Showing papers by "Fraunhofer Society published in 1979"

Optical and ESR spectroscopy of deep defects in III-V semiconductors

Abstract: A survey of recent progress on the assessment of deep defects in GaP, GaAs and, InP by electron spin resonance (ESR) and optical spectroscopy is presented. The stoichiometric defects sofar identified by ESR, the antisite center PGa, and the isolated gallium vacancy are treated in detail. The present understanding of the deep states introduced by oxygen in GaP is reviewed. Besides oxygen the most common, inadvertent deep impurities in III-V compounds are the 3d-transition elements. Their ESR and optical spectra will be discussed, also in connection with their often deleterious influence on device performance.

Influences Of Solar Activity On The Electric Potential Between The Ionosphere And The Earth

Abstract: Since 1954, we recorded the electric field E, air earth current density I, and additional electric and meteorological parameters on a high mountain top station (3 km). In 1960 we were able to show that E and I rise simultaneously and significantly 2 to 4 days after solar flares, but only if recorded on genuine fair weather days above the mixing layer. A carefully elaborated sequence of data is available from 1964 to 1975, i.e., a period of 12 yr. It shows that 1 to 2 days after sector structure boundary passages of the IMF, type −/+, E and I rise quite significantly by 20 to 30% (fair weather, above the mixing layer). During passages of the type +/−, the reaction of E and I is somewhat weaker (15%); the maximum is found precisely on the day of the passage. The in phase variation of E and I above the mixing layer is representative of the electric potential of the ionosphere.

New results regarding the influence of solar activity on the stratospheric-tropospheric exchange

Abstract: The dependence of stratospheric intrusions on solar events is analyzed on the basis of 8-years' recordings of the concentration of stratospheric radionuclides and the ozone at 3 km altitude, as well as of the atmospheric profile of the ozone concentration and the total ozone.

High-intensity brillouin scattering from parametrically excited phonons in FeBO 3

Abstract: The saturation of the ferromagnetic resonance in FeBO3 is due to the parametric decay into short wavelength phonons of half the exciting frequency. These phonons are observed using the technique of inelastic light scattering. Their intensity is so high (105 above thermal level) that the scattered light can be observed visually. Light scattering and parametric decay selection rules result in well defined scattering angles. The analysis of these directions allows the evaluation of anisotropic sound velocities.

Influences of Solar Activity on the Exchange Intensity Between Stratosphere and Troposphere

Abstract: Recordings of Be7 and O3 in the air from a mountain observatory (3 km altitude, Zugspitze) constitute the basis for a study of the question whether the frequency of intrusions of stratospheric air into the troposphere is influenced by solar events. An influx of stratospheric air passing the measuring station is indicated by a noticeable increase in the concentration of these stratospheric constituents. Since 1973 we have been able to identify a 40% increase in the frequency of stratospheric intrusions 2 to 3 days after solar flares and sector structure boundary passages. Recent studies aimed at a physical interpretation revealed a close correlation between stratospheric intrusions triggered by solar action and the Forbush effect. Recently, it has become possible to show that the intrusions are also coupled with an increase in the O3 concentration in the stratosphere, mainly in its lower layers.