Universität Stuttgart
Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1
Browse
9 results
Search Results
Item Open Access Die optische Ühertragungsfunktion von dezentrierten optischen Systemen(1976) Beyeler, Bernhard H.; Tiziani, Hans J.Der Einfluß von Fabrikationsfehlern, unter spezieller Berücksichtigung von Zentrierfehlern, auf die optische Übertragungsfunktion, wird diskutiert. Dabei wird mit Hilfe der Störungsrechnung für kleine Dezentrierungen die Änderung der Wellenfront und damit die entsprechende Abweichung der OTF bestimmt. Daraus folgt eine relativ einfache Abschätzung der zulässigen Toleranzen. Die vorgestellten experimentellen Ergebnisse bestätigen die theoretischen Studien.Item Open Access Resonance and relaxation attenuation by neutral acceptors in a magnetic field(1977) Schad, Hanspeter; Lassmann, Kurt; Zeile, HeinrichFine 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.Item Open Access Beurteilung der Bildqualität von Luftbildkammern(1977) Tiziani, Hans J.La fonction de transfert optique (OTF) se révèle un moyen très précieux pour comparer et se rendre compte de la qualité des systèmes optiques. 0n peut meme tenir compte des facteurs de l'environnement, tels que le mouvement des avions et de l'influence de l'atmosphère sur la qualité d'image. Les valeurs mesurées péuvent etre comparées aux valeurs calculées á partir des caractéristiques des lentilles. A l'aide d'un modèle basé sur des experiences, il fut possible d'établir une courbe de la valeur des seuils. Elle permet une comparaison entre les resultats basés sur la fonction de transfer de modulation et les resultats obtenus par des tests habitueIs de mesure du puvoir séparateur. Actuellement nous cherchons à réduire le volume des données provenant de calculs et de mesures, pour établire des indices de qualité et de focalisation utilisables en pratique.Item Open Access Transanular interaction in [2.2]phanes: [2.2](2,7)pyrenophane(1976) Schweitzer, Dieter; Hausser, Karl H.; Kirrstetter, Reiner G. H.; Staab, Heinz A.The emission spectra of [2.2](2,7)pyrenophane and the zero field splitting parameters D and E of its excited triplet state were measured in glasses and in small single crystals at 1.3 K. The results are being compared with monomer pyrene and 2,7 dimethylpyrene in liquid and solid solutions as well as in single crystals.Item Open Access Effect of a sharp bend on the transmission of neutron guide tubes of circular cross section(1976) Maysenhölder, WaldemarA Monte Carlo calculation has been performed to investigate the effect of a sharp bend on the transmission of a neutron guide tube for neutrons in the velocity range of cold to ultra-cold. The results are compared with the predictions of the analytical solution to a simple related case in two dimensions.Item Open Access Electronic properties of two isomeric charge transfer [2.2]paracyclophanes(1976) Schweitzer, Dieter; Hausser, Karl H.; Taglieber, Volker; Staab, Heinz A.The emission spectra and the zero field splitting parameters of the two diastereomeric 4,7-dicyano-12,15-dimethoxy-[2.2] paracyclophanes 3 and 4 in comparison to the corresponding monomers 1 and 2 were investigated in order to study the orientation dependence of charge transfer (CT) interactions. The general results in glasses (PMMA) are: broad structureless emission bands with large spectral overlap between fluorescence and phosphorescence; strong reduction of the zero field splitting parameters D and D* by a factor of two for the pseudo-ortho isomer 3 and by a factor of four for the pseudo-geminal isomer 4 showing the strong effect of the geometrical orientation. In single crystals of the same phanes the zero field parameters were found to be further reduced to about one fifth of the value of the monomers which indicates, in accordance with the emission spectra, an additional intermolecular interaction between adjacent phanes.Item Open Access Transannular interactions in [2.2] phanes as studied by luminescence and optical detection of magnetic resonance(1976) Schweitzer, Dieter; Colpa, Johannes Pieter; Hausser, Karl H.; Haenel, Matthias; Staab, Heinz A.Emission spectra of different types of [2.2] naphthalenophanes were measured at 1.25 K in glasses as well as in small single crystals. In addition, the D and E values of the excited triplet states were studied by optical detection of magnetic resonance in zero field and the results compared with the corresponding monomeres.Item Open Access Phonon scattering due to deep acceptors in semiconductors(1976) Combarieu, Andre de; Lassmann, KurtWe 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).Item Open Access 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).