Quadrupole relaxation enhancement-application to molecular crystals

► In this study we discus quadrupolar relaxation enhancement (QRE) effects. ► A general theory of the enhanced dipolar spin relaxation is presented. ► Arbitrary motional conditions and interaction strengths are considered. ► QRE theory is applied to the crystal [C3N2H5]6[Bi4Br18]. ► Difference between polarization transfer and relaxation enhancement is discussed.