Physical properties of Ag2S-As2S3 glassy alloys have been studied as a function of the Ag atomic concentration x. With an increase in x, the optical-absorption edge exhibits a red shift, while the steepness of the Urbach tail changes little. In the glasses with x≥15, the electrical conductivity is governed by Ag+ ionic conduction. The ionic conductivity exponentially increases with x, and in contrast the hole conductivity hardly changes with x; however, the activation energies for the ionic and the hole conductivity are nearly the same at about 0.4 eV for compositions with 15 ≤x≤35. These observations are discussed on the basis of atomic and electronic structures in Ag2S-As2S3 glasses.

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Photoconductive and photovoltaic responses in glassy Ag–As–S ion-conducting semiconductors have been studied. The ac conductivity of the glass increases with illumination, while the increase is ascribed to enhanced ionic conduction caused by temperature rise and to interfacial photoeffects. Bulk photocurrent is not detected. By contrast, photovoltages appear in Ag–As–S samples having sandwich and floating electrodes. The photovoltaic characteristics are discussed in terms of classical electrodynamics assuming interaction between electronic carriers and Ag+ ions.

Electronic structures of Ag–As–Se glasses, which possess ion-hole mixed conduction, have been studied using a scanning tunneling microscope operating in tunneling-spectroscopy modes. The tunneling spectra show marked dependence on the scan speed of tip voltage. This scan-speed dependence appears to be caused by Ag+-ion migration which is induced by electric fields generated by tips.

The first example of a one-step introduction of a carbonyl group to C(15) of the 5a-androstane skeleton, based on a long-range intramolecular hydrogen abstraction by alkoxyl radicals, generated by irradiation of 5a-androstane esters carrying a benzhydryl group in carbon tetrachloride containing mercury(i1) oxide and iodine, is described.In an earlier paper,2 we reported a two-step long-range intramolecular hydroxylation of C(25) of the cholestane side-chain, based on a long-range intramolecular hydrogen abstraction by alkoxyl radicals generated by the irradiation of hypoiodites of esters carrying a benzhydryl group. In this communication we report the one-step introduction of a i ii, iii D (2) * R and S + (4) (3) * R and S Scheme 1. Reagents and conditions: i, NaBH4-MeOH, 25 "C; ii, HgO-12-CC14; iii, hv.