Limit on suppression of ionization in metastable neon traps due to long-range anisotropy

Doery, M. R.; Vredenbregt, E.J.D.; Beek, S. S. Op de; Beijerinck, H.C.W.; Verhaar, B.J.

doi:10.1103/physreva.58.3673

Cited by 24 publications

(30 citation statements)

References 30 publications

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“…[11].) The most important new interaction is the electric quadrupole-quadrupole interaction, as discussed by Doery et al [12]. Under normal conditions, anisotropic interactions between the constituents of a gas tend to be smeared out due to thermal averaging.…”

Section: Introductionmentioning

confidence: 97%

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Tensorial analysis of the long-range interaction between metastable alkaline-earth-metal atoms

Santra

Greene

2003

Phys. Rev. A

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Alkaline-earth atoms in their lowest (nsnp) 3 P 2 state are exceptionally long-lived and can be trapped magnetically. The nonspherical atomic structure leads to anisotropic long-range interactions between two metastable alkaline-earth atoms. The anisotropy affects the rotational motion of the diatomic system and couples states of different rotational quantum numbers. This paper develops a tensorial decomposition of the most important long-range interaction operators, and a systematic inclusion of molecular rotations, in the presence of an external magnetic field. This analysis illuminates the nature of the coupling between the various degrees-of-freedom. The consequences are illustrated by application to a system of practical interest: metastable 88 Sr. Using atomic parameters determined in a nearly-ab initio calculation, we compute adiabatic potential energy curves. The anisotropic interatomic interaction, in combination with the applied magnetic field, is demonstrated to induce the formation of a long-range molecular potential well. This curve correlates to two fully polarized, low-field seeking atoms in a rotational s-wave state. The coupling among molecular rotational states controls the existence of the potential well, and its properties vary as a function of magnetic-field strength, thus allowing the scattering length in this state to be tuned. The scattering length of metastable 88 Sr displays a resonance at a field of 339 Gauss.

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Section: Introductionmentioning

confidence: 97%

“…(1), (11), (12), and (15), corrections to E 0 (Ξ) due to interatomic coupling can be found by diagonalizing…”

Section: A Leading Expansion Terms and Feshbach Formalismmentioning

confidence: 99%

Tensorial analysis of the long-range interaction between metastable alkaline-earth-metal atoms

Santra

Greene

2003

Phys. Rev. A

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“…For the heavier rare gases, however, the metastable state 3 P 2 is formed by an exited s electron and a p 5 core with orbital momentum l = 1. This leads to an anisotropic quadrupole-quadrupole interaction between the colliding atoms that limits the amount of suppression [14]. In the case of neon, suppression rates of 77 for 20 Ne and 83 for 22 Ne, respectively, have been determined [1,12], but no suppression has been found for Kr* [15] and Xe* [16].…”

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confidence: 99%

Heteronuclear collisions between laser-cooled metastable neon atoms

et al. 2012

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We investigate heteronuclear collisions in isotope mixtures of laser-cooled metastable ( 3 P2) neon. Experiments are performed with spin-polarized atoms in a magnetic trap for all two-isotope combinations of the stable neon isotopes 20 Ne, 21 Ne, and 22 Ne. We determine the rate coefficients for heteronuclear ionizing collisions to β21,20 = (3.9 ± 2.7) × 10 −11 cm 3 /s, β22,20 = (2.6 ± 0.7) × 10 −11 cm 3 /s, and β21,22 = (3.9 ± 1.9) × 10 −11 cm 3 /s. We also study heteronuclear elastic collision processes and give upper bounds for heteronuclear thermal relaxation cross sections. This work significantly extends the limited available experimental data on heteronuclear ionizing collisions for laser-cooled atoms involving one or more rare gas atoms in a metastable state. I. INTRODUCTIONDue to their high internal energy which surpasses the ionization energy of almost all neutral atomic and molecular collision partners, metastable rare-gas atoms (Rg*) prepared by laser cooling techniques [1] present a unique class of atoms for the investigation of cold and ultracold collisions [2]. With lifetimes ranging from 14.73 s (neon)[3] to 7870 s (helium) [4], the first excited metastable states present effective ground states for applying standard laser cooling techniques. The resulting extremely low kinetic energy of the laser-cooled atoms (≈ 10 −10 eV) stands in strong contrast to the high internal energy between 8 eV (xenon) and 20 eV (helium). This offers unique conditions not accessible with samples of lasercooled alkali-metal atoms. In particular, the high internal energy of the metastable state allows for Penning (PI) and associative (AI) ionizing collisions,to dominate losses in trapped Rg* samples at high densities. Since direct detection of the collision products (using electron multipliers) as well as of the remaining Rg* atoms is possible with high efficiency, detailed studies of homonuclear ionizing collisions have been carried out for all rare gas elements (see [1] for an overview). Additional motivation for these investigations arises from the fact, that favorable rate coefficients for inelastic but also for elastic collisions are essential for the achievement of quantum degeneracy which for Rg* atoms so far has only been demonstrated for 4 He [5-8] and 3 He [9]. For unpolarized Rg* samples, two-body loss rate coefficients for PI [10] between β = 6 × 10 −11 cm 3 /s for 132 Xe [11] and β = 1 × 10 −9 cm 3 /s for 22 Ne [12] have been measured. Spin polarizing the atoms to a spin-stretched * gerhard.birkl@physik.tu-darmstadt.de state may suppress PI: In a collision of atoms in spinstretched states the total spin of the reactants is larger than the total spin of the products. Thus, if spin is conserved, PI collisions should be significantly reduced. In the case of He* in the 3 S 1 state, a suppression of four orders of magnitude has been observed [7,13]. For the heavier rare gases, however, the metastable state 3 P 2 is formed by an exited s electron and a p 5 core with orbital momentum l = 1. This leads to an anisot...

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“…The effect of the quadrupole-quadrupole interaction on the term energy can be disregarded at values of R ≪ C 6 /C 5 ∼ 10 3 a.u.. The quadrupole-quadrupole correction is discussed by Doery et al [3].…”

Section: (L)mentioning

confidence: 99%

“…Motivated by cold-collision studies of metastable rare-gas atoms [1][2][3][4] and prospects of achieving Bose-Einstein Condensation in these systems [5], we present calculations of long-range dispersion (van der Waals) coefficients for two atoms interacting in the ns(3/2) 2 atomic states (n = 3 for Ne, n = 4 for Ar, n = 5 for Kr, and n = 6 for Xe). The metastable states have long lifetimes, 43 sec for Xe [6], decaying to the ground 1 S 0 state by a weak magnetic-quadrupole transition.…”

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confidence: 99%

Long-range interaction of two metastable rare-gas atoms

Derevianko

Dalgarno

2000

Phys. Rev. A

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We present semiempirical calculations of long-range van der Waals interactions for two interacting metastable rare-gas atoms Ne through Xe. Dispersion coefficients C6 are obtained for homonuclear molecular potentials asymptotically connecting to the ns(3/2)2 + ns(3/2)2 atomic states. The estimated uncertainty of the calculated C6 dispersion coefficients is 4%.Motivated by cold-collision studies of metastable rare-gas atoms [1][2][3][4] and prospects of achieving Bose-Einstein Condensation in these systems [5], we present calculations of long-range dispersion (van der Waals) coefficients for two atoms interacting in the ns(3/2) 2 atomic states (n = 3 for Ne, n = 4 for Ar, n = 5 for Kr, and n = 6 for Xe). The metastable states have long lifetimes, 43 sec for Xe [6], decaying to the ground 1 S 0 state by a weak magnetic-quadrupole transition. With such a long lifetime the metastable atom behaves as an effective ground state in experiments. Compared to alkali-metal systems, an attractive feature of the noble gas atoms is the availability of isotopes with zero nuclear spin. The lack of hyperfine structure leads to a substantial simplification of molecular potentials, though some complexity arises due to the nonvanishing total electron angular momentum (J=2) of the metastable state. The anisotropy leads to fifteen distinct long-range molecular states connecting to the ns(3/2) 2 + ns(3/2) 2 asymptotic configuration.Our theoretical treatment of long-range interactions is similar to recent high-precision calculations of van der Waals coefficients for alkali-metal atoms [7]. By using many-body methods and accurate experimental matrix elements for the principal transitions, leading dispersion coefficients C 6 were determined to an accuracy better than 1% for Na, K, and Rb, and of 1% for Cs and 1.5% for Fr. The semiempirical values of C 6 coefficients for metastable noble-gas atoms obtained here have an estimated uncertainty of 4%. The approach relies on the determination of dynamic polarizability functions. To construct the polarizabilities we combine experimental lifetime [8][9][10][11][12][13][14][15] and energy data of the excited states with accurate semiempirical dynamic polarizabilities of the ground states of noble-gas atoms [16]. The theoretical lifetimes and branching ratios [17] are adjusted to reproduce the measured static polarizabilities [18], which are known with a 2% uncertainty. We estimated the additional small contributions within the Dirac-HartreeFock framework. The resulting polarizabilities satisfy the Thomas-Reiche-Kuhn oscillator strength sum rule.The Racah notation for atomic levels is used. The particle-hole states are labeled as nℓ(K) J or nℓ ′ (K) J , where n and ℓ are the principal and the orbital angular momentum quantum numbers of the valence electron and K = J c + ℓ, where J c is the angular momentum of the core. The primed configurations converge to a Rydberg series limit with a hole in the (n − 1)p 1/2 state, and the unprimed to a hole in the (n − 1)p 3/2 state. The manifold of the lowest n...

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Limit on suppression of ionization in metastable neon traps due to long-range anisotropy

Cited by 24 publications

References 30 publications

Tensorial analysis of the long-range interaction between metastable alkaline-earth-metal atoms

Tensorial analysis of the long-range interaction between metastable alkaline-earth-metal atoms

Heteronuclear collisions between laser-cooled metastable neon atoms

Long-range interaction of two metastable rare-gas atoms

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