  Low-energy inelastic collisions with neutral hydrogen atoms are important
processes in stellar atmospheres, and a persistent source of uncertainty in
non-LTE modelling of stellar spectra. We have calculated and studied excitation
and charge transfer of C i and of N i due to such collisions. We used a
previously presented method that is based on an asymptotic two-electron linear
combination of atomic orbitals (LCAO) model of ionic-covalent interactions for
the adiabatic potential energies, combined with the multichannel Landau-Zener
model for the collision dynamics. We find that charge transfer processes
typically lead to much larger rate coefficients than excitation processes do,
consistent with studies of other atomic species. Two-electron processes were
considered and lead to non-zero rate coefficients that can potentially impact
statistical equilibrium calculations. However, they were included in the model
in an approximate way, via an estimate for the two-electron coupling that was
presented earlier in the literature: the validity of these data should be
checked in a future work.
