MICROSCOPIC SHELL-MODEL AND CLUSTER-MODEL CALCULATIONS OF THE C-13-]C-12-8-]BE-7+P VERTEX CONSTANTS(N AND B)

Vertex constants are calculated with an effective nucleon-nucleon inte raction and translation-invariant harmonic-oscillator shell-model wave functions consistently obtained with the same interaction. Such calcu lations are presented for the C-13 --> C-12 + n vertex constant for wh ich an accurate experimental value is available, and for the B-8 --> B e-7+p vertex constant, which is crucial for the determination of the B e-7(p,gamma)B-8 reaction at astrophysical energies. Calculations confi rm the strong sensitivity of vertex constants to the choice of the eff ective nucleon-nucleon interaction. A comparison of vertex constants o btained in the shell-model approach and in microscopic two- and three- cluster models with identical nucleon-nucleon potentials shows that th e main contribution to the cluster-model vertex constants comes from t he shell-model parts of the cluster-model wave functions. The reliabil ity of model calculations of the 7Be(p,gamma)B-8 astrophysical S facto r is discussed. (C) 1997 Elsevier Science B.V.