Re: neutron polarization

[Paul Zitzewitz <pzitzewi@SB-F1.UMD.UMICH.EDU>]

Neutrons do have a charge distribution:  the sign of the charge
density depends on the distance from the center.  They do not have a
permanent electric dipole moment (edm)  (this has been measured many
times to very high precision).  Basically, if they had a dipole
moment, then they could be accelerated by an electric field gradient,
or they would have a preferred axis in a uniform electric field.  I'm
pretty sure that the neutron edm is measured this way.

Any temporary dipole moment (i.e., polarization) would probably
require very high electric fields, comparable to those within nuclei.
An experiment with free neutrons would probably see an effect that
was proportional to the square of the applied electric field but
independent of its direction.

I would guess that the effects of polarization within nuclei would be
very hard to separate from effects due to the strong nuclear force.

I was a student of Norman Ramsey who did many of the neutron edm
measurements. I've asked him the question.  I know that he is
retired, but still very active.  I hope to hear from him.


> Please pardon the repetition if you've seen this message before --
> there was no response, and it seemed as though our server or the
> Listserv was acting funny at the time I first sent it.
> We are discussing the electrostatic polarization of neutral objects,
> both conductors and insulators,  and a student has asked, if
> molecules and atoms can be polarized by an external charge,  then how
> about neutrons?

Paul Zitzewitz, Professor of Physics
Department of Natural Sciences
University of Michigan-Dearborn
4901 Evergreen Rd
Dearborn, MI 48128
(313) 593-5158 FAX (313) 593-4937