On the production of the positive antihydrogen ion ${{{\rm \bar{H}}}^{+}}$ via radiative attachment

Abstract

We provide an estimate of the cross section for the radiative attachment of a second positron into the state of the ion using Ohmura and Ohmura’s (1960 Phys. Rev. 118 154) effective range theory and the principle of detailed balance. The ion can potentially be created using interactions of positrons with trapped antihydrogen, and our analysis includes a discussion in which estimates of production rates are given. Motivations to produce include its potential use as an intermediary to cool antihydrogen to ultra-cold (sub-mK) temperatures for a variety of studies, including spectroscopy and probing the gravitational interaction of the anti-atom.

Closing in on the properties of antihydrogen

“…Such a beam could be used to investigateH scattering, and also to produce the antihydrogen positive ion,H + , (viaH-Ps collisions) as envisaged by GBAR. This ion is likely to be of fundamental interest in its own right, and the Ps route to production appears to be the most efficient way, since the rate of direct radiative capture of a positron by a trappedH atom is low [53]. Ā H beam may also find application in further searches for a possible electric charge of the anti-atom.…”

Formation of H¯+ via radiative attachment of e+ to Jacob1, Zhang2, Müller3 et al. 2020Phys. Rev. Research60120View full textAdd to dashboardCite

“…From the point of view of quantum electrodynamics, the processes of radiative attachment of an electron to an atom and of a positron to an antiatom are in essence identical and their consideration may be based on the same treatment(s). Besides, it is known that good results for the detachment of an electron from H − by photoabsorption (see, e.g., [21,22] and references therein) and by the impact of charged particles [26] as well as for radiative attachment of an electron to H [21,22] are obtained when these processes are treated as effectively single-electron processes in which the interaction between the "active" electron and the core of H − is described by a shortrange effective potential (although a more rigorous treatment [22] is expected to yield better results). It is obvious that the same can also be done for radiative attachment of a positron toH [21,22].…”

“…(Single-center) spontaneous radiative attachment of an electron to atomic hydrogen has been considered and is well known (see, e.g., [18][19][20][21][22] and references therein). The corresponding results can be straightforwardly applied also for the attachment of a positron to antihydrogen [21,22]. Therefore, in our discussion of the attachment mechanisms we take, as a reference, the spontaneous radiative attachment: e + +H →H + +hω k .…”

“…To our knowledge, the mechanisms (ii) and (iii) have been considered neither for the formation ofH + nor for (the closely related process of) the formation of H − . In contrast, the mechanism (i) was studied both for the (e − + H) and (e + +H) systems (see, e.g., [18][19][20][21][22] and references therein). In this paper it is regarded as the reference mechanism and is considered for the sake of completeness (and convenience).…”

Analytical Results for the Three-Body Radiative Attachment Rate Coefficient, with Application to the Positive Antihydrogen Ion H+

“…They intend to form the antihydrogen ion H + as an intermediate step because its net charge would allow for sympathetic cooling with a mixture of positively charged ions of ordinary matter such as Be + , and, after they are cooled, the extra positron would be stripped off prior to studies of the gravitational interaction of the anti-atom [12][13][14]. The authors of [15,16] calculated the cross section and rate coefficient for the radiative attachment of a second positron to create the H + ion, H (1s) + e + → H + 1s 2 1 S e +hω .…”