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Publication Type: search.filters.UBSTyp.KonferenzbeitragSubject: search.filters.subject.530Institute: search.filters.UBSInstitut.Sonstige EinrichtungStart date: 1976End date: 1979

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Now showing 1 - 5 of 5
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    Resonance and relaxation attenuation by neutral acceptors in a magnetic field
    (1977) Schad, Hanspeter; Lassmann, Kurt; Zeile, Heinrich
    Fine structure, level splitting, and relaxation times of the acceptor ground state in cubic semiconductors can be deduced from ultrasonic attenuation. By the application of a magnetic field it is possible to vary the coupling strength and the number of acceptors on speaking terms with the ultrasonic wave. Making use of this possibility, we have determined directly effective coupling constants for relaxation attenuation and the temperature dependence of the critical intensity for saturation of the resonant interaction. Results obtained for p-type GaAs and Si are discussed in comparison with analogous results for glasses.
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    ODMR of phanes and charge transfer phanes
    (1979) Schweitzer, Dieter; Goldacker, Wilfried; Hausser, Karl H.; Staab, Heinz A.
    Triplet zero field splitted parameters |D| and |E| and decay rates ki of the triplet sublevels of two stereoisomeric tetramethoxy [2.2] paracyclophanes as well as those of two CT [2.2] paracyclophanes in low concentration in glasses and small neat single ctystals as measured by ODMR in zero fields at 1,3 K are presented.
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    Phonon scattering due to deep acceptors in semiconductors
    (1976) Combarieu, Andre de; Lassmann, Kurt
    We have measured the magnetothermal conductivity in GaAs(Mn) and Si(In) for temperatures between 1.4 K and 90 K at magnetic fields up to 8 T. In both cases the dopants are deep acceptors with binding energy much larger (110 meV and 165 meV respectively) than given by the effective mass theory (~ 35 meV). There is a double interest in such systems: First, an excited level 3 meV (4.2 meV) above the acceptor ground state has been concluded from ultrasonic measurements. Such an excited state might be connected with a Jahn-Teller effect of these deeper acceptors and should be seen by resonant phonon scattering in thermal conductivity. Second, an anomalous behavior of the magnetothermal conductivity has been found for shallowacceptors in Ge (but not in Si) making comparison with systems with different g-factors desirable. The g-factors of acceptors in GaAs are roughly three times, the g-factor of Si(In) about 0.6 times that of Si(B).
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    Image quality criteria for aerial survey lenses
    (1978) Tiziani, Hans J.
    An image quality criterion based on MTF is highly desirable. The quality specification should be appropriate for the application of the optical system and simple for the user. The proposed quality criteria look promising and comparisons with subjective image quality techniques commonly used are favourable. Further evaluations are needed before quality specification can be recommended.
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    A review of speckle photography and interferometry
    (1977) Tiziani, Hans J.
    Laser photography has been found to be a very useful and powerful tool for many applications. The interpretation of the fringes obtained is very much easier than for holography. Speckle techniques for strain, displacement and vibration analysis were found to be very powerful aids. The requirements on coherence of the light source used are moderate. High-resolution, low-scatter film or plates can be used to record the speckle patterns (Kodak or Agfa Scientia).