The study of pulse frequency offset in surface nuclear magnetic resonance

摘要

An ac pulse at the Larmor frequency can be used to induce subsurface while we apply surface nuclear magnetic resonance method to detect groundwater, the received signal and transmitting signal should have same frequency. However, the received signal is not similar with the Larmor frequency in practice, it is so called pulse frequency offset, and thus the quality of measurement is influenced with the offset. In this paper, the causes of the offset will be discussed; the formula of free induction decay signal of surface nuclear magnetic resonance method is derived; depends on these work, the effect of offset work on surface nuclear magnetic resonance signal is also analyzed. At last, softie significative conclusions are obtained by the analysis of a real-world example.