Click Net Up spin resultant Down spin resultant

Click…. . Net Up spin resultant & Down spin resultant +2 z +8 Vector length representation of strength Vector length corresponds to the Intensity of Net Magnetization Thickness indicates strength 0 y x π/2 pulse -2 -24 Redrawn with vector origin set convenient to visualize addition ‘π/2’ x-pulse, causes the rotation of the magnetization (from z-axis) in the counter clock wise sense by 90º. Magnetization, immediately after the pulse is along the –y axis. Click…. . Transit to next slide 1

Non interacting AX spin system JAX = 0 +7 A spin system +2 +8 Transitions +3 -1 X spin system + +1 z - 0 y -2 + -9 x π/2 pulse Transitions -24 +6 +1 -10 -1 -1 -17 + -3 2

‘A’ system (for non interacting case) magnetization immediately following the 90º, evolves in the XY plane (at precession frequency) Energy level scheme for the case of J=0; AX system Interacting AB spin system ; JAB ≠ 0 +7 +3 -1 + +1 If the JAB = 0. 04 Hz, then the split magnetizations would precess with different frequencies, 0. 182 Hz (lower) and 0. 222 Hz. (higher) 0. 05 Hz - 0. 2 Hz -9 - -1 -17 + -3 Unsplit A and B The two transitions which were of equal energy, have become unequal with one having higher energy and the other having lower energy when J is nonzero; this true for both A and B spin systems This results in the splitting of the lines in spectrum. The AB spectrum would have four lines, as two doublets 3

Apply magnetic field Immediately after the magnetic field is applied When a π/2 pulse is applied After the lapse of T 1 relaxation time & under thermal equilibrium The [I 1+ I 2 - + I 1 - I 2+] combination connects Δm =0 transitions hence creates coherences of zero order (undetectable) during the pulse. If the product operator consists of [I 1+ I 2+] combinations, typically this product would create Spin 1 system coherence (detectable) of order 1. [I 1+ I 2+] combinations cause under pulsed excitations coherences (undetectable) of order 2, and under CW irradiations can cause Δm =2 transitions depending on whether allowed or not. 4

Z- Magnetization brought to xy plane ± 1/2 Random phase for xy components Above motion of xy components at time scales small compared to transverse relaxation time Thermal equilibrium “time scales much greater than T 2” "Wondershare PPT to WMV" conversion Softwatre 5