Bloch equations, Larmor precession & Rabi oscillations
ESR resonance condition: ω₀ = γB₀ where γ = 1.761×10¹¹ rad/(s·T) for electrons. The Bloch equations describe magnetization: dM/dt = γM×B − relaxation. T₁ (longitudinal) restores Mz; T₂ (transverse) dephases Mxy. On resonance, the B₁ RF field drives Rabi oscillations with frequency Ω_R = γB₁/2, flipping the spin between |↑⟩ and |↓⟩.