Generalized Oscillator Strength of the à ← X̃ Transition of Ammonia

The generalized oscillator strength for the $\mathrm{Ã\hspace{0.17em}\leftarrow \hspace{0.17em}X̃}$ transition in NH₃ has been determined by electron impact spectroscopy. A high‐resolution spectrometer was used to measure the intensity of the strongest vibrational peak, 6.390 eV, relative to the elastic scattering. These intensity ratios were used to determine inelastic cross sections at electron kinetic energies of 300, 400, and 500 eV and scattering angles between 2°–7°. These inelastic cross sections were put on an absolute basis by comparison with absolute elastic cross sections for NH₃, measured by Bromberg (unpublished work). The generalized oscillator strength, integrated over all vibrational terms of the transition, was extrapolated to zero momentum change for comparison with optical values. The extrapolated oscillator strength is 0.069₆ ± 0.006.