[Ifeffit] Core-hole Lifetimes in Hephaestus 0.9.26

[Matt Newville]

Hi,

Ah, Krause et al *do* use hbar, not h, so yeah With gamma = 0.2 eV, and h
~= 4.13567e-15 eVs (hbar ~ 6.582e-16 eVs), then lifetime is ~3 fs.

That is probably the mistake that hephaestus is making too.  FWIW, we are
not currently, but could be reporting core-level widths and lifetimes at
https://xraydb.xrayabsorption.org/


On Mon, Sep 28, 2020 at 1:37 PM Matt Newville <newville at cars.uchicago.edu>
wrote:

> 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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>>
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>
>
> --
> --Matt Newville <newville at cars.uchicago.edu> 630-252-0431
>


-- 
--Matt Newville <newville at cars.uchicago.edu> 630-252-0431
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