  Proton captures on Mg isotopes play an important role in the Mg-Al cycle
active in stellar H shell burning. In particular, the strengths of low-energy
resonances with E < 200 keV in 25Mg(p,gamma)26Al determine the production of
26Al and a precise knowledge of these nuclear data is highly desirable.
Absolute measurements at such low-energies are often very difficult and
hampered by gamma-ray background as well as changing target stoichiometry
during the measurements. The latter problem can be partly avoided using higher
energy resonances of the same reaction as a normalization reference. Hence the
parameters of suitable resonances have to be studied with adequate precision.
In the present work we report on new measurements of the resonance strengths
omega_gamma of the E = 214, 304, and 326 keV resonances in the reactions
24Mg(p,gamma)25Al, 25Mg(p,gamma)26Al, and 26Mg(p,gamma)27Al, respectively.
These studies were performed at the LUNA facility in the Gran Sasso underground
laboratory using multiple experimental techniques and provided results with a
higher accuracy than previously achieved.
