Nitrogen Quadrupole Coupling Measurements on ON-NO₂ Using the Flygare-Balle Pulsed-Beam Spectrometer

High-resolution measurements of the 1₀₁ ← 0₀₀, 2₁₂ ← 1₁₁, 2₀₂ ← 1₀₁, 2₁₁ ← 1₀, 3₁₂ ← 3₁₃, and 4₁₃ ← 4₁₄ transitions in the ON-NO₂ complex were made by using a pulsed-beam, Fourier transform microwave spectrometer. Nearly all hyperfine structure components were resolved on observed transitions except for the 2₀₂ ← 1₀₁ group. The quadrupole coupling tensors in the principal axis system were determined for both nitrogen atoms. The nitrogen quadrupole coupling components for the NO group are eQq_aa = −1.7766 ± 0.0037 MHz and eQq_bb = 0.0585 ± 0.0021 MHz. For the NO₂ group eQq_aa = −0.5260 ± 0.0035 MHz and eQq_bb = −4.1941 ± 0.0018 MHz. The rotational constants obtained are A = 12412 ± 22 MHz, B = 4226.530 ± 0.012 MHz, and C = 3152.966 ± 0.012 MHz. Rotational transition frequencies and estimates of spin-rotation interaction strengths are given. The observed quadrupole coupling strengths are substantially different from those observed for the free NO and NO₂ molecules.