Despite the fact that the University of Illinois campus is “centrally isolated” more than 80 physicists (including the discoverer, Rudolf Mössbauer) from 23 university, government, and industrial laboratories in eight foreign countries and the United States converged on Allerton House, the University of Illinois conference retreat, on June 5. They came to report their most recent, unpublished experiments and to present and discuss their ideas for future research in the exciting field of recoilless gamma‐ray absorption. The meeting was held as an On‐Site Advisory Meeting to the Air Force Office of Scientific Research; it was arranged in less than six weeks by Hans Frauenfelder of the University of Illinois with the support and cooperation of Max Swerdlow (Solid State Directorate, AFOSR). All discussions were informal and it was assumed that everyone at the meeting knew everything published on the Mössbauer effect. At each of three half‐day sessions several related problems were presented.

1.
A term used by Debye to describe Ithaca, N.Y., and equally applicable to Urbana, Illinois.
2.
Normally, in the process of emission or absorption a nuclear gamma ray loses an amount of energy large compared to the natural line width. This loss is due to Doppler effect and the energy goes into recoil motion of the emitting or absorbing nucleus, Mössbauer [
Z. f. Physik
151
,
124
(
1958
)] found that under favorable circumstances, namely for an atom tightly bound in a solid at low temperature, emission and absorption can occur without such an energy loss. The recoil energy is taken up by the crystal as a whole, without emission of phonons. This effect, first found in Iridium191, makes it possible to observe resonance absorption of nuclear gamma rays without high speed rotors or elevated temperatures. It opened the way to direct measurements of the widths of narrow transition lines, as well as to the observation of small energy shifts due to nuclear, atomic, and macroscopic causes.
The interested reader is referred to the following review papers:
S.
De Benedetti
, “
The Mössbauer Effect
”,
Scientific American
202
,
72
(
1960
);
W.
Kock
, “
The Mössbauer Radiation
”,
Science
131
,
1588
(
1960
);
and H. Lustig, “Mössbauer Effect”, to be published in the American Journal of Physics, Jan. 1961.
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