Subject: Re: CCL:Seeing molecular orbitals?

From: "Henry Pang" <[email-masked]>
Date: Fri, 21 Jul 2000 00:05:57 GMT

Hi Jens (Denmark)

You said <But strictly speaking, this does not turn MOs into
>observable quantities; MOs have no physical existence>

I am new to computational chemistry. My background is medicine and human 
ecology in Australia. Your post is the first indicator I have seen over a 
wide range of CCL and books which signals caution. I am overwhelmed by the 
volume and intensity of work on the methodology and mensuration of 
molecules, as if that were the end in itself. No where do I see any concern 
for a Philosophy of Computational Chemistry, which addresses just what is 
computational chemistry and what its purpose might be in our Universe. I 
cannot believe the objective is merely to measure everything and simply 
document these data?

Even at my early stage, I am seriously pondering writing material jointly 
with my academic supervisor who is a computational chemist, which sets out 
the link (as I see it) between cosmology, quantum theory, relativity and 
higher dimensions theory on the one hand and computational chemistry on the 
other. I think molecules are the beautiful building blocks of our Universe 
and created for a purpose. I decline the view molecules are just chance 
particles. I suspect from my reading of CCL, my intention may be seen as 
revolutionary if not outrageous and could well cause an uproar?

Best wishes from Australia

Dr Henry Pang
Postgraduate Student, Computational Chemistry
Faculty of Science, Information Technology and Education
Northern Territory University
PO Box U273 NT University 0815 Australia
Mobile 61 419 682121 Fax 61 8 8946 6847 [email-masked]

----------------------------------------------------------------------

>From: "Jens Spanget-Larsen" <[email-masked]>
>To: [email-masked]
>Subject: CCL:Seeing molecular orbitals?
>Date: Thu, 20 Jul 2000 10:43:01 +0100
>
>Dear CCL:
>
>In a recent, most interesting publication ('Seeing molecular orbitals',
>Chem.Phys.Letters 321, 78-82 [2000]) scanning tunneling microscopy is used 
>to
>observe the shapes of single molecular orbitals of the fullerene C60:
>
>   "..the scanning tunneling microscope (STM) is probing a single molecular
>   orbital (MO)."
>
>However, this reminds me of previous statements in the literature some time
>ago, associated with the advent of molecular photoelectron spectroscopy, 
>f.i.
>
>   "Chemists can see the orbital structure of even fairly large molecules 
>and no
>   longer have to rely on the predictions of theoreticians"
>
>   "Photoelectron spectroscopy has demonstrated experimentally to chemists,
>   physicists and other sceptics that molecular orbitals really do exist"
>
>I wonder whether this is acceptable terminology, considering the fact
>that molecular orbitals are model constructs; they are not physical
>observables. By using approximations, such as Koopmans' approximation, many
>experimental observations can be conveniently interpreted in terms of
>theoretical MO data. But strictly speaking, this does not turn MOs into
>observable quantities; MOs have no physical existence.
>
>Any comments?
>
>Yours, Jens >--<
>
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>JENS SPANGET-LARSEN         Phone:  +45 4674 2000  (RUC)
>Department of Chemistry             +45 4674 2710  (direct)
>Roskilde University (RUC)   Fax:    +45 4674 3011
>P.O.Box 260                 E-Mail: [email-masked]
>DK-4000 Roskilde, Denmark   http://www.rub.ruc.dk/dis/chem/psos/
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>
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