Secondary Electrons of High Velocity From Metals Bombarded with Cathode Rays

The magnetic spectra of high-speed secondary electrons emitted by Au, Ag, and Al, when bombarded with cathode rays of from 16 to 40 kv., have been photographed and densitometered. Beginning at the high-velocity end, the density is zero down to energy $e{V}_0$ equal to that of a primary ray, then rises rapidly to a maximum at about $0.94e{V}_0$ for Au or Ag, or $0.85e{V}_0$ for Al, and then declines. The density is everywhere continuous. Its first derivative may be discontinuous at $e{V}_0$ but nowhere else.

Thin targets show spectra sufficiently like those of thick targets to indicate that most of the secondary electrons come from very near the surface: for Au, within 0.2 micron even up to 40 kv; for Ag, over 0.2 micron only above 20 kv; for Al, over 0.5 micron only above 20 kv.

Obituary Notice

It is with great regret that we must record the death of the brilliant and promising young scientist whose work is described here. With his great enthusiasm for research, his conscientious thoroughness both instictive and cultivated by his early education in Germany, and his unusually likable personality, he had every prospect of success and enjoyment in scientific research, and his death was a great loss, both to science and to his friends.

This paper is taken from his thesis for the degree of Master of Arts. As his death occurred in the sinking of the San Juan, on his way home to Los Angeles, just after handing in the thesis, he never had an opportunity to condense it for publication. This duty was therefore performed by the instructor, D. L. Webster, with whom he had done the research, but from whom only very little help was ever needed by such an original and able man as Paul Wagner.