the-art helium interaction potential including retardation and the nonadditive three-body term, to calculate all low-energy properties of the triatomic 4 He system. The bound state energies of the 4 He trimer are computed as well as the 4 He+ 4 He 2 elastic scattering cross sections, the three-body recombination and collision induced dissociation rates at finite temperatures. We also treat the system that consists of two 4 He and one 3 He atoms, and compute the spectrum of the isotopic trimer 4 He 2 3 He, the 3 He+ 4 He 2 elastic scattering cross sections, the rates for three-body recombination and the collision induced dissociation rate at finite temperatures.The effects of retardation and the nonadditive three-body term are investigated. Retardation is found to be significant in some cases, while the three-body term plays only a minor role for these systems.

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“…Regarding the former, the Wigner threshold laws provide a behaviour for the l cross-section below the centrifugal barrier given by E l−1/2 . If, after the barrier were overcome, the reaction probability reached quickly the limit value of one, the behaviour should follow a 1/k 2 dependence, that is ∼ E −1 [67][68][69]. This would result as a "bump" in the cross-sections.…”

Section: The Structures In the Cross-sectionsmentioning

confidence: 99%

Reaching the cold regime: S(1D) + H2 and the role of long-range interactions in open shell reactive collisions

Lara

Dayou

Launay

2011

Phys. Chem. Chem. Phys.

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Reactive cross-sections for the collision of open shell S( 1 D) atoms with ortho-and para-hydrogen, in the kinetic energy range 1−120 K, have been calculated using the hyperspherical quantum reactive scattering method developed by Launay et al. [Chem. Phys. Lett. 169, 473 (1990)]. Short-range interactions, described using the ab initio potential energy surface by Ho et al., were complemented with an accurate description of the longrange interactions, where the main electrostatic (∼ R −5 ) and dispersion (∼ R −6 ) contributions were considered. This allows the comparison with recent experimental measurements of rate constants and excitation functions for the title reaction at low temperatures [Berteloite et al., accepted in Phys. Rev. Lett., 2010]. The agreement is fairly good. The behavior in the considered energy range can be understood on the average in terms of a classical Langevin (capture) model, where the centrifugal barriers determine the amount of reactive flux which reaches the barrierless transition state. Additionally, the structure of the van der Waals well provides temporal trapping at short distances thus allowing the system to find its way to the reaction at some classically-forbidden energies. Interestingly, the cross-section for para-hydrogen shows clearly oscillating features associated to the opening of new partial waves and to shape resonances which may be amenable to experimental detection.

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UltracoldLi+Li2Collisions: Bosonic and Fermionic Cases

Cited by 113 publications

References 22 publications

Formation of molecular oxygen in ultracoldO+OHcollisions

Formation of molecular oxygen in ultracoldO+OHcollisions

Adiabatic hyperspherical study of triatomic helium systems

Reaching the cold regime: S(1D) + H2 and the role of long-range interactions in open shell reactive collisions

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