Earth’s Field NMR: first draft

Abstract

We examined the relationship between magnetization, polarizing field time, magnetic field and precession frequency using a 125 mL sample of water and the TeachSpin Earth’s Field NMR instrument. Through varying these different parameters, we could determine the Larmor precession frequency of protons within Earth’s field, spin-lattice relaxation time, and the gyromagnetic ratio for protons. We found the Larmor precession frequency to be $$1852\pm18~Hz$$ corresponding to a local magnetic field of $$43.3\pm 0.3 \mu T$$ due to Earth’s magnetic field, the spin-lattice relaxation time to be $$2.15\pm0.05~s$$, and the gyromagnetic ratio to be $$(2.65\pm0.04) \cdot 10^8~\frac{1}{s\cdot T}$$, agreeing with the known value of $$2.68\cdot 10^8~\frac{1}{s\cdot T}$$.

Aims

This experiment was designed to test the relationship between magnetization of protons, dependence on the polarizing field, and Larmor frequency by making a direct measurement of the gyromagnetic ratio and the field dependence of the precession frequency of protons in weak fields.