Formation of triplet positron-helium bound state by stripping of positronium atoms in collision with ground state helium

The system consisting of a positron and a helium atom in the triplet state e$^{+}$He($^{3}$S$^{e})$ was conjectured long ago to be stable [1]. Its stability has recently been established rigorously [2], and the values of the energies of dissociation into the ground states of Ps and He$^{+}$ have also been reported [3] and [4]. We have evaluated the cross-section for this system formed by radiative attachment of a positron in triplet He state and found it to be small [5]. The mechanism of production suggested here should result in a larger cross-section (of atomic size) which we are determining using the Born approximation with simplified initial and final wave functions. [1] R. J. Drachman, Y. K. Ho, and S. K. Houston, J. Phys B \textbf{9}, L199 (1976) [2] G.G. Ryzhikh and J. Mitroy, J. Phys. B \textbf{31} 3465 (1998) [3] A. M. Frolov, Phys. Rev. A. \textbf{71} 032506 (2005) [4] J. Mitroy, Phys. Rev. A. \textbf{72 }032503 (2005) [5] J. Di Rienzi and R. J. Drachman, Phys. Rev A \textbf{73}, 012703 (2006)