Polarization correlations in the two–photon decay of hydrogen–like ions

摘要

Polarization properties of the photons emitted in the two–photon decay of hydrogen–like ions are studied within the framework of the density matrix and second-order perturbation theory. In particular, we derive the polarization correlation function that gives the probability of the (two–photon) coincidence measurement performed by polarization–sensitive detectors. Detailed calculations of this function are performed for the 2s _1/2 →1s _1/2 transition in neutral hydrogen as well as Xe53 + and U91 + ions. The obtained results allow us to understand the influence of relativistic and non–dipole effects on the polarization correlations in the bound–bound two–photon transitions in heavy ions.