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The oscillator strengths and integral cross sections of the valence-shell excitations of HCl have significant applications in the studies of planetary atmospheres and interstellar gases. In the present work, the generalized oscillator strengths of the valence-shell excitations of HCl have been measured at an incident electron energy of 1500 eV and an energy resolution of 70 meV, and their momentum transfer dependence behaviors have been elucidated. It is observed that the generalized oscillator strength ratios of the b3Π1(ν' = 0) state to the C1Π(ν' = 0) state are a constant and independent of the squared momentum transfer, and this typical behavior in the momentum space is explained by the intraconfiguration mixing of the b3Π1 and C1Π states due to the spin-orbital interaction. The optical oscillator strengths of the valence-shell excitations have been obtained by extrapolating the generalized oscillator strengths to the limit of zero squared momentum transfer. The present optical oscillator strengths give an independent cross-check to the previous experimental and theoretical results, and it is found that most of the photoabsorption measurements are limited by the line saturation effect. The integral cross sections of the valence-shell excitations of HCl have been obtained systematically from the threshold to 5000 eV with the aid of the BE-scaling method.

The valence-shell excitations of hydrogen sulfide have been studied by fast electron impact at a collision energy of 1.5 keV and an energy resolution of about 70 meV. By analyzing the variations of intensity and shape of the feature in the range of 5.0-7.5 eV at different scattering angles, the excitation energy of 5.85 ± 0.01 eV and the line width of 0.80 ± 0.01 eV of the 3b21A2 state have been determined. The generalized oscillator strengths of the valence-shell excitations in the energy range of 5.0-9.2 eV of hydrogen sulfide have been determined from the measured spectra. The corresponding optical oscillator strengths have been obtained by extrapolating the generalized oscillator strengths to the limit of zero squared momentum transfer. The integral cross sections have also been systematically determined from the threshold to 5000 eV by means of the BE-scaling method. The presently obtained oscillator strengths and integral cross sections have significant applications in the studies of planetary atmospheres and interstellar gases.

The generalized oscillator strengths of the valence-shell excitations from the ground state to 3p5(4s, 4s', 4p, 4p', 3d, 3d', 5p, 5p', 5s, 4d) of argon have been determined at an incident electron energy of 1500 eV and an energy resolution about 90 meV. The accuracy of the present generalized oscillator strengths is improved by the adopted relative flow technique. The comprehensive comparison of the present results with the previous experimental and theoretical ones shows that the first Born approximation is satisfied in the lower squared momentum transfer region for the electric dipole excitations, while the deviations from the prediction of the first Born approximation and the inelastic X-ray scattering measurements near the minimum and in the larger K2 region are obvious, which can be attributed to the failure of the first Born approximation in this K2 region. The invalidity of the first Born approximation has also been observed for the electric monopole transitions even at a high impact electron energy of 2500 eV.

The vibrationally resolved generalized oscillator strengths of the first and strongest singlet excitation AA2″1← X1A1 of ammonia have been determined at an impact electron energy of 1500 eV with an energy resolution of 80 meV. The comprehensive comparison of the present results with the previous experimental and theoretical ones shows that the high-energy limit, where the first Born approximation holds, has been reached at an impact electron energy of 1500 eV in K2 1 a.u. even at 1500 eV. It is also observed that the minimum position of the generalized oscillator strength of the vibronic state shifts toward the larger squared momentum transfer with the increasing vibrational quantum number. By extrapolating the generalized oscillator strength to the zero momentum transfer, the optical oscillator strength of the AA2″1 state has been obtained, which gives an independent cross check to the previous results. The integral cross sections of the AA2″1 state have been obtained systematically from the threshold to 5000 eV with the aid of the BE-scaling method.