Primjenljivost Comptonovog raspršenja za određivanje impulsne raspodjele elektrona

We present new insights regarding the validity of the impulse approximation (IA) in determining electron momentum density (EMD) from Compton scattering. These insights are obtained utilizing the code we have recently developed for the full calculation of the triple differential cross-section (TDCS) for Compton scattering. We find that, due to the averaging, at lower energies IA is more accurate for the double differential cross-section (DDCS) than for TDCS. We conclude that at such energies an EMD determination from the DDCS is more accurate than its direct determination through the measurement of the TDCS at the same energy. We also discuss the validity of IA for calculations of other less averaged Compton observables.Predstavljamo nove poglede o valjanosti impulsne aproksimacije (IA) za određivanje impulsne raspodjele elektrona (EMD) Comptonovim raspršenjem. Ti se pogledi osnivaju na primjeni nedavno razvijenog programa za računanje trostrukog diferencijalnog udarnog presjeka (TDCS) za Comptonovo raspršenje. Nalazimo da zbog računanja prosjeka, IA je na niskim energijama točnija za dvostruke diferencijalne presjeke (DDCS) nego za TDCS. Zaključujemo kako je na tim energijama određivanje EMD na osnovi DDCS točnije nego mjerenjem TDCS na istoj energiji. Raspravljamo također valjanost IA za određivanje drugih Comptonovih manje usrednjenih veličina

Nuclear excitation by the inelastic photoelectric effect

The possibility of a nucleus being excited during an interaction involving an incident photon, a bound orbital electron, and the nucleus has been investigated. In this inelastic photoelectric effect the angular distribution of the ejected photoelectrons has been calculated and the dependence of the total cross section on the photon energy and the nuclear excitation energy has been investigated. NUCLEAR REACTIONS Calculated probability of nuclear excitation in interaction involving incident photon and bound atomic electron. Dependence of cr on Z, E~, and photoelectron emission angle 8 studied

Perturbative calculation of the cross section in double ionization by high-energy Compton scattering

In this paper we investigate double ionization in high-energy Compton scattering from the He-atom including both the shake-off mechanism and a perturbative correction to that mechanism. The correction is calculated in second-order perturbation theory and includes Coulomb electron-electron interaction in addition to the correlation in the ground state of the He-atom. Our calculations for the ratio of double to single cross section cover the range from 30 to 300 keV of impact photon energy and explain the slow convergence of the ratio towards the asymptotic value

The Persistent Correlation Effects in Double Ionization of Helium-Like Atoms Or Ions Which Are Probed With High Energy Photons

We analyze the correlation effects in two electron atoms and ions which can be probed in double ionization with high energy photons. We consider total cross sections and differential cross sections for double ionization by photoabsorption and Compton scattering and discuss the shake and non--shake mechanisms which may contribute to these observables. The total cross section for photoabsorption (at high energies) is determined by two mechanisms, the shake--off mechanism and a quasi--equal--energy sharing mechanism, while for Compton scattering it is determined by the shake--off mechanism. In general the shake--off mechanism probes different distances in the two processes, so that the shake--off ratios are different. Analyzing differential cross sections, we are able to distinguish the shake from the non--shake contributions in photoabsorption, or the variation of shake--off result with distance probed in Compton scattering. We discuss the utilization of the double ionization Compton pro..

Scattering of Photons From Atomic Electrons

Validity of simpler approaches for elastic and inelastic photon scattering by atoms and ions is assessed by comparison with second-order S-matrix predictions. A simple scheme for elastic scattering based on angle-independent anomalous scattering factors has been found to give useful predictions near and below photoeffect thresholds. In inelastic scattering, major deviations are found from A{sup 2}-based calculations. Extension of free-atom and free-ion cross sections to the dense plasma regime is discussed. 20 refs., 6 figs