Naslov
New developments in the theory of Compton scattering

Autori
Surić, T. ; Florescu V. ; Chatterjee B. K. ; Roy S. C. ; , LaJohn L. A. ; Pratt R. H.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
21th International Conference on X-Ray and Inner Shell Processes

Mjesto i datum
Pariz, Francuska, 22.06.2008. - 27.06.2008

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
Compton scattering; bound electrons; inner shells; Compton profile; impulse approximation; relativistic impulse approximation; S-matrix

Sažetak
Compton scattering of a photon from bound electrons is often treated within impulse approximation (IA), which describes inelastic scattering from bound electrons in terms of scattering from free electrons. This is usually good for the Compton peak region but fails for soft outgoing photons. The standard theory was formalized by Eisenberger and Platzman (EP) [P. Eisenberger and P.M. Platzman, Phys. Rev. A 2, 415 (1970)] whose work also suggested why IA was better than expected for doubly differential cross sections (only outgoing photon is observed) but not for the triply differential cross sections (both outgoing photon and outgoing electron are observed). Relativistic version of IA were worked out by Ribberfors [R. Ribberfors, Phys. Rev. B 12, 2067 (1975)], while a full relativistic second order S-matrix treatment within independent particle approximation was developed by Bergstrom and Surić [T. Surić et al, Phys. Rev. Lett. 67, 189 (1991) ; P. Bergstrom et al, Phys. Rev. A 48, 1134 (1993)]. Newer developments in the theory of Compton scattering include: (1) Demonstration that the EP estimates of the validity of IA are misleading, although the qualitative conclusion remains unchanged ; IA is not to be understood as the first term in a standard series expansion. (2) The greater validity of IA for doubles than for the triples, which when integrated give doubles, is related to the existence of a sum rule, only valid for doubles. (3) The so-called "asymmetry" of a Compton profile is primarily to be understood as simply the shift of the peak position in the profile ; symmetric and anti-symmetric deviations from a shifted Compton profile are very small, except for high Z inner shells where further p.A effects come into play. (4) Most relativistic effects, except at low energies, are to be understood in terms of simple kinematic modifications of non-relativistic IA, plus using a relativistic charge density for high Z inner shell states ; these shift the peak and change its height.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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