Calculation of the energy transferred by radiation damping from nuclear spin system to receiver coil in NMR

In nuclear magnetic resonance (NMR) experiments the free induction decay (FID) current is induced by the precession of the excited magnetization, and the FID signal carries energy. This energy must come from the spin system, but has never been investigated quantitatively. This letter finds a way to calculate the energy trans formed from the magnetic potential energy in the spin system to the electric kinetic energy associated with the FID current by revisiting the radiation-damping-modified Bloch equations. The result shows that under strong radiation damping conditions, almost all of the energy stored in the excited spin system is transferred to FID with negligible energy loss.