Nuclear octupole correlations and the enhancement of atomic time-reversal violation - art. no. 035502

We examine the time-reversal-violating nuclear "Schiff moment" that induces electric dipole moments in atoms. After presenting a self-contained deriva tion of the form of the Schiff operator, we show that the distribution of S chiff strength, an important ingredient in the ground-state Schiff moment, is very different from the electric-dipole-strength distribution, with the Schiff moment receiving no strength from the giant dipole resonance in the Goldhaber-Teller model. We then present shell-model calculations in light n uclei that confirm the negligible role of the dipole resonance and show the Schiff strength to be strongly correlated with low-lying octupole strength . Next, we turn to heavy nuclei, examining recent arguments for the strong enhancement of Schiff moments in octupole-deformed nuclei over that of Hg-1 99, for example. We concur that there is a significant enhancement while po inting to effects neglected in previous work (both in the octupole-deformed nuclides and Hg-199) that may reduce it somewhat, and emphasizing the need for microscopic calculations to resolve the issue. Finally, we show that s tatic octupole deformation is not essential for the development of collecti ve Schiff moments; nuclei with strong octupole vibrations have them as well , and some could be exploited by experiment.