@ JUL 2 9 1963

THE UNIVERSITY OF WISCONSIN

MADISON 6

DEPARTMENT OF PHYSICS

STERLING HALL

July 25, 1963

Professor Joshua Lederberg
Department of Genetics

Stanford University School of Medicine
300 Pasteur Drive

Palo Alto, California

Dear Joshua:

I have talked with a few of our people here in
regard to the problems you bring up and have no clear
answers. We have studied high energy (1 MeV) molecular
ions as they move through a metal target. In this case the
electron appears to be lost very close to the surface,
probably in the first few atomic layers and the two protons
then move apart. I should expect this behavior for 10 keV
molecular ions but at this energy more would be back scattered.
I should expect practically all back scattered particles to
be atomic and you would have a mixture of Hy. HY, and Hj. A
number of people working with Jim Tuck at Los Alamos
investigated charge states of protons that traveled through
thin foils and emerged at low energy. I believe I heard
J.A. Phillips of Los Alamos give a talk-on this subject. I
haven't found a reference for this work but believe it was in
about 1955.

Even at energies of 100 eV I would expect back
scattered particles to be atomic and to be a mixture of Hy, HY. and
H..
1
Particles that pass into the metal are expected to be
fairly mobile in many metals and to exist as separate protons.

If the ions have energies of only a few electron volts
the situation may be much different. Atomic hydrogen impinging
on a cold metal re-emerges as molecular hydrogen. I should
expect low energy (say 10 eV or less) molecular ions to behave

om

u

Ad Hf
ty

Professor J. Lederberg -2- July 25, 1963

similarly. However there might be interchange so that
the pair of protons coming off might not be the pair that
hit. If the metal is hot (say 2000° C) 10 eV molecules or
HS hitting will be dissociated and will come off as neutral
atoms.

We have been looking at chemical reactions
involving hydrogen on metal surfaces. These may be
important if the ions have very low energies.

Sincerely,

Uf,

R. G.
Professor of Physics

RGH: jp