  We present a new theoretical method to treat the atom diatom radiative
association within a time independent approach. This method is an adaptation of
the driven equations method developed for photodissociation. The bound states
energies and wave functions of the molecule are calculated exactly and used to
propagate the overlap with the initial scattering wave function. In the second
part of this paper, this approach is applied to the radiative association of
the N2H- anion. The main features of the radiative association cross sections
are analysed and the magnitude of the calculated rate coefficient at 10 Kelvin
is used to discuss the existence of the N2H- in the interstellar medium which
could be used as a tracer of both N2 and H-.
