K. Pisk

Calculation of nuclear excitation in an electron transition

Abstract We have made a theoretical investigation of nuclear excitation during an electron transition (NEET). Our approach allows us to express the NEET probabilities in terms of the excited nuclear level width, the energy difference between the nuclear and electron transition, the Coulomb interaction between the initial electron states, and the electron level width. A comparison is made with the available experimental results.

Positronium interaction with low-energy radiation

The cross sections of elastic photon scattering, Compton scattering and photodisintegration for positronium are calculated for incident photon energies below 3 keV. The relation between positronium and hydrogen matrix elements for these processes is established and we compare our positronium cross section calculations with the corresponding hydrogenic data. We present the model for the positronium triplet state depletion before annihilation, when the positronium atoms are exposed to black-body radiation, and the breakup process occurs. We discuss the relevance of our breakup calculation for the positron annihilation process in solar flares.

Wave–particle duality of radiation in Compton scattering

In this work we analyze the wave–particle aspects of radiation in (incoherent) Compton scattering in the radiation energy range from 2–100 keV. From the calculated cross sections of the scattering from the electron (positron), hydrogen and positronium we construct the interpretation functions (IFs), where our assertion is that the Compton scattering from the free electron (positron) is an established example of the particle behavior of radiation. These IFs estimate the possibility of the interpretation of radiation in terms of waves or particles in an analogy with the analysis carried out in the coherent scattering of light. Based on these IFs we propose a new criterion for the estimation of the validity of the impulse approximation (IA).

Disintegration of positronium: Low energy Compton scattering and photoabsorption

We study interference effects in Compton scattering of a photon from positronium. Interference effects, which are due to the binding of an electron and a positron, are important at lower energies up to several keV. In our study we use full nonrelativistic electron/positron-photon interaction.

Interference effects in Compton scattering from positronium and from H2 and H2+ molecules

We study the interference effects in Compton scattering of a photon from positronium and from the simplest molecules H2 and H2+ in their ground states. We will discuss the adequacy of impulse approximation in describing these interference effects.