Nuclear Magnetic Resonance ANIMATED ILLUSTRATIONS MS Powerpoint Presentation

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 http: //ugc-inno-nehu. com/links_from_web. html

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

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

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. )

PEAK to PEAK PULSE Amplitude PULSE WIDTH

Free Induction Digitized Received Analog Signal Analog to Digital Converter ADC FID analog signal FID digitized points Digitized Signal

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 Pulsed detection mode FT Real Frequency Domain Spectra after FT Similar to the CW mode Spectra

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

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

52341 Probe & sample Transmitter ON time Receiver OFF time Crossed Diodes Receiver 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 Receiver Silent or dead time DATA acquisition starts at this time

Signal level Noise Long T 2 Short T 2 Achieving a Sharp signal Level 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

OH-CH 2 -CH 3 Acidic medium: spin coupling for OH protons do not show up 3. 61 ppm 5. 24 ppm OH CH 2 CH 3 1. 13 ppm 0 TMS δ= 0 ppm Moderate Resolution HR PMR Spectrum δ= 1. 13 ppm 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.

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