On injective enumerability of recursively enumerable classes of cofinite sets

To date the problem of finding a general characterization of injective enumerability of recursively enumerable (r.e) classes of r.e. sets has proved intractable. This paper investigates the problem for r.e. classes of cofinite sets. We state a suitable criterion for r.e. classesC such that there is a boundn with |-A|n for allAC. On the other hand an example is constructed which shows that Lachlan's condition (F) does not imply injective enumerability for r.e. classes of cofinite sets. We also look at a certain embeddability property and show that it is equivalent with injective enumerability for certain classes of cofinite sets. At the end we present a reformulation of property (F).Thank you for technical support, Wolfgang Eppler, for intellectual support, Alistair Lachlan, and for proof-reading, Martin Kummer. Thanks also to the anonymous referee     

Energieverteilung der von 2, 5, 10 und 15 keV He- und Ar-Ionen an Molybdän ausgelösten Elektronen

The energy distribution of electrons ejected from Mo by He und Ar-ions of 2, 5, 10 and 15 keV has been measured by an electrostatic analyzer of the 127° cylindrical condenser type. The relative number of faster electrons grows with increasing primary energy, but the position of the maximum of the distribution curves (1.9 eV for He and 1.7 eV for Ar) is the same for ion energies of 5, 10 and 15 keV. Only for 2 keV the maximum is shifted slightly towards lower energies.     

Electron refraction and light polarization effects in angle-resolved photoemission spectra of Cu surfaces using 45 eV radiation

Angle-resolved photoemission spectra of the low Miller-index faces of copper were taken with polarized 45 eV light for both surface normal and off-normal photoemission orientations. They reveal that low-energy photoelectrons emitted off-normal to the surface are strongly refracted toward the surface at the solid-vacuum interface; measured refraction angles are significantly (5̃0%) larger than predicted from a simple plane wave model. Furthermore, the spectra are found to be very sensitive to the orientation of the polarization of the exciting radiation with respect to the crystalline axes and the sample surface. Spectral dependence on light polarization is discussed in terms of direct transition selection rules for primary Mahan cones, influence of directionality on matrix elements, and direct transition contributions to the spectra from surface photoemission.