$E 1$ and $E 2$ strength in ${}^{24}{Mg}$ and ${}^{26}{Mg}$ observed in $α$ -capture reactions

Excitation functions and angular distributions of the reactions

{}^{20, 22}{Ne} (α, γ_{0})

were used to study the distribution of

E 2

strength in the energy regions 14-22 MeV of

{}^{24, 26}{Mg}

, as well as to probe the importance of isospin in the decay of the

E 1

giant resonance in these nuclei. It was found that the

E 2

strength in the (

γ, α_{0}

) channel is rather uniformly distributed and accounts for about 10% of the energy weighted sum rule in each nucleus. Together with the

E 2

strength observed in lower resonances, about 45% of the sum rule is accounted for. No evidence for a compact

E 2

resonance is found. A comparison of the

E 1

distribution and total strength in the (

γ, α_{0}

) channel of the giant dipole resonances in

{}^{24, 26}{Mg}

indicates that isospin conservation may be important in these reactions. Information was also obtained on the reactions

{}^{20, 22}{Ne} (α, γ_{1})

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E1andE2strength inMg24andMg26observed inα-capture reactions