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The fine structure just above the L2,3 edge of aluminum at 72.72 eV has been examined with high resolution using the radiation of the Frascati electron synchrotron. A sensitive system providing normalization between the incident and transmitted light has allowed detection of absorption peaks not previously recorded in other measurements. It has been found that the optical response of the Al at these energies is strongly influenced by the oxide grown on its surface, so that corrections for the absorption of the oxide are necessary to yield only spectral features intrinsic to the metal. The results indicate that most of the fine structure of the L absorption spectrum is directly related to structure in the density of conduction-band states above the Fermi level.

The oscillations of two helium baths coupled by the saturated film have been studied with a new method employing positive ions. The sensitivity of such a method for the variation of liquid-level height is found to be of the order of 10−6 cm. The film current was observed to be modulated with a frequency double that of the level oscillations. This interesting new feature is discussed in the framework of the present theory of liquid helium.

Air entrained within enclosed inclined chutes conveying solid materials may contribute, unless exhausted, to the dispersion of dust in work areas. Quantities of air induced calculated from equations developed from the dynamics of free-falling particles do not often compare well with field measurements. A modified form of the theoretical equation including an efficiency factor derived from the geometry of the chute system gives fairly good agreement between computed and observed rates of air flow. A nomogram solution is given to aid the engineer in determining where exhaust will be required and what volume need be exhausted to achieve dust control.

The curves of error for dust counts were developed for counts made by aerosol photometer, midget impinger, and membrane filter procedures. The interrelation of counts by different procedures were studied. With limestone dust, the counts by the aerosol photometer were most reproducible and those by midget impinger were least reproducible. The type of dust and the particle size affected the comparability of counts by the different procedures.

The soft-X-ray spectra of aluminium oxide in the polycrystalline γ and amorphous forms have been investigated in detail with improved resolution using the synchrotron radiation of the Frascati electron synchrotron. In contrast to a previous measurement, it is found that the L2,3 threshold starts at almost the same energy in both forms. The sharp peaks observed at the absorption edge are interpreted as excitons. This picture fits well both with ESCA results and with the optical spectra at the fundamental edge in the ultraviolet. It is suggested that metastable excitons are responsible for the intense structure observed at (82.6 ± 0.3) eV in the ordered phase and lacking in the amorphous phase. The spectral features of crystalline alumina are analyzed on the basis of the band structure. The modifications induced by the lack of long-range order in the amorphous samples are discussed thoroughly. Kous avons etudie en detail les spectres d'absorption X de l'oxyde d'aluminium dans les formes polycristalline γ et amorphe avec meilleur resolution qu'auparavant, employant la radiation emise par l'electrosynchrotron de Fraseati. On a trouve, e la difference des mesures precedentes, que les transitions L2,3 commencent presque a la měme energie dans les deux formes. Le pics etroits observes on ete interprete commes des excitons. Cette interpretation s'accorde soit avec les resultats d'ESCA soit avec les spectres optiques pres de l'absorption fondamentale dans l'ultraviolet. On pense que des excitons metastables peuvent expliquer les structures observes a (82,6 ± 0,3) eV dans la phase ordonnee et manquantes dans la phase amorphe. Les spectres de l'alumine cristalline sont examinees suivant la structure des bandes. Les modifications dues a l'absence d'ordre cristallin a grandes distances dans les substances amorphes sont discutees.

The reflectivity of KCl has been measured up to 45 eV with synchrotron radiation extending the range of previous measurements. The absorption coefficient is compared with an ab initio calculation using an orthogonalized-plane-wave expansion for the final states of the excited electron and including excitonic and crystalline effects. The distribution of the oscillator strength and its modulations are well reproduced by the theory.