Rydberg states of the nitrogen moleculea)

Rydberg states (^1,3Σ_g⁺, ^1,3Σ_u⁺, ^1,3Π_g, and ^1,3Π_u) of N₂ that converge to the N₂⁺ (X ²Σ_g⁺) ion have been calculated. The core orbitals are taken as those of the free N₂⁺(X ²Σ_g⁺) ion. The Rydberg electron wave functions are expanded by one-center basis functions which are solution of an electron moving in a sphericalized potential of the N₂⁺(X ²Σ_g⁺) ion. This expansion converges rapidly since the basis functions are already a fairly good representation of the Rydberg states especially for the higher ones. The use of one-center expansion allows us to examine the mixing of the basis functions of different angular-momentum quantum number l in the Rydberg states which is found to be generally small. Energy levels are reported for singlet and triplet Rydberg states of the Σ and Π types (Λ=0,1) with l from 0-9 and n through 11. The Rydberg levels with l≥4 are entirely hydrogenic. For lower l the quantum defect varies significantly with n within a given l series. Also a wide range of quantum defect is found for different states. Transitions among the various Rydberg series produce a very rich spectrum in the long-wave infrared region.