Parametrization of the angular correlation and degree of linear polarization in two-photon decays of hydrogenlike ions

摘要

The spontaneous two-photon emission in hydrogenlike ions is investigated within the framework of secondordernperturbation theory and Dirac’s equation. Special attention is paid to the angular correlation of the emittednphotons as well as to the degree of linear polarization of one of the two photons, if the second is just observednunder arbitrary angles. Expressions for the angular correlation and the degree of linear polarization are expandednin powers of cosine functions of the two-photon opening angle, whose coefficients depend on the atomic numbernand the energy sharing of the emitted photons. The effects of including higher (electric and magnetic) multipolesnupon the emitted photon pairs beyond the electric-dipole approximation are also discussed. Calculations of thencoefficients are performed for the transitions 2s1/2 → 1s1/2, 3d3/2 → 1s1/2, and 3d5/2 → 1s1/2, along the entirenhydrogen isoelectronic sequence (1 u0002 Z u0002 100).