ACTIVATION CROSS SECTIONS FOR 14.8-Mev NEUTRONS AND SOME NEW RADIOACTIVE NUCLIDES IN THE RARE EARTH REGION

Journal Article · Fri Apr 01 00:00:00 EST 1960 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.118.242· OSTI ID:4167367

Wille, R G; Fink, R W

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

Related Subjects

PHYSICS
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