THE LEWIS EFFECT IN GAMMA-RAY RESONANCE YIELD CURVES FROM THICK TARGETS OF ALUMINUM AND NICKEL
Thesis/Dissertation
·
OSTI ID:4074426
Al targets evaporated under a variety of conditions all showed a Lewis peak from the thick-target gamma -ray yield curve over the Al/sup 27/(p, gamma )Si/sup 28/ resonance reaction at 992 kev. The peaks of all targets prepared at pressures below 4 x 10/sup -7/ mmHg rose above the plateau to a height of about l0% of the plateau yield. The targets that were prepared at higher pressures showed smaller peaks and were very likely contaminated by material given off by the outgassing of the evaporator unit. Ni targets were prepared using a sublimation process. Thick-target yield curves from the Ni/sup 58/(p, gamma )Cu/ sup 59/ resonance reaction at 1424 kev showed a Lewis peak. The size of the peak for Ni was considerably larger than for Al. In the case of Ni, the height of the peak above the plateau is about 23% of the plateau yield. Yield curves were calculated for both reactions using a collision spectrum, which takes into account the electron shells of the atom. These calculated curves fit the experimental data much better than previous calculations, which treated the electrons in the target material as free. Because of the very good agreement between the theory and the experimental data from 2 elements widely separated in atomic number, it is felt that the collision spectrum is very close to being correct. Results indicate that previous determinations of the resonance energy of these reactions are in error. The point corresponding to 1/2 the plateau yield, which has been taken in the past to correspond to the resonance energy, was found to lie about 120 ev below the resonance energy for Al and about 125 ev below for Ni. (Dissertation Abstr.)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-18-009432
- OSTI ID:
- 4074426
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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