Exotic molecules consisting of an antiproton and a hydrogen atom

Abstract

A theoretical study is conducted on the stability of exotic antiproton-hydrogen molecular anions (pH), which in the separated atom limit correlate withp + H(n = 2) (n being the principal quantum number). Thē pH molecule in the electronic ground state is highly unstable due to pair annihilation and autodetachment (→pp + e). However, if thepH molecule is electronically excited, the molecular stability can be drastically improved. Since the excited states of the H atom have accidental degeneracy, the asymptotic form of the Born-Oppenheimer potential curve ofp + H(n = 2) behaves as 1/R 2 (R being the relative distance), which can play a critical role in the bonding and stability of the molecule. It is found that thepH molecule in the first electronic excited state and in a high rotational state is sufficiently stable and has a lifetime dominated by spontaneous radiative emission (→p + H + hν). ThepH system is dynamically similar to H 2 − , which had been commonly considered to be unstable due to autodetachment. However, recent measurements of ion-beam sputtering unambiguously verified the existence of long-lived H 2 − molecules in high rotational states. This suggests that thepH molecules may actually be created if one employs experimental means such as the chemical sputtering of hydrogen-rich targets withp beams.

Quasibound states of an antiproton and a hydrogen atom

“…This is provided by the Born-Oppenheimer results of Ref. [14]. They suggest the existence of quasibound states or narrow resonances in the domain 59 ≤ L ≤ 73.…”

“…According to Ref. [14], p + H dissociation is the main separation process. This is confirmed by the mean values of the distances between particles shown below.…”

“…In a study based on the Born-Oppenheimer approximation, Sakimoto has deduced that the binding of an antiproton by an hydrogen atom in its ground state is unlikely [13]. In a further work, however, he has shown that this binding could be possible at very high angular momenta when the hydrogen atom is in its first excited Stark-like state [14]. The reason is that the antiproton-hydrogen Born-Oppenheimer potential then has a much slower decrease than for hydrogen in its ground state and can be attractive enough at large distances.…”

Levels of Composition: from Quarks to HHe+ Molecular Ion

“…HeH + is included here. An exotic molecule contains one or more exotic atoms, such as positronium hydride (a positronium atom bound to a hydrogen atom) and di-positronium (two bound positronium atoms) [79] . Molecules that will be synthesized during or after the Recombination epoch are listed here also (as isolated systems) [80][81][82] .…”

Pulsed production of cold protonium in Penning traps

“…This has been recently studied in CTMC simulations ofp collisions with H(2s) and Ps(2s) in Ref. [35,36], and with Ps(n 8) in Ref. [37], and Pn(n 50) in Ref.…”