The Radioactive Isotopes of Scandium and Their Properties

Abstract

The results of further studies of the radioactive isotopes of scandium can be summarized as follows. (a) The activity of half-life 53\ifmmode\pm\else\textpm\fi{}3 min., now measured more accurately as 57\ifmmode\pm\else\textpm\fi{}2 min., produced by bombarding calcium with deuterons, which emits $\ensuremath{\beta}\ensuremath{-}\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{s}$ of energy 1.8\ifmmode\pm\else\textpm\fi{}0.1 Mev previously assigned to ${\mathrm{Sc}}^{41}$ is shown to be probably due to ${\mathrm{Sc}}^{49}$. ${\mathrm{Sc}}^{49}$ can be produced by the decay of ${\mathrm{Ca}}^{49}$ and from titanium by bombardment with fast neutrons. It emits no $\ensuremath{\gamma}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}$. (b) ${\mathrm{Sc}}^{42}$, half-life 13.4\ifmmode\pm\else\textpm\fi{}0.3 days, emits positrons of maximum energy 1.4\ifmmode\pm\else\textpm\fi{}0.1 Mev. (c) The continuous spectrum of ${\mathrm{Sc}}^{43}$ is complex, there being two groups of positrons and $\ensuremath{\gamma}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}$ of energy 1.0\ifmmode\pm\else\textpm\fi{}0.1 Mev. (d) The 52-hour isomer of ${\mathrm{Sc}}^{44}$ is the metastable form decaying by emitting highly internally converted $\ensuremath{\gamma}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}$ of energy 250 kev. (e) There is only one form of ${\mathrm{Sc}}^{46}$ of half-life 85\ifmmode\pm\else\textpm\fi{}1 days, emitting $\ensuremath{\beta}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{y}\mathrm{s}$ of energy 0.26\ifmmode\pm\else\textpm\fi{}0.01 Mev (>95 percent) and 1.5\ifmmode\pm\else\textpm\fi{}0.1 Mev (5 percent) and $\ensuremath{\gamma}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}$ of energy 1.25\ifmmode\pm\else\textpm\fi{}0.1 Mev. (f) ${\mathrm{Sc}}^{47}$, half-life 63\ifmmode\pm\else\textpm\fi{}2 hours, emits $\ensuremath{\beta}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{y}\mathrm{s}$ of energy 1.1\ifmmode\pm\else\textpm\fi{}0.1 Mev. (g) ${\mathrm{Sc}}^{48}$, half-life 44\ifmmode\pm\else\textpm\fi{}1 hours, emits $\ensuremath{\beta}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{y}\mathrm{s}$ of energy 0.5\ifmmode\pm\else\textpm\fi{}0.1 Mev (\ensuremath{\sim}90 percent) and 1.4\ifmmode\pm\else\textpm\fi{}0.1 Mev (\ensuremath{\sim}10 percent) and $\ensuremath{\gamma}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}$ of energy 0.9\ifmmode\pm\else\textpm\fi{}0.1 Mev. The following previously unreported reactions have been established: