Ernst angle
In nuclear magnetic resonance spectroscopy and magnetic resonance imaging, the Ernst angle is the flip angle that maximizes the steady-state signal for a spin with a spin–lattice relaxation time T 1 {\displaystyle T_{1}} using a flip repetition time T R {\displaystyle T_{R}} , assuming transverse magnetization is eliminated between flips. The Ernst angle θ {\displaystyle \theta } is calculated using the following relationship, derived by Richard R. Ernst, who won the 1991 Nobel Prize in Chemistry: θ = arccos ( e − T R / T 1 ) {\displaystyle \theta =\arccos(e^{-T_{R}/T_{1}})} The derivation of the Ernst angle equation explicitly assumes that all transverse magnetization is completely eliminated between repetition times.