Abstract : The thesis is constituted of two different topics related to astrophysics. The titles of these topics are : "Alpha capture reaction in inverse kinematics ; measurement of 78Kr( $/alpha$ , $/gamma$ )82Sr reaction"and "Measurement of the radioactive decay of 19O and 19Ne implanted in niobium". The goal of the first part of the thesis was to establish an experimental technique for measurement of radiative alpha capture reaction at low energies in inverse kinematics. Measurement of these reactions is very important in astrophysics since it will help to improve a reliability of alpha particle optical model potentials which are used for prediction of cross sections of nuclear reaction used in different astrophysical models of supernovae explosions. In this part we insisted on a technical feasibility of this type of experiment. In the second part of the thesis, we examined the influence of the environment on the beta decay probability, in particular the influence of the electronic screening of Coulomb barrier of nuclei induced by Cooper pairs in superconductors. The indication of an extremely weak effect was noticed.