Resonance states in the hydrogen-antihydrogen system from a nonadiabatic treatment

The quantum-mechanical four-body problem for the hydrogen-antihydrogen system has been solved by means of the variational implementation of the coupled-arrangement channel method. Wave functions have been formed using the Gaussian expansion method (GEM) in Jacobi coordinates; they explicitly include components corresponding to the rearrangement from hydrogen and antihydrogen (H + (H) over bar into protonium and positronium (Pn + Ps). We analyze the solutions belonging to the discretized spectrum of the four-body eigenvalue problem, searching for resonance states at energies just below the H-(H) over bar dissociation energy threshold by means of the stabilization method and complex scaling.