Zur Elektronennachemission bei Ionenkristallen

The emission of electrons from NaCl-, LiF- and Zn-crystals after excitation by electrons and α-particles was investigated. The influence of external electrical fields on the emission was studied. The results of this investigations are compatible with the model developped byMatyás according to which an electrical dipole-layer is caused by the distribution of lattice defects in the surface.     

Elektronenemissionen und Farbzentren bei Ionenkristallen

Zusammenfassung Es werden weitere Erkenntnisse über die Elektronenemission aus verschiedenartig gefärbten Ionenkristallen angeführt und die näheren Zusammenhänge zwischen den Farbzentren und einigen physikalischen Erscheinungen besprochen, wie z. B. dem äusseren Photoeffekt, der Thermolumineszenz und der aktivierten Adsorption.     

Theorie der Multipolrelaxation

The multipole resonance and relaxation is discussed starting with a general consideration of the quantum mechanical dynamics of spinsystems with arbitrary spinI. The irreversible entropy production as a function of the multipolarisations is calculated from the density operator, expanded in terms of a complete set of orthonormal multipole operators. By use of the methods of thermodynamics of irreversible processes one obtains relaxation equations, which are a generalization of the Bloch equations of pure magnetic dipole relaxation. They connect the time derivatives of the multipolarisations with affinities, which are defined by the expansion of the logarithmus of the density operator; for small multipolarisations the affinities are equal to the multipolarisations themselves. Relations for the relaxation matrix are discussed, especially a derivation is given for reciprocal relations between the relaxation coefficients. In the special case of spinI=1 the equations of quadrupole relaxation are studied for axial symmetry.     

Die Spektren der Photoneutronen aus O18 und N14

Water enriched to 97% in O¹⁸ and liquid nitrogen were irradiated with 30,5 MeV bremsstrahlung. The energy distribution of emitted neutrons between 2,5 MeV and 20 MeV was measured via the recoil protons in a stilbene scintillator. The energy spectrum of photoneutrons from N¹⁴ shows maxima at 3,0, 6,5 and 11 MeV, whereas that of neutrons from O¹⁸ contains only indication of structure. For both nuclei emission of neutrons seems to proceed mainly through transitions into excited levels of the final nuclei.