  Nuclear reactions involving alpha particles play an important role in various
astrophysical processes such as the gamma-process of heavy element
nucleosynthesis. The poorly known low-energy alpha-nucleus optical (AOMP)
potential is a key parameter to estimate the rates of these reactions. The AOMP
can be tested by measuring the cross section of alpha-scattering as well as
alpha-induced reactions. Low energy elastic alpha-scattering on 144Sm has
recently been measured with high precision. The aim of the present work was to
complement that work by measuring the (a,n) cross sections on 144Sm at low
energies. The experimental data shall be used to constrain the AOMP. From this
potential the 144Sm(a,g)148Gd reaction rate can be derived with reduced
uncertainties. The 144Sm(a,n)147Gd reaction was studied by bombarding Sm
targets with alpha-beams provided by the cyclotron accelerator of Atomki. The
cross section was determined using the activation method. The gamma-radiation
following the decay of the 147Gd reaction product was measured with a HPGe
detector. The experimental data are analyzed within the statistical model. The
cross section was measured in the alpha-energy range between 13 and 20 MeV in 1
MeV steps, i.e., from close above the (a,n) threshold. The results were
compared with statistical model calculations using various approaches and
parametrizations for the AOMP, and excellent agreement was obtained for two
recent potentials. However, these potentials cannot reproduce literature data
for the 144Sm(a,g)148Gd reaction with the same accuracy. Constraints for the
AOMP were derived from an analysis of the new 144Sm(a,n)147Gd data and
literature data for 144Sm(a,g)148Gd. These constraints enable a determination
of the reaction rate of the 144Sm(a,g)148Gd reaction with significantly reduced
uncertainties of less than a factor of two.
