Alvin J. Cohen

Ultraviolet and infrared absorption of fused Germania

Abstract Fused germania (GeO2) contains an intense absorption band centered at 2445 A and caused by a reduced germanium species, probably Ge(II). This band has a half-width comparable to that of a band centered at 2429 A in certain fused silicas and produced by the same reduced germanium species contained as an impurity. The band in germania is bleached by ultraviolet light and X-rays accompanied by an increase in absorbency below 2200 A. The energy gap for fused germania is slightly higher than a value published for hexagonal germanium dioxide, which indicates the latter is probably in error. The infrared spectrum of fused germania is also presented.

VARIABLE TRANSMISSION SILICATE GLASSES SENSITIVE TO SUNLIGHT

The process of variable transmission in silicate glasses has been accomplished by optically pumping color centers by electron transfer from europium (II) or cerium (III) which absorb sunlight at higher energies than the color center. Absorbed energy quickly pumps the visible color center band to a maximum. Upon removal of activating light, the visible color spontaneously decays.

Anisotropic Color Centers in α Quartz. Part I. Smoky Quartz

The color center at 460 mμ produced by x‐irradiation of naturally colorless or bleached smoky quartz is anisotropic. The absorption maximum of this color center for the extraordinary ray is 460 mμ and for the ordinary ray is 485 mμ. A second anisotropic peak with maximum in the vicinity of 625 mμ for the extraordinary ray is also present. The relative anisotropy of these color centers in a natural, a Bell synthetic and a Brush synthetic quartz are compared and found to be nearly identical in the case of the synthetic quartzes studied. The absorption coefficients of these color centers x‐rayed to saturation are compared with total aluminum content for five specimens.

Coesite Discoveries Establish Cryptovolcanics as Fossil Meterorite Craters

Discovery of coesite in St. Peter sandstone from the central uplift of the Kentland structure, Newton County, Indiana, and in shatter cones of Lilley dolomite of Middle Silurian age from the central uplift of the Serpent Mound structure near Sinking Springs, Ohio, proves that shatter cones are evidence of meteorite impact.

Anisotropic Color Centers in α‐Quartz. II. Germanium‐Doped Synthetic Quartz

The color center at 275 mμ produced by x‐irradiation in three specimens, two of Bell and one of Clevite synthetic quartz, depends on the presence of germanium impurity. It is absent in specimens free of germanium. The center is anisotropic with maximum absorption in the σ direction (electric vector perpendicular to the c axis). In the π direction (electric vector parallel to the c axis) the absorption is poorly resolved into two bands. The color center absorption is caused by an electric dipole transition. This center bleaches more rapidly than other color centers present in the specimens. This color center system is accompanied by the aluminum system which is in the 460 mμ region and by two other bands at 1900 and 2050 A. No relationships have been observed among these bands other than that they are found together in the three instances studied and the intensity increases with the energy of the given band. A question of a model for this center is discussed.