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the lifetimes and intensities of positrons annihilating in polysyrene (to be reported 10 ) will be summarized in support of the above discussion. We find three components in this glass. I x (^35%) is due to free positrons not trapped or in some short-lived bound state (^ 20%) and/>-Ps (^15%). I 2 (J*27%) is due to the annihilation of free positrons in regions of order due to nodules 11 or spherically symmetric strain fields. 12 I 3 (^38%) is due to the annihilation of positrons in the amorphous regions by pickoff of o-Ps. A plot of r 3 (c*2 nsec) versus the temperature T shows a linear relationship with positive slope, changing to a steeper positive slope at the glass transition. 6 A plot of r 2 (^0.4 nsec) versus T shows a linear relation with positive slope, similar to r 3 versus T, below the glass transition where r 2 changes abruptly from about 0.42 to 0.47 nsec. Thus the glass transition seems to consist of a combination of first-order and second-order transitions. The lifetime of the r x component changes abruptly from 0.13 nsec in the glass to about 0.16 nsec in the highly viscous liquid. While results for temperatures below the glass transition were easily fitted by our model, results for temperatures above the glass transition (highly viscous liquid) were difficult to fit, although the data fit three components better than two or four. Experiments to measure the temperature dependence of positron lifetimes and intensities in polyethylene and to continue the electric field experiments for polar molecules, such as Teflon, are planned.

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The absorption structure of five light metals has been measured from the onset of Kand LII, 111-absorption up to photon energies of 140 eV (170 eV for Be). The edges a t the threshold are followed by several broad peaks which are distributed over the total energy region covered by these measurements. There is a striking similarity between the LII,III-absorption spectra of Na, Mg, and Al; a similarity can also be seen between the K-absorption spectra of Li and Be.Das optische Absorptionsverhalten yon fiinf Leichtmetallen wurde vom Einsatz der Kbzw. LII,III-Absorption bis zu Photonenenergieii von 140 eV (bei Be bis 170 eV) gemessen. Neben den Kanten beim Einsatz wurden im ganzen Spektralbereich mehrere breite Absorptionsmaxima beobachtet. Der allgemeine Verlauf der L~~,~~~-Absorptionsspektren von Na, Mg und A1 stimmt gut iiberein; Ahnlichkeiten zeigen sich auch bei den K-Absorptionsspektren von Li und Be.