August 29, 1962

MEMORANDUM
TO: Professor Lederberg
FROM: E.C. Levinthal

Professor R.Castaing of the University of Paris, at the recent
International Symposium on X-ray Optics and X-ray Microanalysis described
briefly an instrument which, | believe, demonstrates the feasibility of the
application we are considering of a mass spectrometer. His instrument
has a beam of protons or argon which illuminates the sample. The surface
molecules of the sample which are ejected are imaged on a target. The
electrons ejected from this target in turn form an image on a fluorescent
screen which can be observed or photographed. The adjustment of the
mass spectrometer determines the mass number of the molecules whose
surface distribution on a sample is imaged. ! believe he said he had
achieved or expects to achieve 300 angstrom units resolution for aluminum.
The few slides he showed seemed to show about this resolution.

bi lvysry