Radio-frequency spectrum of metastable N₂(A ³∑ _u⁺). I. Magnetic hyperfine and electric quadrupole constants

Measurements have been made of the rf spectrum of metastable N 2(A 3∑u+) by the molecular beam magnetic resonance method. Transitions obeying selection rules ΔF=0, ΔMF = ±1, were observed in states with quantum numbers (N, J, F) equal to (0, 1, 2), (0, 1, 1), (1, 2, 1), (1, 2, 2), (1, 2, 3), (2, 1, 1), and (2, 3, 2). The theoretical basis of this spectrum is presented in detail and used to derive hyperfine constants and the following molecular averages: Fermi contact: ∑′ 1/2 〈δ(rai) 〉φ = (2.7±0.4) ×1023 cm -3, Electron-nuclear dipolar: ∑′ 1/2 〈(r ai-3(3 cos2θai-1) 〉φ = (-4.3±0.4) ×1024 cm -3, Quadrupole coupling: e2q0Q/h= -1.8±1.0 MHz (primes indicate that the summations are to be carried out over only the unpaired electrons).