Precision calculation of low-energy electron-impact excitation cross sections of sodium

Abstract

The collision cross sections of sodium from the ground state to the first four excited states at the incident energy ranging from 0 to 5.4 eV are calculated using the $R$-matrix method. The convergences of the cross sections are checked systematically by using four sets of high-quality target states, i.e., 5, 9, 14, and 19 physical target states. The influence of the Rydberg target states on the collision cross sections is also elucidated at higher incident energies; i.e., the amplitude of resonance structures will decrease with respect to the effective quantum number $\ensuremath{\upsilon}$ of the Rydberg target states. This result is very useful for the calculations of these cross sections at intermediate energy with finite target states by combining the partial-wave-expansion methods valid at low energy with the first Born approximation method valid at high energy, which would be of great importance in obtaining complete cross-section data for related scientific fields.