No abstract

Synthetic single crystals of CdS, CdSe, and CdTe have been produced by the reaction of cadmium vapor with H2S, H^Se, and HgTe, respectively, These "incomplete phosphors" show no phosphorescence but strongly developed photo-conductivity. Photo-cells made from these crystals are extremely sensitive in the whole region from the infra-red down to the ultraviolet, x-rays, and gamma-rays and for corpuscular rays, alpha-and beta-rays. Two different mechanisms of photo-conductivity occur. The normal photo-conductivity in the region of strong absorption from the blue to the ultraviolet, and the selective photo-conductivity in the region of weak absorption in the visible, x-rays, and corpuscular-rays region. The phenomena observed are in general accordance with the zonal theory of phosphorescence.

9 3 4 Der Starkeffekt der Lyrnnnserie V o n R u d o If F r e r i c h s (Mitteilung aus der Physik~isch-Technischen Reichsanstalt) (Mit 3 Figuren) ZusammenfaseungDer Starkeffekt der ersten drei Linien der Lymanserie wurde mit einem Vakuumspektrographen bestimmt. Zahl, L e e und Polarisation der beobachteten Komponenten stimmen mit der theoretischen Erwartung uberein. In den Intensitaten der Komponenten treten z. T. Abweichungen auf.

The CdS x-ray detector is compared with the photo-multiplier x-ray detector. Reduced to the same solid angle the sensitivity of the CdS x-ray detector is of the same order of magnitude as the sensitivity of the photo-multiplier x-ray detector. As the internal amplification of the primarily released electron currents in CdS is of the order 103 to 104 compared with the amplification in the multiplier tube of ½×106 the conversion process of x-ray quanta in slow electrons in CdS must be more efficient than the corresponding processes in the combination crystal phosphor screen photo-multiplier. Calibration curves show a linear relation between photo-current and intensity of x-rays at low irradiation levels. At high irradiation saturation effects occur. Oscilloscope curves of the response at 60 x-ray pulses per second are given. At strong irradiation the photo-current over a long time increases in a completely reversible way. X-ray intensities as low as 150 quanta CuKα per second are registered with a circuit employing a WL 759 trigger tube.

Artificial layered structures that produce sharp diffraction of x rays are described. The structures were made by alternately evaporating 140 Pb and Mg layers onto a glass slide (d=27 Å). The diffracting efficiency of the layered structures is compared with other structures used in soft x-ray spectroscopy. The usefulness of the structures is limited by diffusion in the layered system which caused the diffraction pattern to decay to half intensity in 2 days at room temperature. At 0°C the half life was 5 weeks. The diffusion model of DuMond and Youtz was used to determine an effective diffusion constant for the system over the temperature range 0–62°C. The equation Deff=5.2×10−6 exp(−20 600/RT) cm2/sec was satisfied.