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

Vibrationally elastic ( Delta v=0) scattering and vibrational excitation of H 2 S by electron impact has been studied for collision energies up to 10 eV in a closed-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 2 A 1 symmetry. In the shape resonance the absolute value of the total integral cross section for vibrational excitation has been found to exceed 10 -15 cm 2 , which is about 30% of the vibrationally elastic one.