Investigation of the influence of nuclear charge and β-endpoint energy on the internal Bremsstrahlung of 89Sr and 147Pm

Past experimental studies on the inner Bremsstrahlung (IB) emission from the forbidden β-transitions have shown marked deviations from the theoretical calculations. In this paper, the IB spectra of the first forbidden β-emitters of 3889Sr(Eβmax=1463 KeV) and 61147Pm(Eβmax=223 KeV) are investigated. Also the effect of the nuclear charge and the β-endpoint energy on IB process is investigated. As a result a good agreement between experiment and calculations of modified theory suggested by Konopski and Uhlenbeck was observed in a wide range of energy. Also it was observed that the Coulomb effect on IB process is higher in isotopes of higher values of nuclear charge (Z), and lower values of the β-endpoint energy Eβmax.

Research Highlights
► Internal Bremsstrahlung (IB) emitted during the β-decay is a phenomenon that provides us with information on the properties of nuclear states and a means of testing basic features of the theory of weak interactions. It has been a subject for any investigations both theoretical and experimental. Moreover, the Bremsstrahlung has been useful tool in scientific technical, and medical applications.
► In addition, a new trial of theoretical calculations was carried out, by applying the shape correction factor (C1), suggested by Konopski and Uhlenbeckfor the first-forbidden β-transition to the theory of Nilsson (where in Nilsson's theory the Coulomb correction factor was considered in a more refined manner than other theories). It is called Modified KUB (M.KUB) theory. As a result, a good agreement between experimental results and the M.KUB calculations was observed in a wide range of energy.
► It is suggested that if there is a global theory taking into consideration the effects of Coulomb charge, degree of forbiddances of β-decay, and consequently the “detour transitions” accompanying forbidden β-decay, we could observe a good agreement between experiment and theory.