Fe 96−x Co x C 4 (x = 0, 10, 20, 30, 40 at. %) alloys were obtained by mechanical alloying of Fe, C and Co powders using high-energy milling. The structural and magnetic properties of the alloy system were analyzed by X-ray diffraction, Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and Mössbauer Spectrometry at room temperature. The X-ray diffraction patterns showed a BCC-FeCoC structure phase for all samples, as well as a lattice parameter that slightly decreases with Co content. The saturation magnetization and coercive field were analyzed as a function of Co content. The Mössbauer spectra were fitted with a hyperfine magnetic field distribution showing the ferromagnetic behavior and the disordered character of the samples. The mean hyperfine magnetic field remained nearly constant (358 T) with Co content.

Photoemission from colour centres in KCl, KI, CsCl, and CsBr has been measured for the first time in ultrahigh vacuum Torr). Photostimulated emission produced by electron irradiation of 1 to 12 keV in CsCI and CsBr exceeded the dose required for their creation,showing that a multiplicative process occurs. This satisfies the main requirement, i.e., to contemplate the construction of a low-level image detector competitive with existing tubes. The photoemission spectrum of CsCl a t room temperature shows structure in the F-band. Es wurde die Photoemission aus Farbzentren in KCl, KJ, CsCl und CsBr zum erstenmal im Ultrahochvakuum Torr) gemessen. Die lichtstimulierte Emission infolge von Elektroneneinstrahlung von 1 bis 12 keV in CsCl und CsBr iiberstieg die Dosis fur deren Erzeugung und zeigte, da13 ein multiplikativer Prozess vorliegt. Dies erfiillt die Hauptforderung, namlich die Konstruktion eines ,,low-Level"-Bilddetektors in Konkurrenz mit existierenden Rohren. Das Photoemissionspektrum von CsCl bei Zimmertemperatur zeigt eine Struktur der F-Bande.

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The photoemission of F-centers in RbCl is st,udied after electron bombardment up to 20 kV. When illuminating with L-band and F-band light, photoemission is produced in the first case only, indicating the emission of hot electrons. The dependence of the overall photoemission efficiency as a function of the energy of bombarding electrons is determined and justified with a simple model.On a Btudie la photoemission des centres F e n RbCl apres un bombardement avec des 616ctrons de 20 kV. Quand on illumine avec lumiere de la bande L a t de la bande F on ne produit photobmission que dans le premier cas, ce qui indique une &mission par des "616ctrons chauds" (hot electrons). On determine l'efficacit.6 globale de photoemission en fonction de 1'6nergie des blbctrons de bombardement, ce qui est aussi expliqu6 par une modele simple.