The computed time evolution of excited electronic and nuclear:states:. of dinitrogen following a broad laser pulse excitation of the dipole allowed singlet Pi states is discussed. The computations use two complementary methods to solve the time-dependent Schrodinger equation of the molecule. The electronic evolution is described as spanning seven states, the three dipole-allowed singlet states (b,c,o(1)Pi(u)) and four triplet states (C,C',F,G(3)Pi(u)). Spin orbit coupling mixes states of the two manifolds. The computed dynamics includes the attosecond pulse single photon pumping from the electronic ground state. The ultrafast exit to the continuum from the bound states that are optically excited and the large isotope effect on this process are used as a probe of the electron dynamics as coupled to the Onset of the nuclear motion. For -'4N2-, prompt predissociation to the continuum of the repulsive C'(3)Pi(u) state is facilitated primarily by the b(1)Pi(u)(v=3)-C-3 Pi(u)(v = 9) coupling whereas for N-15(2) it is the b1 Pi(u) (v =4)-C-3 Pi(u)(v =10) coupling term. Predissociation from the F3 Pi u and G(3)Pi(u) stateS is important at the high energies because of their strong coupling to the continuum.