Collision strength (${\Omega }_{ji}$)

A dimensionless atomic collision measure used to parameterize electron-impact transition coefficients. In the Maxwellian approximation used here, $q_{ji}=8.6\times 10^{-12}{\Omega }_{ji}/(g_j\sqrt{T_e})$ in ${\mathrm{m}}^3{\mathrm{s}}^{-1}$, and detailed balance fixes the excitation coefficient. Its value and temperature dependence encode atomic scattering physics beyond the elementary Boltzmann factor.