Manifestation of Berry’s Phase in Nuclear Quadrupole Resonance Spectra of Rotating Powder Samples

<jats:p>The effect of Berry’s phase on the nuclear quadrupole resonance (NQR) spectra of rotating powder samples is studied experimentally, and its application for the determination of the electric field gradient asymmetry η is demonstrated. The NQR frequency splittings, which are observed for the spin 3/2 nucleus of <jats:sup>35</jats:sup>Cl in powder samples of p-dichlorobenzene (C<jats:sub>6</jats:sub>H<jats:sub>4</jats:sub>Cl<jats:sub>2</jats:sub>) and cyanuric chloride (C<jats:sub>3</jats:sub>N<jats:sub>3</jats:sub>Cl<jats:sub>3</jats:sub>), are interpreted as a manifestation of Berry’s phase, associated with the adiabatically changing Hamiltonian due to sample rotation. The accumulation of Berry’s phase during the rotation process is responsible for the observed dependence of the NQR line shape on the rotation frequency and the asymmetry parameter. The proposed method for the determination of η involves the analysis of the NQR powder patterns of the rotating samples.</jats:p>