Authors Clarify Degeneracy Issue

OCT 01, 2003

Norval Fortson

Patrick Sandars

Stephen Barr

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.

More about the Authors

Norval Fortson. 1(fortson@phys.washington.edu) University of Washington–Seattle, US .

Patrick Sandars. 2 University of Oxford, Oxford, England .

Stephen Barr. 3 University of Delaware, Newark, US .