Photon polarization in the two-photon decay of heavy hydrogen-like ions

Abstract

Abstract. We have applied the density matrix and second-order perturbation theory in order to re-analyze the two-photon decay of hydrogen-like ions for the polarization of emitted light. Special attention is paid to the linear polarization of one of the photons, while the spin state of the second photon is supposed to be unobserved. For such an "angle-polarization" correlation of the two photons we investigate the contributions that arise from non electric-dipole terms in the expansion of the electron-photon interaction. Detailed calculations are performed for the 2s 1/2 → 1s 1/2 and 3d 5/2 → 1s 1/2 transitions in neutral hydrogen as well as in hydrogen-like uranium.

Negative-continuum effects on the two-photon decay rates of hydrogenlike ions

“…In such strong fields produced by heavy nuclei, relativistic and retardation effects become of paramount importance and may strongly affect the properties of two-photon emission. To explore these effects, therefore, theoretical investigations based on Dirac's equation have been carried for the total and energy-differential decay rates [17,18,19,20,21] as well as for the angular and polarization correlations [22,23,24]. In general, relativistic predictions for the two-photon total and differential properties have been found in a good agreement with experimental data obtained for the decay of inner-shell vacancies of heavy neutral atoms [25,26] and excited states of high-Z fewelectron ions [27].…”

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

“…In this section we shall analyze the angular and polarization correlations defined in Eqs. (15) and (16), for decays of hyperfine 2s states in Hydrogen atom as well as in hydrogenlike Uranium ion.…”

“…Equipped with equations (15) and (16), in the next section we shall investigate the functions W χ1 χ2 (θ) and W (θ) as obtained for a few decays of unpolarized hyperfine 2s states in Hydrogen atom and in hydrogenlike Uranium ion.…”

Approximate Atomic Green Functions

“…Various non-linear (second- as well as higher-order perturbation) processes have been observed during the past years but could often not be calculated in good detail for many ions, atoms or molecules of interest. Well-known second-order processes of this sort include, for instance, the multi-photon absorption and emission [ 1 , 2 , 3 ], the resonant [ 4 ] and two-photon ionization [ 5 , 6 ], the radiative and double Auger emission of atoms [ 7 , 8 ] and molecules [ 9 ], their (single-photon) double ionization [ 10 , 11 , 12 ] or the Rayleigh and Raman scattering of light [ 13 , 14 , 15 ], to name just a few. Until the present, however, most of these processes are not yet (well) understood quantitatively since, in perturbation theory, each additional order (beyond the first-order) typically requires an implicit summation (integration) over the full spectrum of the system.…”