ACTIVATION CROSS SECTIONS FOR 14.8-Mev NEUTRONS AND SOME NEW RADIOACTIVE NUCLIDES IN THE RARE EARTH REGION
Activation cross sections on 27 stable nuclides of elements Ba, Im, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, and Lu were measured for 14.8 plus or minus 0.8- Mev neutrons. Highly enriched isotopes were used as targets in most cases, and in a few instances radiochemical separations were performed whenever it was necessary and possible in view of the product half-lives. The measured cross sections for (n,2n) reactions were found to agree within an order of magnitude with predictions from statistical evaporation theory. However, experimental values of (n,p) and (n, alpha ) cross sections generally appear to be larger than calculated from continuum theory of the compound nucleus. The cross sections show no significant effects due to the 82-neutron closed shell and, furthermore, the Devkovskii effect, which is quite striking in the low Z region, appears to be negligible for (n,p) and (n, alpha ) reactions in the rare earth region. The (n,2n) cross sections show little variation with mass number at constant Z, and they exhibit a decrease with increasing mass number at N = 82. Several previously unreported activities were observed: their half-lives, assignment, and gamma radiations are as follows: 12 plus or minus 3 min Pr/sup 148/ from the Nd/ sup 148/(n,p) reaction: 0.5 plus or minus 0.1 min Sm/sup 157/ from the Gd/sup 160/ (n, alpha ) reaction, 0.57 plus or minus 0.01 Mev gamma: 7 plus or minus 1 min Tb/sup 163/ from the Dy/sup 163/(n,p) reaction, 0.18 plus or minus 0.05- Mev gamma; 3.3 plus or minus 0.5 min Ho/sup 168/ from the Er/sup 168/ (n,p) reaction, 0.85 plus or minus , 0.05-Mev gamma; 40 plus or minus 10 sec Ho/sup 170/ from the Er/sup 170/(n,p) reaction; 4.4 plus or minus 0.4 min Dy/sup 167/ from the Er/sup 170/(n, alpha ) reaction; 2.0 plus or minus 0.5 min activity with gammas at 0.18 plus or minus 0.01, 0.25 plus or minus 0.01, and 0.36 plus or minus 0.01 Mev which may be Tm/sup 176/, Er/sup 173/, or possibly isomeric Yb/sup 177m/ from enriched Yb/sup 176/, bombardments. Tentative assignment of a 5.5 plus or minus 0.5-min activity to Tm/sup 174/ is suggested from bombardment of enriched Yb/sup 174/. (auth)
- Research Organization:
- Univ. of Arkansas, Fayetteville
- NSA Number:
- NSA-14-015305
- OSTI ID:
- 4167367
- Journal Information:
- Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Vol. Vol: 118; Other Information: Orig. Receipt Date: 31-DEC-60
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
ACTIVATION- ACTIVATION ANALYSIS- ALPHA PARTICLES- COMPOUND NUCLEI- CROSS SECTIONS- DYSPROSIUM 167- ENERGY RANGE- ENRICHMENT- ERBIUM 170- EXCITATION- FAST NEUTRONS- GAMMA RADIATION- HALF-LIFE- ISOTOPES- MEASURED VALUES- MEV RANGE- NEUTRON BEAMS- NUCLEAR EVAPORATION- NUCLEAR MODELS- NUCLEAR REACTIONS- NUCLEI- - NUCLEONS- RADIOCHEMISTRY- SEPARATION PROCESSES- TARGETS
ACTIVATION- ACTIVATION ANALYSIS- ALPHA PARTICLES- COMPOUND NUCLEI- CROSS SECTIONS- ENERGY RANGE- ENRICHMENT- EXCITATION- FAST NEUTRONS- GADOLINIUM 160- GAMMA RADIATION- HALF-LIFE- ISOTOPES- MEASURED VALUES- MEV RANGE- NEUTRON BEAMS- NUCLEAR EV