The Induced Radioactivity of Titanium and Vanadium

A study has been made of the radioactivities induced in titanium and vanadium by irradiation with deuterons, slow and fast neutrons and in titanium with 11 Mev alpha-particles. Bombardment of titanium with deuterons renders it extremely radioactive, the radiations emitted being mainly positrons and hard gamma-rays. An analysis of the decay curve shows the presence of six radioactive isotopes. Of these three have been found to be chemically inseparable from vanadium. Evidence is considered which suggests that the isotopes formed are ${\mathrm{V}}^{48}$ half-life 16.0±0.2 days, ${\mathrm{V}}^{49}$ half-life 33±1 minutes and ${\mathrm{V}}^{50}$ half-life 3.7±0.2 hours. A short lived activity of half-life 2.8 minutes is probably due to ${\mathrm{Ti}}^{51}$ as the same isotope is formed when titanium is bombarded with slow neutrons. There is evidence of a weak activity with a half-life of 50 hours which is probably due to ${\mathrm{Sc}}^{44}$ formed in the reaction ${\mathrm{Ti}}^{46}+{\mathrm{H}}^2\to {\mathrm{Sc}}^{44}+{\mathrm{He}}^4$. ${\mathrm{Sc}}^{46}$ is also formed as evidenced by the presence of an isotope with a half-period of 85±5 days and by the energy distribution of the soft negative electrons which accompany the positrons. The energy distribution of the positrons emitted by ${\mathrm{V}}^{48}$ has been studied using a large hydrogen-filled cloud chamber. The upper limit of the spectrum is at 1.0 (5) Mev, in reasonably good agreement with the value 1.1 (5) Mev deduced from absorption measurements in aluminum. The maximum energy of the positrons from ${\mathrm{V}}^{49}$ as determined by absorption measurements in aluminum is approximately 1.9 Mev. ${\mathrm{V}}^{49}$ and ${\mathrm{V}}^{50}$ have also been formed by bombarding titanium with 11 Mev alpha-particles. In addition two new periods of 68±4 hours and longer than 180 days have been detected. The isotopes responsible for these activities have not been identified. When bombarded with fast neutrons it seems likely that ${\mathrm{Ca}}^{45}$, ${\mathrm{Sc}}^{48}$ and ${\mathrm{Sc}}^{46}$ are formed from titanium. ${\mathrm{Sc}}^{48}$ is also produced by the transmutation ${\mathrm{V}}^{51}+n^1\to {\mathrm{Sc}}^{48}+{\mathrm{He}}^4$, its half-life being 41±3 hours. In addition, evidence has been obtained for the reaction ${\mathrm{V}}^{51}+n^1\to {\mathrm{V}}^{50}+2\mathrm{}{n}^1$. This reaction can be induced by the fast neutrons from the ${\mathrm{Be}}^9$+${\mathrm{H}}^2$ reaction, though it is more probable when Li+${\mathrm{H}}^2$ neutrons are used ${\mathrm{V}}^{52}$ has been produced in several reactions; its half-life is 3.9±0.1 minutes.