  We report on the existence of temperature induced negative differential
conductivity (NDC) for electrons in gaseous nitrogen. The important role of
superelastic rotational collisional processes in this phenomenon is
highlighted. A model cross-section set, utilised to ensure an accurate
treatment of superelastic processes and achieve thermal equilibrium is
detailed, and used to illustrate the role of de-excitation processes in NDC.
The criterion of Robson [1] for predicting the occurance of NDC using only
knowledge of the collisional cross-sections is utilised for both the model
system and N_{2}. We also report on the impact of anisotropy in the very low
threshold scattering channels on the transport coefficients, examine the
Frost-Phelps finite difference collision operator for the inelastic channel, in
particular its neglect of recoil, and assess other assumptions utilised in
existing Boltzmann equation solvers. We discuss the numerical challenges
associated with low reduced electric field calculations, and detail an
alternative representation of the elastic and inelastic collision operators
used in Boltzmann equation solutions that enforce conservation of number
density. Finally, new experimental measurements of the drift velocity and the
Townsend ionisation coefficient for an electron swarm in are reported from a
pulsed Townsend experiment. The self-consistency of the utilised cross-sections
is also briefly assessed against these results.
