Artificial Radioactivity ofTi45

A radioactive isotope possessing a half-life of 3.08±0.06 hours has been produced by four different types of bombardment. Evidence is presented which indicates that the activity should be assigned to ${\mathrm{Ti}}^{45}$. The four nuclear reactions are: $\{{\mathrm{Ca}}^{42}+{\mathrm{He}}^4,\to {\mathrm{Ti}}^{45}+n^1 {\mathrm{Sc}}^{45}+{\mathrm{H}}^2\to {\mathrm{Ti}}^{45}+2\mathrm{}{n}^1\}\{{\mathrm{Sc}}^{45}+{\mathrm{H}}^1,\to {\mathrm{Ti}}^{45}+n^1 {\mathrm{Ti}}^{46}+n^1\to {\mathrm{Ti}}^{45}+2\mathrm{}{n}^1.\}$ Nuclear spin considerations indicate that a fifth reaction, ${\mathrm{Ti}}^{46}(\gamma ,n){\mathrm{Ti}}^{45}$, is improbable, as was verified experimentally. Analysis of cloud-chamber pictures reveals the maximum positron energy to be 1.2 Mev. On a Sargent diagram, the reaction ${\mathrm{Ti}}^{45}\to {\mathrm{Sc}}^{45}+e^{+}$, is a permitted one. The half-life of 3.08±.06 hours for ${\mathrm{Ti}}^{45}$ is the weighted average of 3.17, 3.10, and 3.02 hours from $\mathrm{Sc}\mathrm{}(p,n)\mathrm{}$; 3.04 hours from $\mathrm{Sc}\mathrm{}(d,2n)\mathrm{}$; 3.17 hours from $\mathrm{Ca}(\alpha ,n)$; 3.0 hours from $\mathrm{Ti}\mathrm{}(n,2n)\mathrm{}$.