The positronium atom in the field of an optical laser: radiation-induced energy shifts and annihilation decay kinetics

摘要

A theory of quantum transitions in an atom of positronium is constructed that takes into account two-photon annihilation decay and optical transitions between two arbitrary states of the positronium atom. The problem is addressed without using perturbation theory by solving sixteen Heisenberg equations for the photon and atomic operators. Solutions to these equations are used to calculate radiative shifts of the energy levels of the positronium atom, phase relaxation times, and the lifetime of the positronium atom itself, taking into account spontaneous transitions and transitions stimulated optically between two quantum states. Radiative and nonradiative interactions of the positronium atom with die photon fields are distinguished. The role of coherent effects in positronium due to feedback from the fields of intrinsic and external photons is discussed. The kinetics of annihilation decay is investigated for various initial conditions. In addition, it is demonstrated that long-lived atoms of parapositronium can form in the field of an optical laser if one of the states of the positronium atom is a Rydberg state.