Showing papers by "Tunis University published in 1988"
TL;DR: The RRS and RPL intensity is dominated by competition between radiative recombination at rate ${W}_{R}$ and the energy transfer mechanism of excitons between states of the localization tail.
Abstract: Resonant Raman scattering (RRS) and resonant photoluminescence (RPL) studies on localized exciton states due to disorder in indirect-band-gap ${\mathrm{GaAs}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{P}}_{\mathrm{x}}$ alloys show that the RRS and RPL intensity is dominated by competition between radiative recombination at rate ${W}_{R}$ and the energy transfer mechanism of excitons between states of the localization tail. The rate of change of the transfer probability d[ln(${W}_{\mathrm{tr})]/\mathrm{dE}}$ has been evaluated near the point where ${W}_{\mathrm{tr}={W}_{R}}$.
45 citations
23 citations
TL;DR: In this article, the spectrum of neutral 121Sb emitted by an electrodeless discharge lamp has been observed in the range 2 536-24 786 cm−1 and the wavelengths of 617 lines have been measured.
Abstract: The spectrum of neutral 121Sb emitted by an electrodeless discharge lamp has been observed in the range 2 536–24 786 cm−1. The wavelengths of 617 lines have been measured. The hyperfine-structure splitting factors of the levels were established for 77% of these lines. Thirty-two new energy levels were found, and several J values were revised. The Slater–Condon method was used for the interpretation of levels in both parities, and the multiconfiguration eigenfunctions were applied to the parametric study of the hyperfine-structure factors A and B. The multichannel quantum-defect theory analysis of high odd levels having J = 1/2 and J = 3/2 was also revised.
19 citations
4 citations
TL;DR: Cristallisation dans P2 1 /a avec affinement jusqu'a 0,0359 as mentioned in this paper was performed by using tunnels entrecroises which were constructed by an anion tridimensionnel Sb 3 As 2 O 14 3− possedant des canaux paralleles aux axes b and c, dans lesquels viennent se loger les cations Na +
Abstract: Cristallisation dans P2 1 /a avec affinement jusqu'a 0,0359. Structure a tunnels entrecroises dont la charpente est constituee par un anion tridimensionnel Sb 3 As 2 O 14 3− possedant des canaux paralleles aux axes b et c, dans lesquels viennent se loger les cations Na +
4 citations
01 Jan 1988
TL;DR: The coupe de la terrasse du Pleistocene moyen de l'oued Ahmadi as discussed by the authors is organized en quatre sequences sedimentaires which pourraient traduire l'existence de quatre oscillations climatiques dans un climat restant aride dans l'ensemble.
Abstract: La coupe de la terrasse du Pleistocene moyen de l'oued Ahmadi est organisee en quatre sequences sedimentaires qui pourraient traduire l'existence de quatre oscillations climatiques dans un climat restant aride dans l'ensemble. La genese d'une croute calcaire posterieurement a celle d'une croute gypseuse indique un renversement episodique de la tendance generale a l'aridification du climat pendant le Quaternaire.
3 citations
26 Sep 1988
3 citations
TL;DR: In this article, the X-ray diffraction lines of copper indium disulphide were obtained by airless spraying an aqueous solution containing cuprous and indium chlorides, ammonium and hydrazinium chloride, and thiourea.
2 citations
2 citations
Posted Content•
TL;DR: In this paper, the authors developed a theory of sharecropping which emphasizes the dual role of moral hazard in the provision of effort and financial constraints in a large variety of contracts as observed in the region of El Oulja in Tunisia.
Abstract: This paper develops a theory of sharecropping which emphasizes the dual role of moral hazard in the provision of effort and financial constraints. The model is compatible with a large variety of contracts as observed in the region of El Oulja in Tunisia. Using an original data set including financial data, various tests of the theory are undertaken. Production functions stressing the role of effort are estimated. The data support the theory which predicts lower efficiency when the tenant's share of output is lower. The role of financial constraints in explaining which type of contract is selected (as well as the implications that financial constraints have upon effort and therefore output) are supported by the data. (This abstract was borrowed from another version of this item.)
1 citations
TL;DR: In this article, high-resolution front views of reconstructed (111) gold surfaces have been obtained by electron microscopy, using several layer-diffracted beams, taking into account the interaction of the electrons with the reconstructed surface and with the bulk gold.
Abstract: High-resolution front views of reconstructed (111) gold surfaces have been obtained by electron microscopy, using several layer-diffracted beams. From two different models for the reconstructed surface, we have computed images taking into account the interaction of the electrons with the reconstructed surface and with the bulk gold. Comparison between these computed images and the experimental ones allows us to choose which of the models corresponds best to the experimental evidence.