Positive rays produced by ultra-violet light

Experimental test for positive photo-electric emission from Au, Cu and Al. — Following the announcement by Dember in 1909 that positive emission had been observed, an attempt was made to verify its existence under improved conditions. His experiment was repeated using light from a quartz mercury arc and curves similar to his obtained. It was found, however, that when proper precautions against scattered light effects were taken, no true positive current could be detected from Au, Cu, or Al surfaces, and it is shown that the Dember effect may be accounted for on the basis of spurious currents due to scattered light. Outgassing of the surface failed to cause the appearance of any positive current.