The Schwarz-Hora effect: present-day situation

The electron-diffraction pattern at a nonfluorescent target was observed by Schwarz under attempts to modulate an electron beam by laser light. The pattern was of the same color as the laser light. The analysis of the literature shows there are the unresolved up to now significant contradictions between the theory and the Schwarz experiments. To resolve these contradictions, the interpretation of the Schwarz-Hora effect is considered, which is a development of the idea formulated by Schwarz and Hora. It is supposed that the interaction of electrons with the laser field inside a thin dielectric film is accompanied not only by the processes of absorption and stimulated emission of photons but also by formation of some metastable electron states in which the captured photons can be transferred with a following emission at the target.Comment: 5 pages, RevTex, 2 PS figure

Long beating wavelength in the Schwarz-Hora effect

Thirty years ago, H.Schwarz has attempted to modulate an electron beam with optical frequency. When a 50-keV electron beam crossed a thin crystalline dielectric film illuminated with laser light, electrons produced the electron-diffraction pattern not only at a fluorescent target but also at a nonfluorescent target. In the latter case the pattern was of the same color as the laser light (the Schwarz-Hora effect). This effect was discussed extensively in the early 1970s. However, since 1972 no reports on the results of further attempts to repeat those experiments in other groups have appeared, while the failures of the initial such attempts have been explained by Schwarz. The analysis of the literature shows there are several unresolved up to now contradictions between the theory and the Schwarz experiments. In this work we consider the interpretation of the long-wavelength spatial beating of the Schwarz-Hora radiation. A more accurate expression for the spatial period has been obtained, taking into account the mode structure of the laser field within the dielectric film. It is shown that the discrepancy of more than 10% between the experimental and theoretical results for the spatial period cannot be reduced by using the existing quantum models that consider a collimated electron beam.Comment: 3 pages, RevTe

Three Dimensional Acoustical Imaging Based on Isosurface Technique for Bulk Material

The paper introduces the methods with time-resolved technique and isosurface display technique to get two- and three-dimensional (3D) acoustical imaging for scanning acoustic microscopy. Time-resolved technique presents the way to realize two-dimensional (2D) acoustical imaging - A- (O-), B- and C-scan, and a discrete combinatorial 3D image; and isosurface display technique realizes a 3D image with continuous distribution in full direction. The paper proposals a transitional model of square column, which consists of the data of echo signal pattern extracted from volume database, to construct the imaging cube and depict an isosurface using isovalue of internal boundaries in the cube, for the evaluation of internal defects in bulk specimen - Boron Nitride. 3D acoustical imaging has the advantage to show the position, size, appearance, distribution, and tendency of internal structures (voids, inclusions and defects) with complex shapes in non-transparent bulk material. The results show that 3D acoustical visualization presents more affluent, overall and intuitive pattern than 2D imaging for micro-sized structure investigation