Experimental Detection of the Magnetic Resonance signal requires

Experimental Detection of the Magnetic Resonance signal requires setting up a non-equilibrium state What is thermal equilibrium available to start with? The spin system, the ensemble, has a time independent Net Magnetization along the z-direction (the direction of the magnetic field) Non-equilibrium Z Y Magnetic field X Tilt the magnetization away from the z-direction Detect the xy component

CW RF Oscillator mw power RF Crystal Detector CWPulsed Mode of detection Detection Pulsed RF Transmitter Signal generation Probe with sample coil and sample in Magnetic Field Display/Record High gain RF receiver/detector Signal receiving and detection Time domain signal to computer for FFT Display monitor/Plotter

Oscillation Level reduced when there is ESR absorption Oscillation Level at fixed frequency ‘ν’ When No ESR Detected DC Level No ESR 2 Oscillator Φ Oscillation Level Detector 1 Reduced DC On ESR Absorption Shifter hν=gβH No oscillations 0 The role of a phase Φ shifter in the diagram would be explained in the succeeding slides If the Current is increased from 0 to beyond resonance field, then, the field [ Ht ] increases with time and causes resonance at resonance field value Ht hν=gβH 2 Current Source CLICK to transit to next slide 1

Z - Magnetization along the Field XY - Magnetization induces RF signal in the receiver coil Z Defocusing and signal decay Y X Output from receiver coil - FID RF Pulse : π/2 pulse to flips the magnetization into xy plane CW Oscillator GATE Receiverdetector RF Pulse DC Pulse generator Probe In Magnet Display Monitor Recorder