Metastable compound states of an antiproton and a hydrogen atom

Abstract

The stability of antiproton-hydrogen compound states (pH) is investigated theoretically. ThepH compound state has decay channels of atomic electron detachment (→e − +pp) and hadronic pair (p-p) annihilation, and hence it cannot be permanently stable even if the dissociation channel (→p + H) is energetically closed. In this paper, information on the metastablepH states at energies below the dissociation limit is obtained by analyzing low-energy resonances in e − +pp scattering. The scattering calculation is carried out by using an R-matrix method, which also allows for the annihilation channel simultaneously. The metastable states are found to be identified as vibrational levels supported by a Born-Oppenheimer (BO) potential. The energy-level widths attributed to the electron detachment and the annihilation are also calculated using a model based on the BO picture.

Exotic molecules consisting of an antiproton and a hydrogen atom

“…Also in thep + H system, the BO approximation works accurately except at small distances [26][27][28][29][30], and the polarization interaction, which has a range much longer than the dispersion interaction, was expected to be favorable for the bonding. However, thepH molecule was again found to be unstable due to electron detachmentpH →pp + e [25]. The same conclusion can be drawn also for the stability of the charge conjugation system pH.…”

“…excludes the possibility of the vibrational motion for all J . Actually in a rigorous calculation, any stable and even metastable vibrational states with high J could not be found [25]. A peculiar case is very high vibration just below the dissociation limit for J ∼ 0 [25].…”

“…Actually in a rigorous calculation, any stable and even metastable vibrational states with high J could not be found [25]. A peculiar case is very high vibration just below the dissociation limit for J ∼ 0 [25]. In this case, although the electron detachment and pair annihilation occur at small distances, the vibrational wave function can still have finite amplitudes even up to very large distances R ∼ 100 a.u.…”

“…Unfortunately, thē HH molecule was found to be always highly unstable due to the rapid rearrangement decay [19,[22][23][24]. As a similar subject, the stability ofpH molecular anions was examined [25]. Also in thep + H system, the BO approximation works accurately except at small distances [26][27][28][29][30], and the polarization interaction, which has a range much longer than the dispersion interaction, was expected to be favorable for the bonding.…”

“…ThepH system considered in Ref. [25] was assumed to be in the electronic ground state. If the H atom is electronically excited, the BO potential ofp + H can have asymptotically a long-range term proportional to 1/R 2 , with R being the relative distance [29,31,32].…”