Differential scattering experiments for e-H2S collisions in the low-energy range

Vibrationally elastic scattering and vibrational excitation of H2S by electron impact has been studied for collision energies up to 10 eV in a crossed-beam experiment. In the vibrationally elastic scattering the cross sections show pronounced forward scattering and a steep increase towards small energies, characterising the influence of the direct dipole process. In contrast, the vibrational excitation is clearly dominated by resonance processes. The excitation function exhibits a narrow peak close to threshold, which is attributed to the final-state interaction of the scattering electron in the dipole field and a strong shape resonance at about 2.3 eV of 2A1 symmetry. In the shape resonance the absolute value of the total integral cross section for vibrational excitation has been found to exceed 10-15 cm2, which is about 30% of the vibrationally elastic one. (author)