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-5 NMR Spectrometer: Instrumentation

2. Pulse widths could be 10-2 μs
100 MHz Electro-magnet/Permanent magnet Systems
Z-direction
Supercon magnet systems above 100MHz up to 900MHz as known currently
Z-direction
Magnet Current source
Superconducting current carrying coils

3. Pulsed Mode of Detection
CW RF Oscillator mw power
CW Mode of detection
Pulsed Mode of Detection
RF Crystal Detector
Display/Record
Pulsed RF Transmitter
Signal receiving and detection
High gain RF receiver/detector
Probe with sample coil and sample in Magnetic Field
Time domain signal to computer for FFT
Signal generation
Display monitor/Plotter

4. Flowing Current and Induced Magnetic Fields in a Solenoid
Electrons (Blue Circles) Move and the Conventional Current Flows in the Opposite direction.
The MOTION of the (red) isolated (?) northpoles indicate the induced field distributions and in reality there are no lines existing for the LINES of FORCES (as drawn in the previous slide. It is a virtual line and LOCUS of the point North pole.)

5. PEAK to PEAK PULSE Amplitude
PULSE WIDTH
PEAK to PEAK PULSE Amplitude

6. Analog to Digital Converter
Free Induction Digitized
Analog to Digital Converter
A D C
Received Analog Signal
Digitized Signal
FID analog signal
FID digitized points

7. Frequency Domain Spectra after FT
All the signal shapes have been calculated in MS EXCEL
In practice FFT program calculates Frequency domain spectra from the time domain signal
Integration
FID
FT Imag.
Time Domain Signal
FT Real
Pulsed detection mode
Frequency Domain Spectra after FT
Similar to the CW mode Spectra

8. Phase Sensitive Detector
HR NMR in Liquids 100W NMR of Solids 3KW PP Matched 50 Ω
Sample coil in the Probe with sample
Power Amplifier
High Power RF Pulses to Probe
Spectrum to display monitor/Plotter
Rectangular RF Pulse
FID
CW RF Source
Gate
Low noise RF Preamplifier
DC Pulse
computer [FFT]
High Gain Signal Amplifier
Pulse Programmer
Time Domain signal
Phase Sensitive Detector
ADC
Reference Signal
Transmitter
Receiver

9. Sample tube with sample
Basic Probe unit is a Resonance Circuit with tunable split capacitors configuration for matching.
Sample tube with sample
Low noise pre-amplifier /high gain receiver/PSD/Digital computer/Plotter
High-Power pulse transmitter
RF Bridge (Hybrid Junction)
RF Source (sweep generator)
RF Signal receiver- detector
Scope
Receiver off time
Pulsed RF mode
CW Mode
CW Mode
50Ω

10. DATA acquisition starts at this time5 2 3 4 1
Probe & sample
Crossed Diodes
Transmitter ON time
Receiver
Receiver Silent or dead time
Receiver OFF time
DATA acquisition starts at this time
After the RF pulse, the FID is the impulse response from the sample spin system. The pulsing and FID can be repeated and added to acquire the averaged signal for better signal to noise ratio

11. Signal level
Noise Level
Achieving a Sharp signal depends on the homogeneity of the magnetic filed: Shimmimng the magnetic field using gradient correction coils and sample spinning are the provisions in the spectrometer system for improving the homogeneity
Long T2
Short T2

13. OH-CH2-CH3
Acidic medium: spin coupling for OH protons do not show up
CH3
3.61 ppm
5.24 ppm
1.13 ppm
CH2 OH
TMS δ= 0 ppm
Moderate Resolution
δ= 1.13 ppm
HR PMR Spectrum
This calculated and simulated [60 MHz] spectrum has the chemical shift and frequency values as obtained from a real NMR spectrum of alcohol. The above figure plotted using MS Excel application and line drawing from MS WORD drawing tools. High Resolution spectrum as shown above would be possible with good homogeneity of the magnetic field.

14. In the Pulsed Field Gradient PFG and Magnetic Resonance Imaging MRI techniques calculated field gradient are externally superposed.
The inherent unwanted and incidental inhomogeneities are reduced by Shimming and sample spinning
NMR frequency will vary linearly along the length.
3 lines inside
6 lines inside
Along the length same nmr frequency for the sample
Linear Field Gradient along z-axis.
Equal number of lines pass through fixed area of cross section along the length