NQR detection using a meanderline surface coil

14N pure NQR detection in a thin-layer sample using a meanderline, or zig-zag, surface coil is reported. The RF magnetic field of the meanderline drops off approximately as exp−πhb), where b is the conductor spacing and h is the distance from the plane of the coil, and therefore is ideally suited for NQR detection in thin, planar samples. A meanderline with 11 conducting strips of 4 cm spacing was used to observe the 14N ν-resonance line in sodium nitrite at sample distances up to 1.6 cm, where the RF field has dropped to less than 1e. The meanderline results are compared with those obtained using a solenoid of comparable dimensions. It is also shown that the sensitivity of NQR detection using surface coils is greatly enhanced by using fast-pulsing techniques such as the strong off resonance comb, which can produce an order-of-magnitude or better improvement in the signal-to-noise ratio over more conventional (T1-limited) techniques.