Forbidden Band Systems in Nitrogen. III. The Y 3Σu—←X 1Σg+ System in Absorption

Abstract

Four bands of the Y ³Σ_u^—←X ¹Σ_g⁺ system of nitrogen have been observed in absorption in a path of 3.4 meter‐atmospheres at 1518 A (0–0), 1484 A (1–0), 1453 A (2–0) and 1423 A (3–0). These bands consist of an unresolved Q branch (^QQ, ^QP, ^QR), and ^SR and ⁰P branches. From a comparison of the experimental and calculated intensity distribution, it is shown that the upper state is ³Σ_u^— rather than the alternative assignment of ³Δ_u. It is further shown that the Y ³Σ_u^— state is identical with the upper state of certain infrared bands recently found in the active nitrogen afterglow. Those bands are thereby identified as Y ³Σ_u^—→B ³Π_g. The upper state was designated ``Y'' by Kistiakowsky and Warneck. The constants of Y ³Σ_u^— as obtained here are: ω_e=1517.6₉ cm^—1; ω_ex_e=12.2₂ cm^—1; B_e=1.472 cm^—1; α_e=0.016₁ cm^—1; T₀₀=65850_.6 cm^—1; r_e=1.278₈ A. The transition Y ³Σ_u^—←X ¹Σ_g⁺ receives intensity from perturbations of Y ³Σ_u^— by ¹Σ_u⁺ and ¹Π_u states lying at higher energies.