Formation of H¯+ via radiative attachment of e+ to

Abstract

We consider the formation of positive ions of antihydrogenH + via radiative attachment of incident positrons e + to antihydrogen atomsH. The formation mechanisms include (i) spontaneous radiative attachment in which the ion is formed due to spontaneous emission of a photon by a positron incident onH; (ii) induced radiative attachment where the formation proceeds in the presence of a laser field via induced photoemission; and (iii) two-center attachment which takes place in the presence of a neighboring atom B and in which an incident positron is attached toH via resonant transfer of energy to B with its subsequent relaxation through spontaneous radiative decay. We show that the mechanisms (ii) and (iii) can strongly dominate over the known mechanism (i). Besides, according to our estimates, in the range of positron energies ( 1 eV) where the radiative channels are most efficient, the mechanism of (nonradiative) three-body attachment, in which one of two positrons incident onH forms the ion whereas the other one carries away the energy excess, is much weaker than the channel (i). We also briefly discuss three-body attachment where, instead of two positrons, a positron and an electron are incident onH.

Formation of $\bar{\rm{H}}^+$ via three body attachment of $\rm{e}^+$ to $\bar{\rm{H}}$

“…For the derivation of the rate (15), we only have taken into account contributions to 2CDA from distant collisions where b min 1 a.u. [16,27]. Thus, the result (15) represent a lower boundary for the 2CDA formation rate.…”

“…In [16] we have considered two-center dileptonic attachment (2CDA) of a positron to H which may occur when positrons and antihydrogen move in a (dilute) gas of atomic species B: e + + H+B → H+ +B * → H+ +B+ ω k . If the energy release ω A = ε kp − ε g in the positron attachment is close to an excitation energy ω B of a dipole transition in B, then the energy excess can be efficiently transferred, via the two-center positron-electron interaction, to B which, in consequence, undergoes a transition into an excited state.…”

“…From the consideration in [16], we obtain the H+ formation rate R 2CDA per unit of time (per H) for 2CDA which is given by…”

“…Therefore, the efficiency of the two-center attachment is limited to low velocity collisions, in which the velocity v of H with respect to B is much less than 1 a.u. [16,27].…”

“…In a recent study [16], we have focused on the formation of the H+ ion via radiative attachment of a positron to H in which the energy release is carried away by emission of a photon. Among the processes considered were spontaneous radiative attachment where H+ is formed due to spontaneous emission of a photon by a positron incident on H and two-center dileptonic attachment which becomes possible in the presence of a neighboring (matter) atom B and in which an incident positron attaches to H via resonant transfer of excess energy to B driven by the two-center dileptonic interaction with subsequent stabilization of B via spontaneous radiative decay.…”