I have been following the MDN exchanges about
polarisabilities of H2 and D2 with interest but was
too busy last week on other fronts to contribute my
bit. In the meantime, most of the issues raised seem
to have been sorted out. The original enquiry
concerns a classic question, addressed reasonably
conclusively by experimentalists and theoreticians
alike at least 30 years ago.

Martin Bogaard and I reviewed the subject in an
article entitled "Electric dipole polarisabilities of
atoms and molecules", published as Chapter 5
in MTP Review of Molecular Structure and
Properties, Series II (ed. A.D.Buckingham,
Butterworth, 1975), vol. 2, pp. 149 - 194.
Relevant bits of what we had to say then are
attached.

There are good-quality values for the static
(dc-field) polarisabilities of H2 and D2 from
dielectric polarisation and molecular beam
electric resonance measurements, yielding
isotropic and anisotropic parts, respectively.
The H2:D2 ratio for the former is 1.012 and
1.034 for the latter. Likewise, H2:D2 ratios
for optical polarisabilities at 632.8 nm are
1.012 for the isotropic part (from refractive
index measurements) and 1.054 for the
anisotropic part (from Rayleigh scattering
depolarisation-ratio measurements).

The source of these significant polarisability
differences between H2 and D2 are what has
been referred to by other MDN correspondents
as "zero-point effects" -- see the attached
extract from our review for more on this subject.
The key parameters are the first and second
derivatives of the polarisability tensor with
respect to the internuclear distance. Two more
recent (but still ancient!) important papers in that
regard are:
   Hamaguchi, H., Suzuki, I. and Buckingham,
      A. D. (1981). Molec. Phys., 43, 963
   Hamaguchi, H., Buckingham, A. D. and
      Jones, W. J. (1981). Molec. Phys., 43, 1311

It is nice to know that this is an area where careful
experiment and theory are in agreement!

Brian Orr


Date sent: Thu, 13 Jun 2002 13:29:28 -0400
Send reply to: Daniel Willey <[log in to unmask]>
From: Daniel Willey <[log in to unmask]>
Subject: Polarizability of D2
To: MOLECULAR-DYNAMICS-
[log in to unmask]

> Does any one happen to know the polarizability of molecular
> deuterium, D2? And, if you don't know it, is there any reason to
> expect it to be very different form the polarizability of H2?
>
> Thanks,
>
> Dan
> --
> Dan Willey
> Chairman
> Department of Physics
> Allegheny College
> 520 N. Main St.
> Meadville, PA 16335
> 814-332-5368 or 332-5364
> [log in to unmask]



************************************************
Brian J. Orr
Professor of Chemistry and Head of Department,
Department of Chemistry,
Division of Environmental & Life Sciences
Macquarie University, Sydney NSW 2109 AUSTRALIA

Also:
Deputy Director, Centre for Lasers & Applications

PHONE:
+61-2-9850-8289 (regular office); -8311 (laser lab);
+61-2-9850-8275 (Dept. office); +61-2-9416-7214 (home)

FAX:
+61-2-9850-8313 (general); +61-2-9850-9396 (secure)

E-MAIL:
[log in to unmask] (general);
[log in to unmask] (Head of Department)

Web home page:
http://www.chem.mq.edu.au/academics/orr.htm

This message is intended for the addressee named
and may contain confidential information. If you
are not the intended recipient, please delete it
and notify the sender. Views expressed in this
message are those of the individual sender, and
are not necessarily the views of the University.
************************************************