HYDROGEN-ANTIHYDROGEN INTERACTIONS

A small number of antihydrogen (AH) atoms have recently been prepared at CERN and at Fermilab. However, these atoms were travelling at speed s close to that of light. It is intended to carry out experiments on A H by trapping it at very low temperature (<1 K) in an inhomogeneous ma gnetic field. The main cause of loss of AW is due to collisions with H -2 and He with energies up to room temperature. However, these reactio ns are not easy to treat theoretically. In this paper we consider the interaction between AH and H. This has already received some attention . Initially, in a collision between AH and H the electron is bound to the proton and the positron is bound to the antiproton. Clearly, if th e proton and antiproton coincide they cannot bind the two light partic les. There exists a critical value, R-c, of the internuclear distance, probably not very much below a(0), below which the electron and the p ositron can attain a lower energy by separating from the nuclei and fo rming positronium. As a first stage in our work on the H-AH interactio n, we are carrying out variational calculations of the energy of the H -AH system for internuclear separations a short distance above R-c. Th e aim is to determine R-c as accurately as possible. The basis set use d is similar to that of a previous calculation by W. Kolos, D.L. Morga n, D.M. Schrader. L. Wolniewiez, Phys. Rev. A 11 (1975) 1792. However, it also contains a function to represent weakly bound positronium. In itial results suggest that R-c < 0.8a(0). (C) 1998 Elsevier Science B. V. All rights reserved.