Non statistical reaction contributions in (α, n) excitation functions

The excitation function²⁴Mg(α, n)²⁷Si has been measured from threshold to 27 MeV excitation energy. A survey is given of the experimental excitation functions¹²C(α, n)¹⁵O,¹⁶O(α, n)¹⁹Ne,²⁰Ne(α, n)²³Mg and²⁴Mg(α, n)²⁷Si and HF calculations have been made for them. The agreement is good within a factor of 2. The deviations of the experimental data from the pure statistical cross sections show common structures which can be interpreted as direct contributions.