Page - 138 - in The Vienna Genesis - Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment

138 The silver inks of the Vienna Genesis The analysis of crystalline phases by X-rays as a probe is based on the physical principle of the diffraction of individual electromagnetic waves, which arises by the scattering process at the individual electrons within atoms during the interaction of the sample with the X-ray radiation. The X-ray wavelengths used for these types of experiments are within the range of 0.05 < λ < 0.3 nm and thereby correspond to the range of inter-atomic distances in crystals. Together with a strict long-range order of atoms present in the crystallites, i. e. periodicity, the latter is subject to the observation of a diffraction spot on a detector. The diffraction angle yields the information of the lattice parameters and bond lengths based on the lattice plane distances. The intensity implies the amplitude of the resulting wave after the diffraction at the atomic arrangement and therefore contains the information on the atomic type and position within the arrangement. Both parameters are structure phase intrinsic and can be considered as a fingerprint for a phase present within a sample45. The qualitative analysis of the crystallographic phases was done by comparison of the observed intensity and positions of detected reflections to either crystalline phases in the data base or to theoretical positions from structure modelling using the PDF-4+ data- 45 Bragg and Bragg, 1913, pp. 428–438. Fig. 21: Scanning electron microscope image of sample T1 from the Vienna Genesis. The red ellipse represents the size of the µm–beam, the blue and green rectangles the areas of mainly parch- ment (blue) and ink/corrosion (green). Open-Access-Publikation im Sinne der CC-Lizenz BY 4.0