Observed spectra (solid line) of CH₂ND (N_KaKc = 10_{2 8} ← 9_{1 9}). The nitrogen hyperfine structure (quadrupole coupling) was partially resolved. They are completely decomposed into two spectral components (overlapping of F = 11–10 and 9–8 and F = 10–9 components) shown as dotted lines, each of which has been simulated by giving appropriate parameters to make the second derivative of Voigt line shapes. The residual between observed and simulated spectra was satisfactorily small, as shown at the bottom of the figure. The spectrum was recorded by integrating 30 scans with a 0.5 Hz repetition rate and a 1 ms time constant of the lock-in amplifier.