Delbruck and Rayleigh scattering by uranium investigated at photon energies between 0.1 qnd 1.5 MeV

Validating polarization effects in γ-rays elastic scattering by Monte Carlo simulation

“…However, at  120 , the inclusion of Delbrück amplitudes reduces the polarization of the scattered photon by a factor of 3. Despite the lack of experimental measurements of polarization at this energy and scattering angle, the role of Delbrück amplitudes at 1.33 MeV is consistent with measurements of the differential cross section of elastic scattering of 1.33 MeV by uranium provided by Muckenheim and Schumacher [31]. In general, the elastic scattering of photons is a phase-dependent process, which means the contributing amplitudes must be added coherently before squaring.…”

Nuclear photoexcitation and delbr�ck scattering studied in the energy range 2?8 MeV

“…At these low energies the use of radioactive sources has a great advantage over (n,7)-sources because of the much lower background. Details of the experimental procedure and the evaluation of the data have been described elsewhere [5,13,14].…”

“…At low energies (2-4 MeV) the photons were supplied by radioactive sources, at high energies (4)(5)(6)(7)(8) by neutron capture sources. The present energy resolution amounts to typically 30 to 80 eV, which is 3 to 4 orders of magnitude better than that achieved in experiments carried out with "tagged" bremsstrahlung photons [1].…”

Relativistic oscillator model and Delbrück scattering

“…Elastic scattering of photons in the Coulomb field of nuclei via virtual electronpositron pairs (Delbrück scattering [1]) attracted considerable interest for a long time. That is motivated by two reasons: (i) The Delbrück scattering is one of a few nonlinear quantum-electrodynamic processes which can be precisely tested by experiment [2,3,4,5]. (ii) In order to extract an information on nuclear structure from differential cross sections of photon scattering on nuclei, a precise knowledge of the Delbrück amplitude may be required because of its interference with the nuclear amplitude.…”

“…In case of the oscillator potential U(r), the Klein-Gordon operator has only a discrete spectrum (3) and therefore the Green function has only simple poles at real ǫ = ±(E n − i0) displaced by i0 in accordance with the Feynman rules. Using this analytic property, we can deform the integration path over ǫ in (5), ǫ → iǫ, to make it finally coincident with the imaginary axis. As a result, we get a possibility to rotate the contour of integration over s in ( 6)-( 8), s → −is, to make all the integrals well-convergent.…”