Robust detection of nuclear quadrupole resonance signals in a non-shielded environment

Nuclear quadrupole resonance (NQR) is a non-invasive radio-frequency technique allowing for a practically unique fingerprint for molecules containing quadrupolar nuclei, making the technique very promising for detection purposes. If properly excited, these nuclei will emit electromagnetic radiation, the frequency of which is governed mainly by where in the molecule the nuclei are positioned. However, the resulting NQR signals are inherently weak and are prone to strong interference signals from the measurement environment, making detection challenging. In this paper, we develop a robust and reliable detection algorithm that generalize earlier techniques and incorporates both efficient interference cancellation and the ability to handle multiple polymorphs in the sought substance. The usefulness of the algorithm is motivated by comparisons using realistic simulations.