[Ifeffit] Core-hole Lifetimes in Hephaestus 0.9.26

[Matt Newville]

I believe it is using (or intends to use)

    lifetime = hbar /gamma

which is what Krause et al give.  With gamma = 0.2 eV, and hbar ~=
4.13567e-15 eVs, then lifetime is ~20fs.
Maybe I'm missing something more subtle?  FWIW, these reported numbers for
gamma in eV are described by Krause et al as "FWHM".

--Matt


On Mon, Sep 28, 2020 at 1:13 PM Daniel Przyrembel <
daniel.przyrembel at fu-berlin.de> wrote:

> Hi Matt,
>
> Thanks for the quick reply!
> However, I seem to not have made clear my concern...
>
> The widths in energy (eV) are fine.
>
> However, in "Hephaestus", the "souped-up periodic table for the X-ray
> absorption spectroscopist", these level widths in energy (eV) are also
> given as equivalent lifetimes (in fs), however incorrectly: A level width
> of ~0.2 eV in fact corresponds to a lifetime of ca. 3 fs, not ~30 fs as
> given there.
>
> Those lifetimes shown in Hephaestus all seem to be off by a general factor
> of 10. I guess that is just the energy width/lifetime conversion gone
> slightly wrong...
> I imagine I'm not the only one using Hephaestus as a convenient tool to
> look stuff up quickly, so I thought it might be useful to point out this
> flaw.
>
> Just to make sure, I have again imported the xraydb: That has not changed
> Hephaestus' behavior in terms of the lifetime info (I'm using the latest
> 64-bit version on Windows).
>
>
> > Hi Daniel,
> >
> > Thanks - that does seem wrong.  FWIW, Larch uses XrayDB which uses
> > corehole
> > widths from Krause and Oliver for Z>10 and Keski-Rahkoken nand Krause for
> > Z<10.
> > For the F K edge, this give 0.2089 eV.  For this or other core-hole
> > widths,
> > and assuming you have Python installed, try:
> >
> >   ~> pip install xraydb
> >   ~> python
> >   >>> import xraydb
> >   >>> xraydb.core_width('F', 'K')
> >   0.2089
> >
> > Or install Larch and use
> >
> >    ~> larch
> >    larch> core_width('F', 'K')
> >    0.2089
> >
> >
> >
> > On Mon, Sep 28, 2020 at 12:08 PM Daniel Przyrembel <
> > daniel.przyrembel at fu-berlin.de> wrote:
> >
> >> To Whom it may concern,
> >>
> >> I am quite sure there is a general lifetime/energy-width conversion
> >> error
> >> in Hephaestus: All core-hole lifetimes seem to come out too long by a
> >> factor of - as it seems exactly - 10:
> >> E.g. the lifetime of the F K-edge with a width of 0.25 eV is given as
> >> 25.30 fs instead of ca. 2.6 fs (width = h_bar / lifetime).
> >>
> >> This glitch was present in 0.9.25 already and, as I noticed after
> >> updating, prevails in 0.9.26. I have not tried earlier versions.
> >>
> >> Best regards,
> >>
> >> Daniel
> >>
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-- 
--Matt Newville <newville at cars.uchicago.edu> 630-252-0431
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