Subject: orbitals and reality

From: Eric Scerri <scerri(at)chem.ucla.edu>
Date: Sat, 22 Jan 2005 14:47:15 -0800

The discussion has been very interesting.  I have worried about these 
issues before and have published two papers specifically addressing 
the question of observation or otherwise of orbitals. Both can be 
accessed on my UCLA web page.

One is addressed to chemical educators and the other to philosophers 
of science.

http://www.chem.ucla.edu/dept/Faculty/scerri/

See entries 73 and 90 for the educational question and 81 for the 
article to the Philosophy of Science Association.  # 73 is cited in 
the textbook by Zumdahl in the section on orbital models that was 
reproduced on this list a few days ago.

These articles were prompted by the claims in 1999, including a front 
page feature in Nature Magazine that orbitals had been directly 
observed.  I have been too busy to follow all the details of the 
recent claim but I cannot help thinking that just as in 1999 there is 
a certain amount of hype going on.

This was more or less confirmed a few days ago when I learned from 
the discussion on this list that Villneuve actually admits that they 
deliberately used provocative language in their claims.

I too wrote to Stepelfeld and Villneuve and sent them copies of my 
articles, asking them to try to explain why this recent observation 
is any different from that of 1999, in theoretical/philosophical 
terms.  The response I received from Stepelfeld is identical to the 
one that was posted on this list a few days ago.  Villneuve has yet 
to respond.

The claim would only be worthy of drama and front page news if 
orbitals had indeed been observed, which we all know in advance 
cannot ever happen.

How is it that we have never heard again from the Arizona State team 
that observed orbitals in copper oxide?

Would it be possible for Villneuve et al. to observe orbitals in an 
atomic system in order to disentangle any complications that might 
occur because one is dealing with a molecule in N2?

Could they or somebody else turn their technique to atomic hydrogen?

Could anyone perform some experiments which are specifically aimed at 
imaging orbitals rather than just mentioning it in the course of an 
article to Nature in the knowledge that it will make a splash?

The question of whether one could speak meaningfully of an empty 
orbital is interesting.  Well of course we can speak of it, just as 
we can speak of unicorns etc.  That does not make them exist.

What I mean is that the whole notion of electrons IN orbitals is 
something of a confusion in conceptual terms.  Admittedly the putting 
of electrons in orbitals is very useful as a book-keeping device just 
as it is very useful mathematically to consider the occupation of 
certain orbitals and not others in calculations, sometimes even with 
fractional occupations.  But if one wants to picture the situation 
conceptually perhaps an orbital just IS one or more electrons in the 
sense of wave-particle duality.  To return to thinking of electrons 
as particles IN an orbital (probability waves) maybe a failure to 
bite the bullet of wave-particle duality in conceptual terms.

regards,
eric scerri

-- 

Dr. Eric Scerri ,
UCLA,
Department of Chemistry & Biochemistry,
607 Charles E. Young Drive East,
Los Angeles,  CA 90095-1569
USA

E-mail :   scerri(at)chem.ucla.edu
tel:  310 206 7443
fax:  310 206 2061
Web Page:    http://www.chem.ucla.edu/dept/Faculty/scerri/index.html

Editor  of  Foundations of Chemistry
http://www.kluweronline.com/issn/1386-4238

Also see International Society for the Philosophy of Chemistry
http://www.georgetown.edu/earleyj/ISPC.html