Electron impact excitation studies of unstable atomic species

The polarization of Balmer-α radiation excited in collisions of electrons with atomic hydrogen is presented for an electron energy range from threshold to 1000 eV. Measurements are in good agreement with calculations carried out using either convergent-close-coupling or R-matrix with pseudo-states approaches. Cascade is demonstrated to have a significant effect. Balmer-α excitation function data are also presented. A previous measurement of the polarization of Balmer-α following dissociative excitation of H₂ by electrons is confirmed and extended.; The electron impact excitation spectrum of atomic and molecular nitrogen in the VUV range (800 Å–1800 Å) is presented. The excitation functions of the 1135 Å and the 1200 Å transitions are obtained. About 5% of nitrogen molecules are dissociated using a microwave discharge source and a mixture of 95% helium and 5% nitrogen gases. Other lines proved to have too small an emission cross section for the electron impact excitation process on atomic nitrogen. Thus the 1243 Å, 1494 Å, 1745 Å N lines and the 1085 Å N+ line could not be studied using the small dissociation fractions obtained in the present work.; Electron impact excitation of fluorine and sulfur atoms is presented. The spectrum of Sulfur Hexafluoride (SF₆) in the VUV range from 800 Å–1700 Å is recorded. A 70% dissociation fraction was obtained using the microwave discharge unit with SF₆ and He targets. The absolute emission cross section for the 807 Å fluorine transition is found to be 2.21 ± 1.20 × 10−19 cm 2 at 200 eV electron energy. As for sulfur, the absolute emission cross section for the 1474 Å transition is 2.46 ± 1.38 × 10−19 cm2 at 95 eV and for the 1667 Å transition is 1.87 ± 1.31 × 10−19 cm 2 at 85 eV.