Ranges and Range Straggling ofTb149, At, and Po

We report on ranges and range straggling of recoils from nuclear reactions induced by the ions ${\mathrm{C}}^{12}$, ${\mathrm{N}}^{14}$, ${\mathrm{O}}^{16}$, ${\mathrm{O}}^{18}$, and ${\mathrm{Ne}}^{22}$ with kinetic energies of 10 Mev per nucleon and less. Range-energy curves were obtained for ${\mathrm{Tb}}^{149}$ (recoil energies of 4 to 29 Mev) in Al, for At and Po (4 to 15 Mev) in Al, and for At and Po (4 to 9 Mev) in Au. Ranges of ${\mathrm{Tb}}^{149}$ at the threshold of each reaction were obtained by extrapolation. The agreement of these and the directly measured values supports the assumption of compound-nucleus formation used in calculating the recoil energies. The smaller recoil velocities in this study are of the same order as the Bohr velocity (2.2×${10}^8$ cm/sec). The values of the average range and the straggling parameter are compared with stopping theory. The contribution to the measured range straggling from the nuclear reaction is discussed. Our results and the work of others are used to obtain values of the range for ${\mathrm{Xe}}^{139}$ in Al from 0.1 to 70 Mev and for ${\mathrm{At}}^{203}$ in Au from 0.01 to 10 Mev.