In an evacuated tube in which the slightest traces of organic vapors may occur, even with liquid air cooling, insulating layers are formed on surfaces subject to electron or canal-ray bombardment. These layers may be attributed to carbon compounds, and their formation is related to the polymerization of organic vapors by electrical discharges, $\alpha$-particles, and ultraviolet light. The simple ion-deposition theory is inadequate as the layers are formed only at the point of impact of the rays on the surface. Electrical resistances and break-down potentials were observed for several films. The importance of these deposits in general experimental practice, such as the photometry of mass-spectra, is pointed out, and, amongst others, cases are cited of their influence producing contact potentials, pseudo high vacua, erroneous photographic recording and differential condensation of vapors upon previously bombarded surfaces.

• Received 18 December 1933

DOI:https://doi.org/10.1103/PhysRev.45.488