Absolute differential and integral electron excitation cross sections for atomic oxygen, 8, The ³P → 5So transition (1356 Å) from 13.9 to 30 eV

The absolute direct excitation cross section of the 9.14 eV O I ³ P → 5 S o transition (1356 Å) has been measured from 13.9 to 30.0 eV incident energy. The measurement was carried out by comparing the 9.14 eV 5 S o signal to the 9.51 eV ³ S o signal and using the known ³ P → ³ S o transition cross section for normalization. The differential cross sections (DCS) peak near 60° scattering angle and generally decrease both at very small and large angles although the 13.9 eV DCS is nearly isotropic. The DCS values were integrated to give integral cross sections (ICS) at the various incident energies. The result for the peak of the cross section near 15 eV was 3 × 10 −18 cm² (±40%), in excellent agreement with the calculations of Julienne and Davis (1976). However, the ICS was significantly more sharply peaked in energy than the theoretical result. The results along with previous measurements of the ³ P → 5 P transition direct excitation cross section and total emission cross section experiments are consistent with a maximum value of the total 1356 Å emission cross section at the peak of 9–12 × 10 −18 cm².