OscillatorOscillation

Level Detector

Current Source

Oscillation Level at fixed frequency ‘ν’ When No ESR

Oscillation Level reduced when there is ESR absorption

Detected DC Level No ESR

Reduced DC On ESR Absorption

hν=gβH No oscillations 0

1

2

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

2

1

hν=gβH

The role of a phase Φ shifter in the diagram would be explained in the succeeding slides

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Φ Shifter

Ht

Z - Magnetization along the Field

RF Pulse : π/2 pulse to flips the magnetization into xy plane

Defocusing and signal decay

Output from receiver coil - FID

XY - Magnetization inducesRF signal in the receiver coil

CW Oscillator

GATE

DC Pulse generator

Probe In Magnet

RF Pulse

Receiver- detector

Display Monitor Recorder

-1.00

-0.50

0.00

0.50

1.00

1.50

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50

Time

am

plitu

de

arb

un

its

FID withoffset

FID onresonance

Z

X

Y

-0.1

-0.05

0

0.05

0.1

0.15

0.2

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 2 4 6 8 10 12 14 16

OUTPUT from the FFT Program: Time domain FID and the Frequency domain two line NMR spectrum

Real

imaginary

Field= H

H/2

H/4

H/6.6

Spectrometer operating frequency decreases

Distance of separation between the multiplets varies with the field

Separation within the multiplets remain unchanged with the field