Hi Matt,
Well, independent of what Krause et al. have done, the correct uncertainty
relation between core-hole widths as FWHM (full width at half maximum) and
the lifetime is
lifetime = h_bar / FWHM
from the corresponding half-width (HWHM) expression
HWHM x lifetime >= h_bar / 2
Again, I just stumbled upon this when using Hephaestus, and the lifetimes
were all oddly "long".
The above relations are often garbled up due a HWHM-FWHM mix-up (the HWHM
being the "spread" of the Cauchy/Lorentz/Breit-Wigner distribution towards
higher and lower energy around the center etc.) as well, giving factor of
two errors...
Yeah, I think most of us in the X-ray spectroscopy community think in eV and not in fs. ;) But it would obviously be better to report those lifetimes better too.
I don't really have a strong feeling on whether reporting FWHM or HWHM (or sigma, for non-Lorentzians), but consistency is good. For sure, the values from Krause et al are well-used in the X-ray spectroscopy community. But, well should that 'lifetime' be a 1/e value?
--Matt