Nuclear quadrupole resonance spectroscopy
The nuclear quadrupole resonance spectroscopy (or - tomography , in British Nuclear quadrupole resonance , abbreviated NQR called) is the one from magnetic resonance imaging derived (NMR) (depending on the process, imaging) examination technique in materials science, safety technology and medicine. It is used to represent atoms whose nuclei have a quadrupole moment (e.g. nitrogen -14, chlorine -35 or copper -63). In contrast to NMR, the NQR does not require a static external magnetic field , which is why this method sometimes zero-field NMR (zero-field NMR) is called. One problem with nuclear quadrupole resonance spectroscopy is that many of the transit frequencies studied are highly temperature dependent, making nuclear quadrupole resonance spectroscopy difficult to use outside of materials science . Another is the low signal strengths of the resonance radio signals.
There are some research groups around the world who are currently working on using nuclear quadrupole resonance spectroscopy to detect explosives (mostly nitrogen compounds) or drugs. The first devices for detecting landmines and bombs in luggage have already been tested, with the first such detectors being used at the 1996 Olympic Games in Atlanta. Another application is the measurement of the composition of water , oil and gas in oil wells in real-time to the delivery process to be able to control better. The system itself consists of a radio wave transmitter , a coil ( quadrupole magnet ) for generating the magnetic excitation field and a radio wave receiver that evaluates the NQR responses of the atoms. In the case of double or multiple resonance methods, the ratios of the resonance signals sent by different atoms are also considered in order to achieve good sensitivity even with compounds that deliver very low resonance signals ( e.g. TNT ).