Absorption spectrum of the NO molecule. VIII. The heterogeneous (2Σ–2Π) interactions between excited states

Abstract

Heterogeneous perturbations ²E⁺ ~ ²Π of largely different magnitudes are observed with high resolution in the vacuum-ultraviolet absorption and in the infrared emission spectrum of the NO molecule. The rotational interactions between ²Σ⁺ Rydberg states and levels of the B²Π non-Rydberg state are shown to be "configurationally forbidden", but produced by the configuration interaction between the non-Rydberg levels and ²Π Rydberg states. The latter together with the ²Σ⁺ Rydberg states form p complexes. In this way the interactions display the l uncoupling in the complexes; they can be evaluated theoretically and can be analyzed fully. The cases of the strong interactions D²Σ⁺(v = 3) ~ B²Π(v = 16)and D²Σ⁺(v = 5) ~ B²Π(v = 21) and of the weaker D²Σ⁺(v = 1) ~ B²Π(v = 11), all three observed as perturbations in ε bands crossing 3 bands, are discussed in detail. It is further shown that perturbations between γ bands and β bands as well as perturbations between analogous bands of higher principal quantum number are absent, and thus the assignment of the A²Σ⁺ and E²Σ⁺ states to the s Rydberg series is confirmed.