Nuclear Schiff moment and soft vibrational modes

Abstract

The atomic electric dipole moment (EDM) currently searched by a number of experimental groups requires that both parity and time-reversal invariance be violated. According to current theoretical understanding, the EDM is induced by the nuclear Schiff moment. The enhancement of the Schiff moment by the combination of static quadrupole and octupole deformation was predicted earlier.Here we study a further idea of the possible enhancement in the absence of static deformation but in a nuclear system with soft collective vibrations of two types. Both analytical approximation and numerical solution of the simplified problem confirm the presence of the enhancement. We discuss related aspects of nuclear structure which should be studied beyond mean-field and random phase approximations.

The observation of vibrating pear-shapes in radon nuclei

“…4), and will be in general much larger than that the value (≈ 50 keV) observed for parity doublets in radium isotopes1. Realistic estimates of Schiff moments for octupole-vibrational systems have yet to be made [32,33]. Nevertheless, it can be concluded that, if measurable CP-violating effects occur in nuclei, the enhancement of nuclear Schiff moments arising from octupole effects in odd-A radon nuclei is likely to be much smaller than for heavier octupole-deformed systems.…”

Nuclear structure features of Gamow-Teller excitations

“…Later this effect was qualitatively observed in the data for other isotope chains [13]. The same idea was useful in the theoretical search [14] for the enhancement of the nuclear Schiff moment, important in the problem of the electric dipole moment, due to the combined action, and therefore correlation, of soft quadrupole and octupole modes [15].…”

Collective dipole excitations in sodium clusters

“…Instead of the usual transition dipole operator, we make use of a modified operator which is similar to the so-called Schiff moment from nuclear physics [36].…”