Nuclear quadrupole resonance
Nuclear quadrupole resonance spectroscopy or NQR is a chemical analysis technique related to nuclear magnetic resonance (NMR). Unlike NMR, NQR transitions of nuclei can be detected in the absence of a magnetic field, and for this reason NQR spectroscopy is referred to as "zero Field NMR".
Source: Wikipedia — Nuclear quadrupole resonance (CC BY-SA 4.0)