The phonon-assisted luminescence in AgBr: I is discussed in the framework of a conventional configuration coordinate model in which both optical and acoustic phonons are coupled to the excited electronic states. We derive the expression for the luminescence intensityusing the coherentphonon description for the displacedoscillator (excited impurity) in a consequent way. As compared to the conventional derivation we gain in simplicity and transparency of the calculation. With the formulae derived, the experimental results concerning the spectral features of the luminescence as well as their dependence on temperature are well reproduced. In particular the importance of the acoustical phonon contribution in determining the correct intensity and its temperature dependence is stressed. Furthermore the question of the interpretation of the experiments in terms of the introduced coherent phonon states is discussed.

We have studied the dependence of the lattice parameter of silicon on isotopic mass, using high-resolution photoluminescence spectroscopy to detect splittings of the shallow donor bound exciton transitions in epitaxial layers of either isotopically enriched 28 Si or 30 Si grown on silicon substrates of natural isotopic composition. The slight lattice parameter mismatch between the isotopically enriched epitaxial layer and the natural silicon substrate induces a biaxial strain in the epitaxial layer, which results in a splitting of the hole states in the bound exciton. This can be detected with remarkable precision, especially in the highly enriched 28 Si epilayers, where the bound exciton lines are extremely sharp.

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cis-Hydroxyamination of endo-2-acetoxymethyl-7-oxabicy-cleophilic substitution with an acetate ion, the known 2-acetclo[2.2.l]hept-5-ene (1) under Sharpless conditions affords two amido-5a-carba-2-deoxy-a-~~-allo (25) and -gulopyranose tepositional isomers 3 and 7 of 5-endo-acetoxymethyl-2(3)-exo-traacetates (26), and new 3-acetamido-5a-carba-3-deoxy-a-~~-hydroxy-3(2)-exo-p-toluenesulfonamido-7-oxabicyclo-allopyranose tetraacetate (30) have been obtained. Likewise, [2.2.l]heptanes. Cleavage of the 1,4-anhydro ring of the cor-the new 3-acetamido-5a-carba-3-deoxy-~-~~-talopyranose teresponding acetyl derivatives 4 and 8 with 18% hydrogen bro-traacetate (39) has been prepared by starting from the exomide in acetic acid at 80°C produces several bromodeoxy isomer 2. aminocyclitol derivatives, from which, on hydrolysis or nu-

The 7‐oxabicycloheptenecarboxylic acid ester (I) is converted to the diacetate (III) which is reduced and acetylated, yielding the triacetate (IV).

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