2008 Articles

Electron-Impact Ionization of Be-like C III, N IV, and O V

Fogle, M.; Bahati, E. M.; Bannister, M. E.; Vane, C. R.; Loch, S. D.; Pindzola, M. S.; Ballance, C, P,; Thomas, R. D.; Zhaunerchyk, V.; Bryans, P.; Mitthumsiri, W.; Savin, Daniel Wolf

We present recent measurements of absolute electron-impact ionization cross sections for Be-like C III, N IV, and O V forming Li-like C IV, N V, and O VI. The measurements were taken using the crossed-beams apparatus at Oak Ridge National Laboratory. A gas cell beam attenuation method was used to independently measure the metastable fractions present in the ion beams. The measured ionization cross sections were compared with calculations using the R-matrix with pseudostates and distorted-wave theoretical methods. Best agreement is found with the R-matrix with pseudostates cross sections results that account for the metastable fractions inferred from the gas attenuation measurements. We present a set of recommended rate coefficients for electron-impact single ionization from the ground state and metastable term of each ion.