Absolute neutron activation cross sections at 14.8 Mev have been measured for bismuth, copper, titanium, and aluminum based on comparison with the ${\mathrm{Cu}}^{63}(n, 2n){\mathrm{Cu}}^{62}$ reaction (556 millibarns) which served as a standard for monitoring the flux. The reactions studied, measured half-lives, and cross sections are: ${\mathrm{Bi}}^{209}(n, \alpha ){\mathrm{Tl}}^{206}$, 4.29±0.05 min, 1.1±0.3 mb; ${\mathrm{Bi}}^{209}(n, p){\mathrm{Pb}}^{209}$, 3.31±0.03 hours, 0.83±0.40 mb; ${\mathrm{Bi}}^{209}(n, \gamma ){\mathrm{Bi}}^{210}$, ≤1.7 mb; ${\mathrm{Cu}}^{65}(n, 2n){\mathrm{Cu}}^{64}$, 12.85±0.05 hours, 954±130 mb; ${\mathrm{Cu}}^{65}(n, p){\mathrm{Ni}}^{65}$, 2.56±0.20 hours, 27±11 mb; ${\mathrm{Ti}}^{50}(n, p){\mathrm{Sc}}^{50}$, 1.8±0.2 min, 27±6 mb; ${\mathrm{Ti}}^{50}(n, p){\mathrm{Sc}}^{50}$, 22±3 min, 48±15 mb; ${\mathrm{Ti}}^{50}(n, \gamma ){\mathrm{Ti}}^{51}$, ≤9 mb; ${\mathrm{Ti}}^{49}(n, p){\mathrm{Sc}}^{49}$, 58±2 min, 29±5 mb; ${\mathrm{Ti}}^{48}(n, p){\mathrm{Sc}}^{48}$, 44.0±0.9 hours, 58±8 mb; ${\mathrm{Ti}}^{47}(n, p){\mathrm{Sc}}^{47}$, 3.45±0.06 days, 230±40 mb; ${\mathrm{Ti}}^{46}(n, 2n){\mathrm{Ti}}^{45}$, 3.06±0.08 hours, 50.4±8.0 mb; ${\mathrm{Ti}}^{46}(n, p){\mathrm{Sc}}^{46}$, 85±2 days, ∼520 mb; ${\mathrm{Al}}^{27}(n, \alpha ){\mathrm{Na}}^{24}$, 15.00±0.06 hours, 114±7 mb; ${\mathrm{Al}}^{27}(n, p){\mathrm{Mg}}^{27}$, 9.46±0.02 min, 53±5 mb.

Comparisons of the experimental cross sections with values estimated according to the continuum theory of the compound nucleus outlined by Blatt and Weisskopf are in agreement within an order of magnitude, except in the case of the bismuth results which exhibit large discrepancies.

From irradiations of natural titanium and highly enriched ${\mathrm{Ti}}^{50}$, a new activity was observed having a half-life of 22±3 minutes. This activity is not produced from enriched ${\mathrm{Ti}}^{47}$ or ${\mathrm{Ti}}^{49}$ samples, and it is therefore assigned tentatively to an isomer of ${\mathrm{Sc}}^{50}$. Further work on this activity is in progress.

• Received 18 November 1958

DOI:https://doi.org/10.1103/PhysRev.115.989