NUCLEAR VERTEX CONSTANTS FOR THE VIRTUAL-DISINTEGRATION REACTIONS LI-7-]ALPHA-7-]ALPHA+HE-3 AND FOR THE DIRECT-RADIATIVE-CAPTURE PROCESSES T(ALPHA, GAMMA)LI-7 AND HE-3(ALPHA, GAMMA)BE-7 AT ASTROPHYSICAL ENERGIES(T AND BE)

The nuclear vertex constants for the virtual-disintegration processes Li-7 --> alpha + t and Be-7 --> alpha + He-3 are calculated in an alph a-cluster model that employs a potential involving forbidden states. T he results are compared with the values extracted from the measured an d calculated astrophysical S factors of the processes t(alpha, gamma)L i-7 and He-3(alpha, gamma)Be-7 at extremely low energies. Potentials o f alpha t and alpha(3)He interaction that closely reproduce nuclear ve rtex constants extracted from experimental data are found.