# User talk:Evgeny

## Stark spectroscopy

Hi Evgeny, I just saw that I removed your freshly added disambig to Stark spectroscopy. It may be that you were still working on the page, but as it is now, it is surely not a disambig page. I don't really know much about this (I was running a cleanup run on a list of strange stubs), so feel free to edit the article to your liking (will keep an eye on it, I might learn something). Sorry 'bout this. --Dirk Beetstra T C 13:57, 21 August 2006 (UTC)

## Bremsstrahlung

May I ask what is "BS" about Griffith's treatment of bremsstrahlung? I'm pretty sure the difference between Griffiths' and Diver's angular power distributions is that Diver's is valid in the rest frame of the moving particle, whereas Griffiths gives the radiation that an observer would see when watching a particle move with speed v subject to acceleration a. The latter is arguably more useful, and is certainly not "BS" !! I would suggest reverting the edit, except the relativistic generalization is useful. I think some combination of the two versions of this section would be best. Rotiro (talk) 20:01, 11 February 2008 (UTC) I wish I had my texts with me, but I don't. Consider consulting Landau & Lifshitz; that's a fairly authoritative source. Rotiro (talk) 20:10, 11 February 2008 (UTC)

See the continuing discussion here . Rotiro (talk) 12:31, 12 February 2008 (UTC)

## Update on fermi energy vs fermi level

I looked it up my undergrad textbook (Ashcroft and Mermin), and they too distinguish Fermi level from Fermi energy. So as far as I can tell, "Fermi level" is completely unambiguous, and "Fermi energy" is the only one where there are different definitions. (Do you agree?) I'm going to change my edit at electronic band structure accordingly...no need to bring up "fermi energy" at all. Thanks again for helping me learn about this! :-) --Steve (talk) 04:16, 29 March 2009 (UTC)

It's even worse than I thought...see my section Fermi level#Terminology for example...the two opposite definitions of chemical and electrochemical potentials is especially unfortunate. :-) --Steve (talk) 08:27, 29 March 2009 (UTC)
Yes, there is a lot of confusion and ambiguity in the solid-state literature. But, of course, we can avoid all this in Wikipedia by deciding on something and sticking to it. My preference is "Fermi energy" (at T=0) and "chemical potential". The problem with "Fermi level" is that one still uses for it the same symbol ${\displaystyle E_{F}}$ as for the Fermi energy... --Evgeny (talk) 13:11, 30 March 2009 (UTC)

## Articles for deletion nomination of Grace (plotting tool)

I have nominated Grace (plotting tool), an article that you created, for deletion. I do not think that this article satisfies Wikipedia's criteria for inclusion, and have explained why at Wikipedia:Articles for deletion/Grace (plotting tool). Your opinions on the matter are welcome at that same discussion page; also, you are welcome to edit the article to address these concerns. Thank you for your time.

I disagree but am not going to burn time fighting for it.--Evgeny (talk) 14:11, 20 June 2009 (UTC)
No need, there are now some sources included in the article which demonstrate its notability. It's being kept :) Papa November (talk) 16:07, 24 June 2009 (UTC)

## Atomic_units

Hi. some years ago you moved E_h, hartree energy from fundamental units to derived units. I agree that at that time the table was redundant (not all listed could be fundamental), but for some reason you choosed to remove Hartree Energy instead of the "Coulomb force constant". Do you remember why was that? The article doesn't cite any reference for this choice, on the contrary, BIPM at http://www.bipm.org/en/si/si_brochure/chapter4/4-1.html says that

" ... Similarly, in the a.u. system, any four of the five quantities charge, mass, action, length, and energy are taken as base quantities. The corresponding base units are the elementary charge e, electron mass me, action , Bohr radius (or bohr) a0, and Hartree energy (or hartree) Eh, respectively. In this system, time is again a derived quantity and the a.u. of time a derived unit, equal to the combination of units /Eh. Note that a0 = alpha/(4piRinfinity), where alpha is the fine-structure constant and Rinfinity is the Rydberg constant; and Eh = e2/(4piepsilon0a0) = 2Rhc0 = alpha2mec02, where epsilon0 is the electric constant and has an exact value in the SI. ..."

that is, energy (Hartree) is a base unit of the system. However for some reason, the article insists that the "electric constant" is a base unit, why is this? isn't it better to agree with BIPM?

--Alfredo 04:20, 7 May 2010 (UTC) —Preceding unsigned comment added by Alfredo.correa (talkcontribs)

Hi. Mathematically, there is indeed a freedom of choosing the base units. From the physical point of view, it makes more sense to base on the physical constants as much as possible. Please note that in the article, I used "fundamental units" instead of "base units". So while one can express the electric constant using the hartree energy etc, this is rather awkward (the electric constant is precisely defined in SI). Evgeny (talk) 16:34, 9 May 2010 (UTC)

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