Universal Rate Constants for Reactive Collisions of Ultracold Molecules

Idziaszek, Zbigniew; Julienne, Paul S.

doi:10.1103/physrevlett.104.113202

Cited by 223 publications

(413 citation statements)

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“…In this regard, recently proposed LR parametrization procedures [9,[11][12][13] Fitting experimental data, these models are able to predict nonmeasured values providing some insight into the underlying interactions. In particular, the approach by Jachymski et al, based on multichannel quantum-defect theory (MQDT), provides analytical expressions which can be easily compared with experimental data [9,14,15]. The model has been recently applied to a variety of systems [9,16,17].…”

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confidence: 99%

“…We consider collision energies that range from the ultracold regime, where only one partial wave is open, to the Langevin regime where many of them contribute. These calculations allow us to test the model by Jachymsky et al [9,14] by comparison with accurate theoretical results in a realistic atom + diatom system, providing a way to estimate one of the parameters using simple statistical model assumptions, which do not require performing any quantum reactive scattering calculation.The H + + H 2 system is the prototype of ion-molecule reactions, which are usually nearly barrierless and exhibit large cross sections due to their LR, ∝ − C n /R n , n = 4, potentials. At energies below ≈1.7 eV, the proton exchange is the only reactive channel, and the process can be described on the ground adiabatic PES [19][20][21][22].…”

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confidence: 99%

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confidence: 99%

“…Besides, assuming that the interaction of the system is reasonably described by the current PES, we can use our results to test recent methodologies, like the approach in Refs. [9,14].…”

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confidence: 99%

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Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

et al. 2015

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We have calculated accurate quantum reactive and elastic cross sections for the prototypical barrierless reaction D + + H 2 (v = 0, j = 0) using a modified hyperspherical scattering method. The considered kinetic energy ranges from the ultracold to the Langevin regimes. A reaction rate coefficient practically constant in no less than eight orders of magnitude is obtained. The availability of accurate results for this system allows one to test the quantum theory by Jachymski et al. [K. Jachymski, M. Krych, P. S. Julienne, and Z. Idziaszek, Phys. Rev. Lett. 110, 213202 (2013)] in a nonuniversal case. The short-range reaction probability is rationalized using statistical model assumptions and related to a statistical factor. This provides a means to estimate one of the parameters that characterizes ultracold processes from first principles. The increasing availability of cold and ultracold samples of atoms and molecules has sprung great interest in chemical reactions at very low temperatures [1][2][3][4][5]. Although new experimental approaches [5] appear highly promising, advances in the field are hampered by technical problems in producing most molecules at low temperatures and high enough densities. In contrast to neutral species, ions can be easily trapped and cooled. The technology of Coulomb crystals in radiofrequency ion traps [6] and the possibility of combining them with traps for neutrals or with slow molecular beams [7,8] promise great progress in the analysis of ion-neutral reactions in the near future.Theoretical simulations employing standard ab initio approaches are not feasible for most of the systems thus far considered. For heavy systems (more convenient experimentally) there are no potential energy surfaces (PESs) accurate enough to describe processes near thresholds. Additionally, most of exact dynamical treatments face insurmountable problems in such regimes. However, in contrast to short-range (SR) chemical interactions, those occurring at long range (LR) can be more easily calculated. Moreover, theoretical approaches based only on the knowledge of the LR part of the PES have been able to describe recent experimental findings nearly quantitatively [1,9]. Indeed, processes at very low collision energies favor LR interactions, leading to the idea of universality in extreme cases [10]: the result of the collision depends exclusively on the LR behavior and not on the details of the PES. In this regard, recently proposed LR parametrization procedures [9,[11][12][13] Fitting experimental data, these models are able to predict nonmeasured values providing some insight into the underlying interactions. In particular, the approach by Jachymski et al., based on multichannel quantum-defect theory (MQDT), provides analytical expressions which can be easily compared with experimental data [9,14,15]. The model has been recently applied to a variety of systems [9,16,17]. In particular, for the Penning ionization of Ar by He( 3 S) [5], the rate coefficients have been fitted in a wide range of collision ener...

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confidence: 99%

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confidence: 99%

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confidence: 99%

“…Besides, assuming that the interaction of the system is reasonably described by the current PES, we can use our results to test recent methodologies, like the approach in Refs. [9,14].…”

mentioning

confidence: 99%

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Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

et al. 2015

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“…With polar molecules, two-body chemical reactions can lead to loss; for example, the reaction 2AB → A 2 +B 2 can be exothermic. A simple model that describes these chemical reactions is based on multichannel quantum-defect theory (MQDT) [63], and assumes that once two molecules get to sufficiently short range, they react with high probability. In the limit that this probability is unity, the chemical reactions are universal and can be described with knowledge of only the long-range part of the potential.…”

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New frontiers for quantum gases of polar molecules

et al. 2016

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The field of ultracold quantum matter has burgeoned over the last few decades, thanks to the growing capabilities for atomic systems to be probed and manipulated with exquisite control. Researchers can now precisely create and study quantum manybody states that are effectively isolated from the external environment. Much of the work in ultracold matter has focused on systems of alkali or alkaline-earth atoms, mainly due to their ease of cooling. Extending this precise control to molecules has seen rapidly increasing interest and activity, as molecules possess additional degrees of freedom that make them useful for tests of fundamental physics, studying ultracold chemistry and collisions, and engineering qualitatively new types of quantum phases and quantum many-body systems. Here, we review one particularly fruitful research direction: the creation and manipulation of ultracold bialkali molecules. The recent success in creating a quantum gas of polar molecules opens many exciting research opportunities. Atomic, Molecular, and Optical (AMO) systems offer experimentalists the ability to precisely control interactions in a quantum many-body system [1,2], and a rich set of experiments has already been performed. Some prominent examples include studies of the BEC-BCS crossover in two-component Fermi gases [3,4,5] and the superfluid-Mott insulator transition in ultracold bosons loaded into a 3D optical lattice [6]. Neutral atomic systems normally have point-like contact interactions that can be parametrized with a single quantity, the scattering length a, which can be tuned via a Feshbach resonance [2]. In recent years, systems with long-range and anisotropic interactions have garnered much attention. One natural example is the dipolar interaction between polar molecules, which is the focus of this Review. Of course, many other experimental platforms are also being pursued that feature long-range interactions, including highly magnetic atoms [7,8], trapped ions The dipolar interaction exhibits several important attributes. First, the energy scales in dipolar systems are usually much larger than those in typical atomic alkali systems, making it easier to study interaction-driven structural properties and non-equilibrium dynamics. Second, and perhaps more importantly, the anisotropic and long-range nature of the interaction allows for the realization of novel quantum phases, especially when the spatial dimensions of the system can be varied with optical lattices. Some of these engineered systems may find relevance to outstanding problems in condensed-matter physics [13,14]; moreover, qualitatively new types of physics can emerge in the presence of long-range interactions [15,16,17,18,19,20,21]. As a specific example of a unique feature of long-range interactions, a spin-1/2 Hamiltonian can be encoded based on a pair of oppositeparity rotational states where dipolar interactions give rise to a direct spin exchange coupling between molecules [22,23]. With this scheme implemented in an optical lattice, many-body spin dynam...

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Effects of Electromagnetic Fields on Molecular Scattering

Krems¹

2016

Advances in Chemical Physics Volume 159

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Universal Rate Constants for Reactive Collisions of Ultracold Molecules

Cited by 223 publications

References 22 publications

Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

Beyond universality: Parametrizing ultracold complex-mediated reactions using statistical assumptions

New frontiers for quantum gases of polar molecules

Effects of Electromagnetic Fields on Molecular Scattering

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