  Efforts to benchmark astrophysical observations with X-ray laboratory
measurements have been stymied by observed and measured differences of up to a
factor of two in the ratio '3s/3d' of Fe XVII lines at ~17 \AA and ~15 \AA
respectively. Using the electron distribution function (EDF) as a new physical
parameter, we compute the Fe XVII line ratios and account for these
differences. Based on large-scale relativistic close coupling calculations
using the Breit-Pauli R-matrix method, revealing the precise effect of
resonances in collisional excitation, we employ collisional-radiative models
using cross sections convolved with both the Gaussian and the Maxwellian EDF.
Comparison with astrophysical observations and laboratory measurements
demonstrates that (a) the 3s/3d line ratio depends not only on the EDF but also
on the electron temperature/energy of the source, (b) plasma conditions in
experimental measurements and astrophysical observations may be quite
different, and (c) departure from a Maxwellian should manifest itself in, and
be used as a diagnostics of, particle distributions in plasmas.
