Quadrupolar Deformations of Atomic Bubbles in Solid4He

Abstract
We have studied the magnetic properties of Cs atoms trapped in cubic and hexagonal solid 4He matrices. Observations in the cubic phase support the assumption of a highly symmetrical trapping site (spherical bubble), while zero-field magnetic resonance spectra and magnetic dipole-forbidden transitions observed in the hexagonal phase are interpreted in terms of a quadrupolar distortion of the atomic bubbles. From the perturbed hyperfine interaction in the hexagonal phase we infer a bubble deformation of 6%7%.