Long range detection of explosives or contraband using nuclear quadrupole resonance

Apparatus for long distance detection of a substance utilizing nuclear quadrupole resonance, comprising:

• at least one antenna for projecting two overlapping high frequency beams towards a given area;
• a pair of transmitters, one of said transmitters operating at a first frequency and the second of said transmitters operating at a different offset frequency, the offset being that associated with the resonant frequency of the substance to be detected, said transmitters being coupled to said at least one antenna;
• a receive antenna tuned to the resonant frequency of the substance;
• a cross product modulation detector coupled to said receive antenna for detecting the cross product modulation product corresponding to the resonant frequency of the corresponding substance;
• and,
• an explosive/contraband detector coupled to said cross product modulation detector for detecting a stimulated emission response of any of said substance in the overlapped beams, said explosive/contraband detector coupled to a signature library such that correlation between the stimulated response signature and at least one signature in the signature library is detected, such that if said substance exists in said crossed beams, the existence thereof will be ascertained.