The potential energies of nitrogen atoms interacting with helium and argon atoms are determined and the rates of thermalization of initially energetic nitrogen atoms traversing bath gases of helium and argon atoms are obtained. The C6 dispersion coefficients are determined to be 5.79 a.u. for N-He and 39.42 a.u. for N-Ar. Quantum mechanical calculations of the differential scattering cross-sections are carried out and used to find solutions to the kinetic Boltzmann equations. The rates of thermalization are compared with experiments on the translational energy relaxation of nitrogen atoms produced by the photolysis of NO2. The accuracy of the hard sphere approximation in interpreting the data is explored, and found to be satisfactory with hard sphere cross-sections of 1.50 10-15 cm2 for helium and 1.98 10-15 cm2 for argon.