Emilio Segrè

Zur Theorie der Hyperfeinstruktur

ZusammenfassungDie Hyperfeinstrukturen der Elemente: Li, Na, Cu, Ga, Rb, Cd, In, Cs, Ba, Au, Hg, Tl, Pb, Bi, die experimentell gut bekannt und für die Theorie relativ leicht zugänglich sind, werden untersucht. Insbesondere wird diskutiert, wie weit die beobachteten Hyperfeinstrukturen bereits mit der Hypothese eines magnetischen Kernmoments gedeutet werden können. Es ergibt sich, daß die Hypothese einer magnetischen Kopplung in keinem Falle mit den experimentellen Resultaten in Widerspruch ist, wenn man den zahlreichen Störungen, auch zwischen verschiedenen Elektronenkonfigurationen, Rechnung trägt; sie reicht aus, um die allgemeinen Züge des gesamten Beobachtungsmaterials wiederzugeben, doch kann man die Möglichkeit nicht ausschließen, daß andere Umstände noch kleine Störungen bedingen. Schließlich wird betrachtet, welche Schlüsse man aus den Experimenten auf die magnetischen Momente der Kerne ziehen kann.

Experiments on N-P Scattering with 260-Mev Neutrons

UNIVERSITY OF CALIFORNIA TWO-WEEK LOAN COPY This is a Library Circulattng Copy which may be borrowed for two weeks. For a personal retent ion copy, call Tech. Info. Diuision, Ext. 5545 BERKELEY, CALIFORNIA

The Discovery of Nuclear Fission

Few modern discoveries have influenced mankind so rapidly and so profoundly as has nuclear fission, and few have had such an intricate history. Thus it is natural that the discovery of fission by Otto Hahn and Fritz Strassmann in December 1938 is remembered and commemorated in many places on its 50th anniversary. I participated in the early experiments in Rome, and later in the US, and I knew most of the principals well, except for Strassmann. I will try to present a brief outline of the discovery and its antecedents.

Der Zeemaneffekt von Quadrupollinien bei den Alkalien

ZusammenfassungDie vorliegende Arbeit enthält eine eingehende Untersuchung der ersten2S-2D-Kombinationen von Na und K im Magnetfeld. Die Rubinowiczsche Theorie der Quadrupolstrahlung ist daran bestätigt. Der magnetische Umwandlungseffekt bei Quadrupollinien ist untersucht worden.

Example of an Antiproton-Nucleon Annihilation

The existence of antiprotons has recently been demonstrated at the Berkeley Bevatron by a counter experiment. The antiprotons were found among the momentum-analyzed (1190 Mev/c) negative particles emitted by a copper target bombarded by 6.2-Bev protons. Concurrently with the counter experiment, stacks of nuclear emulsions were exposed in the beam adjusted to 1090 Mev/c negative particles in an experiment designed to observe the properties of antiprotons when coming to rest. This required a 132 g/cm2 copper absorber to slow down the antiprotons sufficiently to stop them in the emulsion stack. Only one antiproton was found in stacks in which seven were expected, assuming a geometric interaction cross section for antiprotons in copper. It has now been found that the cross section in copper is about twice geometric, which explains this low yield.

Experiments on Nucleon-Nucleon Scattering with 280 MEV PolarizedProtons

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Experiments on Antiprotons: Antiproton-Nucleon CrossSections

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Experiments with 315-Mev Polarized Protons Elastic Scattering by Complex Nuclei

In this paper experiments a r e reported on annihilation and sca t te r in f: of antiprotons in H 0 , D20, and 02. F r o m the data measured i t i s possible 2 to obtain an antiproton-proton and a n antiproton-deuteron c r o s s section a t 457 Mev (lab). Fur the r analysis gives the p-p and p-n c r o s s sections a s 104 m b for the H-p reaction c r o s s section and 113 m b for the p-n reaction c r o s s section. The respective annihilation c ross sections a r e 89 and 74 mb. The Glauber correct ion necessary in o r d e r to pass f r o m the p-d to the p n c r o s s section by subtraction of the p-p c r o s s section i s unfortunately la rge and somewhat uncertain. The data a r e compared with the p-p and p-n c r o s s sections and with other resu l t s on p p collisions. EXPERIMENTS ON ANTIPROTONS: ANTIPROTON-NUCLEON CROSS SECTIONS* Owen Chamberlain, Donald V. Keller, Ronald Mermod, Emilio segrk , Herbert M. Steiner, and Tom Ypsilantis Radiation Laboratory University of California Berkeley, California

The Antiproton-Nucleon Annihilation Process (AntiprotonCollaboration Experiment)

In this paper we descr ibe experiments with high-energy polarized protons, ( * 3 15 Mev), their production, and their scattering f rom complex nuclei. We give the essent ials of the theory of polarization of par t ic les of spin 1/2 in a form suitable to the interpretation of the experimental resu l t s . Included i s a detailed description of the experimental techniques, the charac ter i s t ics of the polarized beam, and a discussion of the e r r o r s of measurement . The beam was 76% polarized and the maximum beam current was approximately 10 5 protons per second. Results of the scattering experiments on beryllium, carbon, aluminum, calcium, iron, and tantalum a r e descr ibed. Some resu l t s of tr iple -scat ter ing experiments, which further determine the scattering mat r ix , a r e a l so given, The relation to the experimental resu l t s of the various, theories proposed for explaining the polarization by scat ter ing i s discussed. Only qualitative agreement with the theoretical studies made on current models is achieved. Although many of the features predicted by the usual type of potentials a r e present , no single potential can account for all the observed facts .

Antiproton Star Observed in Emulsion

In the exposure to a 7 0 0-MeV/c negative particle beam, 35 antiproton stars have been found. Of these antiprotons, 21 annihilate in flight and three give large-angle scatters ( {Theta} > 15 , T{sub P-} > 50 Mev), while 14 annihilate at rest. From the interactions in flight we obtain the total c r o s s section for antiproton interaction