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-8 FT NMR-I
12/28/2010 8:47:59 AM
Dr.Aravamudhan

2. t ω = 2 π ν Fourier Transform The time domain signal forms ω ω ω ω ω ω
Real Part
Imaginary part ω t ω
Cosine form at angular frequency ω
Corresponding Exponentially Decaying function ω ω
The sine function ω ω
ω = 2 π ν
ν is in cycles per second
ω is in radians per second
12/28/2010 8:47:59 AM
Dr.Aravamudhan

3. t AUDIO SIGNAL (FID) FROM PSD IS ANALOGUE SIGNAL WHICH IS DIGITIZED +48 8 +4 16 6 24 +2 29 33 4 2 31 35 -2 27 20 -3 1 12 4 t 4 8 12 16 20 24 27 29 31 33 35
Each one of the time interval of duration specified within the line with double ended arrow is the digitizer time [per[point, i.e., the Dwell Time DW. 35 values are recorded in 35 DW
For DW=5 μs with 36 data points (0,1…35)
Acquisition time = 36x5= 180 μs
12/28/2010 8:47:59 AM
Dr.Aravamudhan

4. 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

5. 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

6. 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

7. 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

8. 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