Subject: RE: orbitals and reality

From: "Shobe, David" <dshobe)at(sud-chemieinc.com>
Date: Wed, 19 Jan 2005 10:25:26 -0500

Dear Demetrios, and CCL readers:
 
I wouldn't read anything into Sengen's use of this forum (CCL) rather than a letter to the editor, to discuss his disagreement with the conclusions of the Scerri "orbitals" paper.  He may have intended this to be a philosophical discussion among friends, whereas a letter to the editor might be considered a direct confrontation.  And not everyone likes to make direct confrontations.  
 
On the other hand [Dear Sengen]: Writing a "Comment on..." letter to the Journal of Chemical Education may be an opportunity to start a debate on "orbitals and reality--and what should we teach our students?" among teachers of chemistry.  Not to mention a way to lengthen your publications list. ;-)  
 
--David Shobe, Ph.D., M.L.S. 
Süd-Chemie, Inc. 
phone (502) 634-7409 
fax (502) 634-7724 

Don't bother flaming me: I'm behind a firewall. 

-----Original Message-----
From: Computational Chemistry List [mailto:chemistry-request)at(ccl.net]On Behalf Of Demetrios Xenides
Sent: Wednesday, January 19, 2005 4:53 AM
To: chemistry)at(ccl.net
Subject: CCL:orbitals and reality

Wouldn't also be a good idea to see something published (comment or another paper) by the guy (Sengen Sun) who has started the discussion? If he is so very much determined that the authors have not made an important step forward on the (possible) mapping of MOs then his comments would be highly appreciated by the "misleaded" scientific community.

Cheers
Demetrios

p.s. respect to the people who not only performed a study but they published it as well.

From: Computational Chemistry List on behalf of Sengen Sun

Sent: Mon 1/17/2005 4:46 PM

To:  chemistry)at(ccl.net

Subject: CCL:orbitals and reality 

I have been asked to make a summary on this year

discussion on this subject. I received responces from

10 this year. 3 of them are neutral, 5 agree, and 2

disagree. I am specially interested in the

disagreements and therefore post them here. I would

think the first one might be meaningful. And we will

have to see.

I would be much happier if Mikael P Johansson and any

one else could also critisize my earlier postings on

the List as well :-). Here are two examples:

http://www.ccl.net/cgi-bin/ccl/message.cgi?2003+07+28+001;

http://www.ccl.net/cgi-bin/ccl/message.cgi?2003+06+02+016;

The second disagreement is not specific enough. But I

will address it later after Mikael P Johansson's next

message or posting.

Cheers!

Sengen

--- Mikael P Johansson   <mailto:mikael.johansson)at(helsinki.fi> <mikael.johansson)at(helsinki.fi>

wrote:

Well, if it helps, I disagree with you :-) I will

write up a "pro-orbital"

mail for CCL as soon as my work load permits.

Happy New Year,

    Mikael J.

     http://www.helsinki.fi/~mpjohans/

--- @yahoo.com> wrote:

Hello Dr. Sun,

It's interesting to see your posts about that paper.

Since I am very busy I have not read the details of

the paper. However it

looks like what they did in the paper is very

important and meaningful.

I think they derived some information about the

orbital from experiments

and data analysis, similar to the X-ray data

analysis in some sense. Also

they mentioned that the phase component of the wave

function is arbitary.

Very likely they derived the real part or the

imaginative part, or at

least some of either.  So it's still very meaningful

  

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---

From: "Phil Hultin" <hultin..at..cc.umanitoba.ca>
Date: Thu, 20 Jan 2005 08:58:39 -0600

This is a copy of a note I sent to Sengen Sun.  I am posting it now because
there does seem to have been some interest in the issue he raised on CCL -
at the time there had been no response.  Dr. Sun has promised to respond to
my comments in the future.
====================================
Dr. Sun:

I noted your request for further response to the "orbital debate" that has
arisen from the Nature paper by Villeneuve et al.

The orbital model is undeniably a key part of modern electronic structure
theory, and it is therefore understandable that experimentalists would seek
physical confirmation (if not proof) of its validity.  On the other hand, it
is equally true that theoreticians have always maintained that orbitals are
"merely" mathematical constructs, that any arbitrary set of orbitals does
not represent a unique solution to the Schroedinger equation, and that
orbitals are therefore non-physical and non-observable.

So, to get to the argument over Villeneuve et al: Having read the paper I
must confess that I do not fully understand the experiment that they did.
They assert that the overtone spectra that they acquire encode symmetry
information about the electronic state (which they call an orbital) from
which the electron is ejected and to which it returns.  Since they cite
literature support for this assertion I am prepared to accept it for the
sake of argument until someone provides a persuasive counter argument.

So, the question is, what did they actually observe and how should it be
interpreted?  I suggest that denying their experiment on theoretical grounds
is scientifically inappropriate.  Observation must have priority over
theory, or we are talking about religion instead of science.  This doesn't
mean that they actually observed an orbital - but rather, if you are going
to criticise their interpretation of the data you should present an
alternative explanation of the origin of their spectra that is consistent
with your view of electronic theory as well as with their observations.

While the fact that orbitals are "only a model" means we must not assume
that they are "real", I suggest that it is inappropriate to take it as
axiomatic that the orbital model cannot embody at least some aspect of
physical "reality".  It is entirely possible that electronic structure
behaves under certain specific probes as if orbitals were real, that is,
that our artifical model fortuitously captures an observable aspect of
electrons.

I don't want to argue that Villeneuve et al are correct.  But please, if you
really want to conduct a scientific debate, address their experimental
observations directly and don't simply say that "because they are
inconsistent with theory they must be false". 

Dr. Philip G. Hultin
Associate Professor of Chemistry,
University of Manitoba
Winnipeg, MB
R3T 2N2
hultin..at..cc.umanitoba.ca
http://umanitoba.ca/chemistry/people/hultin

---

From: "Shobe, David" <dshobe{at}sud-chemieinc.com>
Date: Thu, 20 Jan 2005 15:23:45 -0500

Since I've stepped into this discussion, perhaps I ought to at least look at the paper that started this.  :-)  Does anyone have a usable citation?  I'm seeing different authors and different journals mentioned...which probably means there is more than one article.  The article I am interested in is the one which describes how the "orbitals" were observed "experimentally".

S|d-Chemie, Inc.
phone (502) 634-7409
fax (502) 634-7724

---

From: "Shobe, David" <dshobe|at|sud-chemieinc.com>
Date: Thu, 20 Jan 2005 15:17:14 -0500

Here's an interesting and related question: 

Are symmetry groups (point and space groups) real?  These are also "mathematical constructs".

(As for myself, I tend to "reify" mathematical objects, but relegate them to a separate "math world.")