Authors Clarify Degeneracy Issue

October 2003, page 17

On the first page of our article "The Search for a Permanent Electric Dipole Moment" (Physics Today, June 2003, page 33), we wrote that polar molecules can and do have degenerate pairs of states in which the electric dipole is aligned either parallel or antiparallel to the spin. The unintentional implication is that the degeneracy is exact. In fact, although there are often nearly degenerate pairs of such states, the spin-rotation interaction within the molecule does break that degeneracy. See W. Klemperer, K. K. Lehmann, J. K. G. Watson, and S. C. Wofsy in J. Phys. Chem. 97, 2413 (1993), for a clear discussion of this point. We thank those authors for pointing out our article's lack of clarity.

Norval Fortson

(fortson@phys.washington.edu)

University of Washington-Seattle

Patrick Sandars

University of Oxford

Oxford, England

Stephen Barr

University of Delaware

Newark