Cold neutral atoms via charge exchange from excited state positronium: a proposal

Abstract

We present a method for generating cold neutral atoms via charge exchange reactions between trapped ions and Rydberg positronium. The high charge exchange reaction cross section leads to efficient neutralisation of the ions and since the positronium-ion mass ratio is small, the neutrals do not gain appreciable kinetic energy in the process. When the original ions are cold the reaction produces neutrals that can be trapped or further manipulated with electromagnetic fields. Because a wide range of species can be targeted we envisage that our scheme may enable experiments at low temperature that have been hitherto intractable due to a lack of cooling methods. We present an estimate for achievable temperatures, neutral number and density in an experiment where the neutrals are formed at a milli-Kelvin temperature from either directly or sympathetically cooled ions confined on an ion chip. The neutrals may then be confined by their magnetic moment in a co-located magnetic minimum well also formed on the chip. We discuss general experimental requirements.

Antihydrogen formation in low-energy antiproton collisions with excited-state positronium atoms

“…Indeed, the cross sections, as elucidated in [27], and described briefly in section 2, rise as n 2 i , which is also depressed in comparison to the n 4 i classical expectation. The results are of relevance forH experiments planning to use reaction (1) (e.g., [19][20][21][22]), and possibly other applications involving charge exchange in Ps collisions with ionic species [47]. Some of these initiatives intend to use Rydberg Ps (say species with n i = 10 or above), and the present work must cast doubt on estimates used to assess experimental feasibility.…”

Experimental progress in positronium laser physics

“…Similarly, one could use He + ions (which are even easier to produce than protons [434]) to measure charge-exchange neutralization following Rydberg Ps collisions with the ions. A related scheme has recently been proposed to produce cold atoms following ion cooling in a neutral atom trap superimposed over an electrostatic ion trap [435].…”

“…As an extension, the Rydberg atoms themselves could be used as surface probes via resonant charge transfer processes [426,427]. Neutralization of laser cooled ions in Penning or Paul traps has also been suggested as a method to produce cold atoms or molecules that are not amenable to laser cooling [435].…”

Multiring electrostatic guide for Rydberg positronium

“…Indeed, with the addition of extended electrodes simulations suggest that a stronger focusing effect is possible if time-varying fields are used to account for the different Ps velocities [61]. This could be useful in experiments in which Ps atoms interact with other species in order to study scattering or charge exchange mechanisms [62][63][64]. We note that it is difficult to characterize the overall efficiency and acceptance of the guide because we do not accurately know the initial phase-space properties of the Ps atoms.…”