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 PULSED FT NMR http://ugc-inno-nehu.com/links_fro m_web.html Video Conversion Using “WONDERSHARE PPT to WMV ” Conversion Software Dr. S. ARAVAMUDHAN Automatic Timing: CLICK on “show” and wait and watch all the 13 slides which automatically transit one slide to the next.
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. PULSED FT NMR. http://ugc-inno-nehu.com/links_from_web.html. Video Conversion Using - PowerPoint PPT Presentation
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1
Nuclear Magnetic ResonanceANIMATED ILLUSTRATIONS
MS Powerpoint Presentation Files
Uses Animation Schemes as available in MS XP or MS
2003 versionsA class room educational material
PULSED FT NMR
http://ugc-inno-nehu.com/links_from_web.html
Video Conversion Using
“WONDERSHARE PPT to WMV” Conversion Software
Dr. S. ARAVAMUDHAN
Automatic Timing: CLICK on “show” and wait and watch all the 13 slides which automatically transit one slide to the next.
A steady Uniform Magnetic Field of 9.34 Tesla is applied (find in Slide #3)
Experimental sample is placed in the magnetic field (as in slide#3)
Magnetization Builds up due to Relaxation process in Time T1 (slide#3 & Slide#10)
A rectangular pulse of 400 MHz RF frequency is applied to bring the magnetization to XY Plane (slide #3, 4, &5 and others)
z
xy
Magnetization decay due to T2 process. Free Induction Decay F.I.D. acquired (as in slides # 5, & 10) FID is digitized (slide#6)
FID Fourier Transformed to obtain Spectrum (slide #6)
Obtaining FT NMRElaboration on the even more basic Single spin Magnetic moment situation in a steady applied Magnetic field and the Consequent Magnetization can be viewed at YOUTUBE.COM
x,y-axes Rotating about Lab Z-axis; frequemcy same as the precession frequency
Z
XY A rotating RF magnetic
field results on application of RF at resonance frequency
X
Y
The rotating magnetic field tilts the magentization away from z-axis by 90º for a π/2 pulse
Viewed from within the rotating frame the RF field appears stationary
Tilted Magnetization in xy plane viewed from Lab Frame. Precessing at resonance frequency.
Magnetization in XY plane appears stationary when viewed in Rotating Frame from within the rotating frame
XY
Induced NMR signal at receiver (RF 300 MHz )
Phase Sensitive detector
Reference in phase at NMR (400MHz) frequency
Output (‘0’ freq)
Reference in phase; offset from NMR frequency (400±0.004 MHz)
Phase Sensitive detector
Output at offset frequency (audio range) ~4KHz
D.C.
A depiction of the Induced RF signal Characteristics would appear………
After the pulse: at t>0
Transverse Relaxation and magnetization decay in XY plane is not depicted.
No more CLICKs. This show has automatic timings
from this stage. Free Induction NMR Signal
NO F.I.D. yet!
Right CLICK mouse
And CLICK on option “PREVIOUS”
OR………….
CLICK toTransit.
Rotating x,y axes :rotation about Lab z-axis
Apply the 90º,
-X pulse now, P-Xπ/2
A BLUE line for z-Axis indicates the view from within the rotating coordinate system.
XY
Rotating system viewed from within that system: STATIONARY
X
Y
Z
X
Y
ZZ
Y
4
For a π/2 pulse the value of ‘ω1 t ‘=90º;
ω1=γH1
The impulse on…
x,y-axes Rotating about Lab Z-axis; frequency same as the precession frequency
Z
XY
X
Y
XY
Rotating system viewed from within that system: STATIONARY
X
Y
Z
A rotating RF magnetic field results on application of RF at resonance frequency
Viewed from within the rotating frame the RF field appears stationary
Z = unit vector along z-axis
Rotation about z-axis= e-iφ Z Represents rotation by angle φ about z-axis; Φ can be replaced by frequency of rotation in radians ‘ω’ multiplied by ‘t’ the time lapsed.
Rotation about z-axis= e-i ω t Z
An equation representing this rotation would be displayed
In terms of Angular momenta, Iz replaces ‘z’; for rotation
about z-axis= e-iφ Iz
Represents rotation by angle φ about z-axis; Φ can be replaced by frequency of rotation in radians ‘ω’ multiplied by ‘t’ the time lapsed.
Rotation about z-axis= e-i ω t Iz
RF source/ transmitterConnected to coil.Linearly oscillating field along the coil axis (X-axis)
The linearly oscillating field can be resolved into two counter rotating components
Only one of the rotating component is effective in causing resonance
2 H1 I-x cos(ωt) = H1 e-iI-xωt H1 e+iI-xωt
http://www.geocities.com/sankarampadi/eulexp.html
A Pulse lasts only for a few μ Secs.
For proton NMR a H1 of ~25Gauss along ‘-x’ , pulse widths are approximately 10-15μs
+
The impulse off…
RF field is along –X in the XY plane, the effect caused would be rotation about X-axis, unlike the precession about z-axis
To repeat the animated RF depictions “right click” and choose option: ‘previous’
Click to end this slide
CLICK ! CLICK !
CLICK !
CLICK !
CLICK !
Repeat pulsing?.....Right Click and choose menu option ‘previous’ and CLICK!
Viewed from within the rotating frame the RF field appears stationary
Tilted Magnetization in xy plane viewed from Lab Frame. Precessing at resonance frequency.
XYAfter the
pulse: at t>0
Rotating x,y axes :rotation about Lab z-axis
A BLUE line for z-Axis indicates the view from within the rotating coordinate system.
Z
Y
Magnetization in XY plane appears stationary when viewed in Rotating Frame from within the rotating frame
X
Y
ZWhen the XY magnetization decays with transverse relaxation time T2,
immediately after the pulse……
When PSD reference is in phase off set from Resonance frequency; NMR signal at receiver (RF 400 MHz )
If No T2……..
Free Induction Decay Signal
No More Clicks ! This show has automatic timings
The F.I.D.
When PSD reference is in phase at Resonance frequency; NMR signal at receiver (RF 400 MHz )
Tilting of magnetizationDescribed in rotating frame: Rotation about the X-axis
I(tp) =e-iI-
xφ Iz e+iI-xφ with φ=90º &
tp is pulse duration
At the end of pulse, time for F.I.D. begins with t=0
tp
t=0
Acquisition time ~5T2
FID
CLICK to Transit
Induced NMR signal at receiver (RF 400 MHz )
6
PULSED NMR Acquire F.I.D.
Free Induction DecayNMR detection soon after a strong pulse: precessing nuclear magnetization induces a signal in coil when it is free of the perturbing EM radiation
F.I.D.DIGITIZE
Analogue to Digital Converter
A.D.C.
Address Contents
1 0000
15
1111
2 0001
14
1110
3 0010
13
1101
4 0011
11
1011
5 0100
8
1000
6 0101
4
0100
7
0110
1
0001
8
0111
0
0000
--------- ---------
Computer memory
Time domain
15
0
11
FFT from FID
Computer input
Frequency Domain Spectrum
Computer outputThis one-
dimensional FT NMR spectrum is the same information as the C.W. NMR spectrum
Acquisition is automatically in the digitized form
Next Slide
7
dimension A(50),B(50),Y(50),X(50) K=32 open (unit=1, file="output") Print 10,K DO 11 N=1,K X(N)=(N-1)*3.5/K X(N)=EXP(-1.0*X(N)) Y(N)=X(N)*(COS(2*3.14*(N-1)*10.0/K)+ 1 COS(2*3.14*(N-1)*4.0/K)) 11 write (1,20) N,Y(N) DO 12 M=1,K A(M)=0 B(M)=0 DO 13 N=1,K-1 A(M)=A(M)+Y(N)*COS(2*3.14*(M-1)*(N-1)/K) 13 B(M)=B(M)+Y(N)*SIN(2*3.14*(M-1)*(N-1)/K) A(M)=A(M)/K B(M)=B(M)/K M2=M/2 12 write (1,30) M2,A(M2),B(M2) 10 FORMAT(1x,I2) 20 FORMAT(1x,I2,2x,F10.5) 30 FORMAT(1x,I2,2x,F10.5,2x,F10.5) close (unit=1) STOP