1. Nuclear Magnetic Resonance
ANIMATED ILLUSTRATIONS
MS Powerpoint Presentation Files
Uses Animation Schemes as available in MS XP or MS 2003 versions
A class room educational material
File-1 FT NMR-1D
12/5/ :37:06 PM
Dr.Aravamudhan

2. tm t1 t2 Acquisition for duration t2 ω1 ω2
Evolution period t1
Mixing period tm (Fixed duration) t1 tm
Acquisition for duration t2 t2
Depends on the choice of the type of 2D experiment ω2 ω1
2D Spectrum Contour plot
2D NMR pulse sequence structure

3. There has been no MULTIPLE PULSE SEQUENCE considered in this illustration. This only to illustrate the spectrometer settings required while setting up multiple pulse experiments. Two dimensional spectra contain rich information if the spin system is allowed to evolve under multiple pulse perturbations before acquisition of FID.

4. A typical two pulse sequence for 2D experiment
mixing
(π/2)y
Prepararion
Acquisition t 2
Evolution t1 M0 R
This sketch above and the 2D consequent would be elaborated at a later stage to follow. y x
A description of multiple pulse 2D experiment: A generalized depiction below………..
Preparation
Evolution t1
Mixing t ime τ
Detection t2
t1 is varied from scan to scan
τ is fixed
acquisition

5. P2y P1x P2y P2y τ is fixed t1 is varied from scan to scan Z-axis
Y-axis
Spin system evolves freely;
Magnetization vector precesses in XY plane
P1x
X-axis
For the ‘Y’ axis π/2 pulse the component along –X axis gets to Z direction
Typical spin system manipulation by multiple pulse sequence
for two dimensional experiments
Precession by about 45°: can be resolved into components along X and Y axes
P2y
If the Spin system continues to evolve freely without any intervening pulses,
Magnetization vector precesses in XY plane by angle π/2 so that the entire magnetization would be along –X axis.
Thus the magnetization vector is sent to –Z direction by this pulse along Y-axis
P2y
Preparation
Evolution t1
Mixing t ime τ
Detection t2
t1 is varied from scan to scan
τ is fixed
acquisition
12/28/2010 8:47:59 AM
Dr.Aravamudhan

6. Experiment with increasing t1 , the evolution time :increment 10μs
How will the FT for each of this FID would look?
Scan 1 3 2 3 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 8 6 4 2 1 2 4 5 6 5 2 5 4 1 4 3 3 4 5 5
DW =5μs
Scan 2 3 3 2 2 4 3 2 3 2 2 1 2 4 5 6 5 3 2 4 4 3 2 2 1 4 3 2 3 3 4 4 5 5 5 4 3
Scan 3 3 3 2 2 2 1 2 4 5 6 5 4 3 2 3 4 5 5 5 4 3 2 3 3 4 4 4 3 3 2 2 2 3 1
Scan 4 3 2 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 4 5 6 5 4 3 2 3 4 5 5 5 4 3 1
Scan 5 3 3 2 2 2 3 3 3 2 2 2 6 5 1 4 3 2 3 5 3 2 3 4 4 4 4 5 5 4 3
Scan 17 2 2 1
12/28/2010 8:47:59 AM
Dr.Aravamudhan

7. Note the variation and intensities and the initial phases of the FID
FT Spectrum
FID
0 μs
Scan 1
Scan 2
10 μs
15 μs
Scan 3
20 μs
Scan 4
Note the variation and intensities and the initial phases of the FID
12/28/2010 8:47:59 AM
Dr.Aravamudhan

8. Acquisition time Detection time t25 3 2 3 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 8 1 6 4 2 1 2 4 5 6 4 3 2 3 4 5 5 5 4 3 3 2 2
10 μs 4 3 2 3 2 2 1 2 4 5 6 5 3 2 2 1 4 3 2 3 4 5 5 5 4 3 2 3 3 4 4 4
15 μs 1 2 4 5 6 5 4 3 2 3 5 5 4 3 2 3 3 4 4 4 3 3 2 2 2 3 3 3 2 2 2 1 4 5 3 3 2 2 2 3 3 3 2 2 2 4 5 6 5 4 3 2 3 4 5 5 5 4 3 2 3 3 4 4 4 1
20 μs 3 3 2 2 2 6 5 3 2 3 4 3 2 3 2 2 1 3 4 5 5 4 3 2 5 3 3 4 4 4
25 μs
170 μs 2 2 1
Acquisition time Detection time t2
There are 2 time axes and FT is carried out along both time axes
The signal amplitudes as a function of time for the FID are stored in the memory for each delay time defining the evolution time t1
12/28/2010 8:47:59 AM
Dr.Aravamudhan

9. t1
Amplitude of the signal as a function of t2 for the various evolution times t1
Matrix S (t1, t2) t2
FT along t2 axis
S (t1, t2)
S (t1, ν2)
FT along t2 axis
FT along t1 axis t1
S (ν 1, ν2)
FT along t1
axis
ν 1 ν2 ν2
12/28/2010 8:47:59 AM
Dr.Aravamudhan

10. Magnetization vector precession y
Pulse
Pulse
Reference
Acquisition
Real part spectrum x y x
cos z
The reference phases were exactly along the Axis, thus phase difference between signal and reference was 0,π/2,π or 3π/2 y y
sin
Magnetization vector precession
Animated illustration of the variety of the FID waveforms. All descriptions are in rotating reference frames
If the phase difference was not integer multiple of π/2, then ?
Next sllde… y -x
-cos y -y
-sin
12/28/2010
Dr.S.Aravamudhan

11. t0 t1 ω1 t2 t3 t4 ω2 ω2 M0 y x (π/2)x (π/2)y My Evolution t1 (π/2)y R
mixing
(π/2)y
Prepararion
Acquisition t 2 My
Evolution t1
(π/2)y M0 R Mc Mz y
Only cosine component is acquired x t0
Red dots constitute time domain points along t1 t1 ω1 t2 t3 t4 ω2 ω2
12/28/2010
Dr.S.Aravamudhan