Abstract
Absolute emission cross sections for electron-impact excitation of the and terms of have been measured from below threshold to about 790 eV () and 388 eV () using the crossed-charged-beams technique. Both transitions have the abrupt onset at threshold characteristic of positive-ion excitation. The cross section shows considerable structure in the interval from threshold to near 20 eV, above which it falls off smoothly. Agreement with five-state close-coupling theory is excellent below 100 eV when cascading is included in the theory. Above 100 eV, the data lie above the theory. The peak value of the cross section is 9.4× essentially at threshold, while the peak value of the cross section is about 0.47× . The net linear polarization of the emission was measured (unresolved from the cascading transition), and these data were used to correct the cross-section data for anisotropy of the emitted light. The effective lifetime of the level was measured by observing exponential decay of the 589.6-nm photons resulting from its decay.
- Received 26 May 1981
DOI:https://doi.org/10.1103/PhysRevA.25.681
©1982 American Physical Society