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We present new break-up and coherent data for h meson photoproduction on the deuteron, using a deuterium target and tagged bremsstrahlung photons up to 1 GeV. The differential cross sections for the coherent process were measured from threshold to 800 MeV. They are much smaller than those previously reported. The break-up channel provides a direct measurement of the neutron to proton differential cross section ratios. At the S 11 ͑1535͒ resonance peak, s n ͞s p 0.68 6 0.06 leading to an isoscalar to isovector amplitude ratio of A s ͞A y 0.096 6 0.02. [S0031-9007 (97)03324-3]

Differential cross-sections for quasi-free Compton scattering from the proton and neutron bound in the deuteron have been measured using the Glasgow/Mainz photon tagging spectrometer at the Mainz MAMI accelerator together with the Mainz 48 cm Ø × 64 cm NaI(Tl) photon detector and the Göttingen SENECA recoil detector. The data cover photon energies ranging from 200 MeV to 400 MeV at θ LAB γ = 136.2 • . Liquid deuterium and hydrogen targets allowed direct comparison of free and quasi-free scattering from the proton. The neutron detection efficiency of the SENECA detector was measured via the reaction p(γ, π + n). The "free" proton Compton scattering cross sections extracted from the bound proton data are in reasonable agreement with those for the free proton which gives confidence in the method to extract the differential cross section for free scattering from quasi-free data. Differential cross-sections on the free neutron have been extracted and the difference of the electromagnetic polarizabilities of the neutron has been determined to be αn − βn = 9.8 ± 3.6(stat) +2.1 −1.1 (syst) ± 2.2(model) in units of 10 −4 fm 3 . In combination with the polarizability sum αn + βn = 15.2 ± 0.5 deduced from photoabsorption data, the neutron electric and magnetic polarizabilities, αn = 12.5 ± 1.8(stat) +1.1 −0.6 (syst) ± 1.1(model) and βn = 2.7 ∓ 1.8(stat) +0.6 −1.1 (syst) ∓ 1.1(model) are obtained. The backward spin polarizability of the neutron was determined to be γ (n) π = (58.6 ± 4.0) × 10 −4 fm 4 . PACS. 13.60.Fz Compton scattering -14.20.Dh Protons and neutrons -25.20.Dc Photon absorption and scattering ⋆ Supported by Deutsche Forschungsgemeinschaft (SFB 201, SFB 443, Schwerpunktprogramm 1034 through contracts DFG-Wi1198 and DFG-Schu222), and by the German Russian exchange program 436 RUS 113/510.) a Part of the Doctoral Thesis b Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig c Part of the Doctoral Thesis d Part of the Habilitation Thesistomary to consider special properties of these amplitudes which have a transparent physical interpretation. These properties are given in terms of electromagnetic structure constants of which the E2/M1 ratio of the p → ∆ transition, the electric and magnetic polarizabilities α and β, respectively, and the spin polarizabilities γ 0 and γ π , for the forward and backward direction, respectively, are the most prominent.These electromagnetic structure constants have been studied for the proton for a long time, whereas the corresponding investigations for the neutron are only beginning. This contrasts with the fact that for their interpretation it is of great interest to know whether or not the proton and the neutron have the same or different electromagnetic structure constants. This is one reason to study the electromagnetic polarizabilities of the neutron in addition to those for the proton. Since Compton scattering

Tabulations are presented of relativistic Hartree-Fock-8later modified atomic form factors from x = ° to 100 A-I for all elements from Z = 1 to Z = 100. These modified form factors represent the atomic Rayleigh scattering amplitudes with good accuracy at energies well above theK-sheli binding energies and small momentum transfex:s and therefore should be used instead of the normal relativistic atomic form factors In the MeV energy range.

Using the Mainz 48 cm лϫ64 cm NaI͑Tl͒ detector and the segmented Göttingen recoil detector SENECA in coincidence, Compton scattering by the proton at ␥ lab ϭ136°has been measured at MAMI ͑Mainz͒ in the energy range from 200 to 470 MeV. The new data confirm the previous observation that there is a systematic discrepancy between MAMI and LEGS ͑Brookhaven͒ data leading to different spin polarizabilities ␥ ϭ Ϫ38.7Ϯ1.8 and Ϫ27.2Ϯ3.1 (ϫ10 Ϫ4 fm 4 ), respectively.