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Vol. 65
NOTES
nately, however, size limitations in using the special target required the use of a more intense y-source, so that there still remained the possibility that source intensity is the major factor. Accordingly, spherical one-liter Pyrex reactors with thin bubble windows w r e constructed for use in Van de Graaff irradiations. While the radiation flux is still not homogeneoils in these reactors, this condition is much more closely approached than with the cylindrical reactors. With the same incident current of 10 microamperes used in the earlier hexane experiments, the cluster of points designated E was obtained for n-pentane radiolysis. These experiments indicate that a significant factor in radiolysis experiments is what may be termed target geometry or flux geometry in the radiation vessel. The observations are consistent with the interpretation that in the earlier Van de Graaff experiments using cylindrical reactors unsaturzkt,ed products which are formed in the reaction zone diffuse into the low radiation flux region of the reactor where they are not exposed to reactive intermediates formed in radiolysis. Thus the steady-state concentration of unsaturated products is much higher than under homogeneous irradiation; and
