An experimental technique in which radioactive ${\mathrm{Li}}^8$ atoms are introduced into the gas of a cloud chamber has been used to determine the energy distribution of the alpha-particles from the ${\mathrm{Li}}^8$ breakup. The maximum of the distribution occurs at 3.3 Mev and the width of half-intensity is 1.2±0.2 Mev. The theoretical distribution $N_{\alpha }d{E}_{\alpha }=[P_{\alpha J}\frac{{(Q-2\mathrm{}{E}_{\alpha })}^5}{{(E_0-2\mathrm{}{E}_{\alpha })}^2}+\frac{1}{4}{\Gamma }^2]d{E}_{\alpha }$

with $E_0=3.1\mathrm{}$ Mev, $\Gamma =0.8\mathrm{}$ Mev, and $J=4\mathrm{}$, gives good agreement with experimental data. $N_{\alpha }$ is the relative number of alpha-particle pairs, $E_{\alpha }$ is the energy of one alpha-particle, $P_{\alpha J}$ is the penetrability of one alpha-particle from a ${\mathrm{Be}}^8$ nucleus having $J$ units of total angular momentum, and $E_0$ and $\Gamma$ are, respectively, the mean energy and width at half-intensity of the excited level in ${\mathrm{Be}}^8$. No evidence was found for a short-range group of alpha-particles which would correspond to the disintegration energy of the ground state of ${\mathrm{Be}}^8$.

• Received 2 January 1948

DOI:https://doi.org/10.1103/PhysRev.73.885