Abstract
Crossed beams of electrons and ions combined with fluorescence detection were used to measure the absolute cross section for electron-impact excitation of the ions to yield 186.3 nm and 185.5 nm photons from the transition. The measured cross section near the 6.7 eV threshold energy is about and some resonance structure near threshold is indicated. Total relative uncertainties are typically about 6%, to be combined with an 11% absolute calibration uncertainty. Total uncertainties at high confidence level (90%) are around 20%, using a coverage factor of 1.7. Comparisons made with various theoretical calculations, specifically distorted wave and nine-state close coupling, show better agreement of experimental values with distorted wave calculations, with the measured values being higher near threshold than the most recent close-coupling calculations.
- Received 19 April 2002
DOI:https://doi.org/10.1103/PhysRevA.66.032706
©2002 American Physical Society