We report integral cross sections (ICSs) for electron impact excitation of the A 3 + u , B 3 g , W 3 u , B 3 − u , a 1 − u , a 1 g , ω 1 u , C 3 u , E 3 + g and a 1 + g electronic states of N 2 . The present data, for each state, were derived at five incident electron energies in the range 15-50 eV, from the earlier crossedbeam differential cross section (DCS) measurements of our group. This was facilitated by using a molecular phase shift analysis technique to extrapolate the measured DCSs to 0 • and 180 • , before performing the integration. A comprehensive comparison of the present ICSs with the results of earlier experimental studies, both crossed beam and electron swarm, and theoretical calculations is provided. This comparison clearly indicates that some of the previous estimates for these excited electronic-state cross sections need to be reassessed. In addition, we have used the present ICSs in a Monte Carlo simulation for modelling the behaviour of an electron swarm in the bulk of a low current N 2 discharge. The macroscopic transport parameters determined from this simulation are compared against those measured from independent swarm-based experiments and the self-consistency of our ICSs evaluated.

We find resolved interstellar O K, Ne K, and Fe L absorption spectra in the Chandra Low Energy Transmission Grating Spectrometer spectrum of the low mass X-ray binary X0614+091. We measure the column densities in O and Ne, and find direct spectroscopic constraints on the chemical state of the interstellar O. These measurements probably probe a low-density line of sight through the Galaxy and we discuss the results in the context of our knowledge of the properties of interstellar matter in regions between the spiral arms.

No abstract

Photoionization of atomic oxygen near the 1s −1 threshold is reinvestigated by including a more extensive inner-shell configuration interaction description, and by using an optical potential to account for autoionization to the infinite number of singly excited O + continua. These new theoretical results remove the earlier discrepancies between theory and experiment.