Cross sections of α -induced reactions slightly below doubly magic 40Ca from the statistical model

New experimental data for the ³⁸Ar(α ,n )⁴¹Ca and ³⁸Ar(α ,p )⁴¹K reactions were used to find a best-fit set of parameters for statistical model calculations. The very good agreement between the experimental data and the best-fit calculation confirms the applicability of the statistical model for nuclei in the vicinity of the doubly magic ⁴⁰Ca despite their relatively low level densities. The present study investigates the sensitivities and finds that the α -nucleus and the nucleon-nucleus potentials are the most important ingredients for the calculation of (α ,n ) and (α ,p ) reactions in the statistical model. Furthermore, the width fluctuation correction plays an essential role in the peculiar case of ³⁸Ar. The best-fit parameters from ³⁸Ar are applied to the mirror nucleus ³⁸Ca and the neighboring ³⁶Ar and ⁴⁰Ar nuclei. For ³⁸Ca this results in an astrophysical reaction rate of the ³⁸Ca(α ,p )⁴¹Sc reaction, which has a flatter temperature dependence compared to all previous calculations. For ⁴⁰Ar a better reproduction of ⁴⁰Ar(α ,p )⁴³K data from literature is obtained. The disagreement between calculation and an early experimental data point for the ³⁶Ar(α ,p )³⁹K reaction persists.