${}^{7}{Li}$ and ${}^{7}{Be}$ production in the $α + α$ reaction

Differential cross sections for the

{}^{4}{He} (α, p)

reaction leading to the ground and 478-keV states of

{}^{7}{Li}

have been measured at 11 energies between 39.0 and 49.5 MeV and used to determine integral cross sections for

{}^{7}{Li}

production in

{}^{4}{He} (α, p)

. Comparison of the ground state cross sections with

{}^{7}{Li} (p, α)

data using the principle of detailed balance indicates good agreement with the most recent

{}^{7}{Li} (p, α)

measurements but not with some older results. Cross sections for

{}^{4}{He} (α, d) {}^{6}{Li}

(ground state), extracted at three energies, are consistent with the most recent

{}^{6}{Li} (d, α)

measurements. Cross sections for

{}^{7}{Be}

production via

{}^{4}{He} (α, n) {}^{7}{Be}

were determined at nine energies between 39.4 and 47.4 MeV by direct collection of the

{}^{7}{Be}

and detection of the

γ

rays following its decay. These cross sections are essentially identical to the

{}^{7}{Li}

production cross sections above 43 MeV but are smaller below this energy because of threshold effects. The

{}^{4}{He} (α, p)

and

{}^{4}{He} (α, n)

reactions are involved in several mechanisms which have been proposed to explain the universal abundance of

{}^{7}{Li}

, and calculations of these processes have assumed cross sections larger than our data. We therefore confirm earlier conclusions that

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Li7andBe7production in theα+αreaction