<i>Ab initio</i>interaction potentials and scattering lengths for ultracold mixtures of metastable helium and alkali-metal atoms

Kędziera, Dariusz; Mentel, Ł. M.; Żuchowski, Piotr S.; Knoop, Steven

doi:10.1103/physreva.91.062711

Cited by 9 publications

(17 citation statements)

References 47 publications

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“…More accurate experimental data for this reaction system will thus aid the theoretical description of potential energy surfaces and the associated quantum dynamics calculations. With a total of only five electrons involved, He*-Li represents a collision system especially suitable for accurate quantum-chemical calculations 6,7 .…”

Section: Introductionmentioning

confidence: 99%

Penning collisions between supersonically expanded metastable He atoms and laser-cooled Li atoms

Grzesiak

Momose

Stienkemeier

et al. 2019

The Journal of Chemical Physics

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We describe an experimental setup comprised of a discharge source for supersonic beams of metastable helium atoms and a magneto-optical trap (MOT) for ultracold lithium atoms that makes it possible to study Penning ionization and associative ionization processes at high ion count rates. The cationic reaction products are analyzed using a novel ion detection scheme which allows for mass selection, a high ion extraction efficiency and a good collision-energy resolution. The influence of elastic He-Li collisions on the steady-state Li atom number in the MOT is described, and the collision data are used to estimate the excitation efficiency of the discharge source. We also show that Penning collisions can be directly used to probe the temperature of the Li cloud without the need for an additional time-resolved absorption or fluorescence detection system.

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Section: Introductionmentioning

confidence: 99%

Penning collisions between supersonically expanded metastable He atoms and laser-cooled Li atoms

Grzesiak

Momose

Stienkemeier

et al. 2019

The Journal of Chemical Physics

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“…Finite temperature corrections to the zero-temperature limit are expected to be small in our case, as our temperature of 22 µK is well below the van der Waals energy and p-wave centrifugal barrier. The only exceptions would be in case of a potential resonance (|a| >>ā) or a p-wave shape resonance (a ≈ 2ā) in one of the two potentials, which is not the case for the quartet potential [13,18]. The knowledge of the doublet potential is very limited, and the doublet scattering length is unknown.…”

Section: Spin-exchange Collisionsmentioning

confidence: 99%

Quantum-state-controlled Penning-ionization reactions between ultracold alkali-metal and metastable helium atoms

2016

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In an ultracold, optically trapped mixture of 87 Rb and metastable triplet 4 He atoms we have studied trap loss for different spin-state combinations, for which interspecies Penning ionization is the main two-body loss process. We observe long trapping lifetimes for the purely quartet spinstate combination, indicating strong suppression of Penning ionization loss by at least two orders of magnitude. For the other spin-mixtures we observe short lifetimes that depend linearly on the doublet character of the entrance channel. We compare the extracted loss rate coefficient with recent predictions of multichannel quantum-defect theory for reactive collisions involving a strong exothermic loss channel and find near-universal loss for doublet scattering. Our work demonstrates control of Penning ionization reactive collisions by internal atomic state preparation.Ultracold inelastic and reactive collisions are important processes in atomic and molecular samples [1,2], determining their trapping lifetimes and the success of evaporative and sympathetic cooling. Conversely, measurements of these lifetimes reveal the rate coefficients of the dominant inelastic or reactive collision processes, opening the fields of ultracold few-body physics [3,4] and ultracold chemistry [5,6]. The ultracold regime offers exquisite control over the initial internal and external quantum states, and the possibility to experimentally control collision properties or even steer chemical reactions with external fields [7].Understanding of inelastic and reactive collisions is in general very difficult due to the many degrees of freedom involved. This has motivated recent work based on multichannel quantum-defect theory (MQDT) [8][9][10], in which analytic expressions of collision rates were derived in the case of a strong exothermic reactive channel. In particular, if the probability of an inelastic or reactive process in the short-range part of the collision is 100%, i. e. if P re = 1, theory predicts universal rate constants that only depend on the reduced mass of the collision partners and the leading long-range coefficient [8,9], independent of the complicated short-range dynamics. If the reaction probability is less than 100% (P re < 1), still only two parameters are required to include the (nonuniversal) short-range physics, i. e. the scattering length a and P re [10]. These analytical models have been applied to atom-exchange reactions between ground state KRb molecules below 1 µK [5,8], and Penning ionization reactions between argon and helium atoms in the metastable triplet 2 3 S 1 state (He * ) in merged-beam experiments from 10 mK up to 30 K [10,11].In this Rapid Communication we study ultracold Penning ionizing collisions between He * atoms (internal energy 19.8 eV) and alkali atoms A in their electronic ground state:

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“…simultaneous MW (alkali-metal) and RF (He*) evaporative cooling), ultracold bosonic 4 He * and bosonic alkali-metal mixtures all seem possible. For the fermionic alkali-metal atoms, the cooling strategy will rely on sympathetic cooling with 4 He * and thus depend on a favorable interspecies quartet scattering length [49]. Similarly, for fermionic 3 He * and bosonic alkali-metal mixtures, realizing two-species quantum degeneracy also depends on the quartet scattering length.…”

Section: Realizing a Bec Ofmentioning

confidence: 99%

“…The gradient is then ramped up to 120 G/cm in 1 s. We typically transfer about 30 to 40% of the atoms of both species from the 3D-MOT into the magnetic trap. Since sympathetic cooling is not efficient due to the small interspecies scattering length and large mass ratio [49,57], we perform simultaneous MW-induced (Rb) and RF-induced (He * ) forced evaporative cooling in the QMT. To generate the MW frequencies, we use a 6.8 GHz phase-locked oscillator (Amplus PLO) mixed with the frequency doubled output of a tunable 80 MHz signal generator.…”

Section: Simultaneous Evaporative Cooling In the Qmtmentioning

confidence: 99%

“…The scattering properties of He * +alkali-metal collisions are described by a shallow quartet 4 Σ + potential and a deeper doublet 2 Σ + potential. Accurate ab initio calculations of the quartet 4 Σ + potentials and the corresponding quartet scattering lengths have recently become available for Li, K, Na and Rb [49], and while most of the doublet 2 Σ + potentials have been studied experimentally and theoretically in the past (see e.g. [50][51][52][53][54]), the doublet scattering lengths are unknown.…”

Section: Introductionmentioning

confidence: 99%

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An ultracold, optically trapped mixture of 87Rb and metastable 4He atoms

et al. 2017

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Abstract. We report on the realization of an ultracold (<25 μK) mixture of rubidium ( 87 Rb) and metastable triplet helium ( 4 He) in an optical dipole trap. Our scheme involves laser cooling in a dual-species magneto-optical trap, simultaneous MW-and RF-induced forced evaporative cooling in a quadrupole magnetic trap, and transfer to a single-beam optical dipole trap. We observe long trapping lifetimes for the doubly spin-stretched spin-state mixture and measure much shorter lifetimes for other spin-state combinations. We discuss prospects for realizing quantum degenerate mixtures of alkali-metal and metastable helium atoms.

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Ab initiointeraction potentials and scattering lengths for ultracold mixtures of metastable helium and alkali-metal atoms

Cited by 9 publications

References 47 publications

Penning collisions between supersonically expanded metastable He atoms and laser-cooled Li atoms

Penning collisions between supersonically expanded metastable He atoms and laser-cooled Li atoms

Quantum-state-controlled Penning-ionization reactions between ultracold alkali-metal and metastable helium atoms

An ultracold, optically trapped mixture of 87Rb and metastable 4He atoms

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