Potential energy curves for the X(1)Sigma(g)(+) ground state and Omega = 0(+)1, 1(u) valence states and dipole moments for the 0(u)(+), 1(u) -X transitions are obtained in an ab initio configuration interaction study of Cl-2 including spin-orbit coupling. In contrast to common assumptions, it is found that the B(3)Pi(0+u)-X transition moment strongly depends on internuclear distance, which has an important influence on the Cl-2 photodissociation. Computed energy curves and transition moments are employed to calculate the A, B, C A<--X extinction coefficients, the total spectrum for the first absorption band, and the Cl*(P-2(1/2))/Cl(P-2(3/2)) branching ratio as a function of excitation wavelength. The calculated data are shown to be in good agreement with available experimental results. (C) 2004 American Institute of Physics.