Elastic scattering of two ground-state N atoms

An interaction potential for an N$_{2}$(X$^{1}\Sigma_{\rm g}^{ + })$ molecule is constructed by using the highly accurate valence internally contracted multireference configuration interaction method and the largest basis set, aug-cc-pV6Z, in the valence range. The potential is used to investigate the elastic scattering of two N atoms at energies from 1.0$\times $10$^{ - 11}$ to $1.0\times 10^{ - 4}$ a.u. The derived total elastic cross sections are very large and almost constant at ultralow temperatures, and the shape of total elastic cross section curve is mainly dominated by the $s$-partial wave at very low collision energies. Three shape resonances are found in the total elastic cross sections. Concretely, the first one is very sharp and strong. It results from the $g$-partial-wave contribution and the resonant energy is $3.645\times 10^{ - 6}$ a.u. The second one is contributed by the $h$-partial wave and the resonant energy is $1.752\times 10^{ - 5}$ a.u. This resonance is broadened by those from the $d$- and $f$-partial waves. The third one comes from the $l = 6$ partial wave contribution and the resonant energy is $3.522\times 10^{ - 5}$ a.u. This resonance is broadened by those from the $g$- and $h$-partial waves. The N$_{2}$(X$^{1}\Sigma _{\rm g}^{ + })$ molecular parameters, which are determined at the current theoretical level, achieve very high accuracy due to the employment of the largest correlation-consistent basis set in the valence range.