ИСТИНА

Asymptotic normalization coefficients (ANC) determine the asymptotic behavior of nuclear wave functions in binary channels at distances between fragments exceeding the radius of nuclear interaction [1]. In terms of ANCs, the cross sections of peripheral nuclear transfer reactions are parameterized. ANCs are of particular importance for nuclear astrophysics. They determine the overall normalization of cross sections of radiative capture reactions at astrophysical energies [2]. Unlike binding energies, ANCs cannot be directly measured. To determine them on the basis of experimental data, a certain theoretical analysis is required. In particular, the values of ANCs can be extracted by comparing the absolute values of experimental cross sections of nuclear transfer reactions with theoretical ones, calculated within the framework of the distorted wave Born approximation. Some other methods for determining ANCs from experimental data and reactions are described in [3]. In the present work, the method of finding the values of ANCs is proposed based on the analytic continuation of the R-matrix that describes the elastic nuclear scattering into the unphysical region of the negative energy of collision (E <0). The formula is derived, expressing the partial-wave scattering amplitude through the R-matrix and modified Coulomb functions. This formula allows, when continuing the amplitude to the region E <0, to overcome difficulties associated with irregular behavior of the scattering amplitude near E = 0 if the Coulomb interaction is present. The proposed method is used to determine the ANC for the channel 16O → α+12C.