1 / 15

The Simple Concept Of NMR

The Simple Concept Of NMR. Sarah Newton University of Oregon Applied Physics. Background. Many applications in Chemistry and Medicine 1940's- First Signs of NMR

steven-castaneda
Télécharger la présentation

The Simple Concept Of NMR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Simple Concept Of NMR Sarah Newton University of Oregon Applied Physics

  2. Background • Many applications in Chemistry and Medicine • 1940's- First Signs of NMR • Bloch, Purcell, and others noticed the H nuclei had magnetic properties. It could absorb RF energy when placed in a field of a strength specific to the identity of the nuclei. • When absorption occurs, the nucleus is described as being in resonance.

  3. Objectives • Simulate different circuits to give the best resonance • Develop a detector Built within constraints: Resonance no higher than 13MHz. • See CW • See Pulsed • Compare and analyze their similarities and differences

  4. Connection to Optics • NMR and Optical Pumping have the same basic concept • Optical Pumping It is a two level system that electronically excites the constituents of a medium into another energy state. i.e. Laser

  5. What is NMR? • Type of Spectroscopy that manipulated the magnetic properties of nuclei within a sample • That manipulation leads to finding the chemical properties and environment contained within the sample.

  6. CW/Pulsed NMR • CW(Continuous Wave) NMR • Experiments have a varying frequency of radiation at constant magnetic field and measuring the absorption of radiation by the different nuclei. • Pulsed(Fourier Transform) NMR • Resonances are not measured one after another but all nuclei are excited at the same time by a radio frequency pulse. • Excited spins emit the absorbed radiation after the pulse. Intensities of several frequencies are calculated and framed into spectrum.

  7. Circuit Sim

  8. Sims Graph

  9. Circuit

  10. Methodology • Magnet is powered up • Sample lowered into quartz vial (connected to the circuit.) • RF gain(from radio receiver) increased to max • Capacitor dials on bridge circuit turned to minimize RF gain • Amps of DC power supply adjusted until a signal becomes visible on the oscilloscope. • The small function generator provides a“wobble” on the coils while the older generator is the driving unit

  11. Intrumentation

  12. Results (What Should have happened) • In the CW -fixed frequency and varying current -Able to observe the resonant signal (“wiggle”) at individual frequencies in succession • In pulsed -A short pulse containing a range of frequencies -All nuclei spins are excited( with a range of frequencies) -Induces a current creating an electrical signal response

  13. Conclusion/Summary • Success!!! Circuit works and is fully functional But.. Due to the strange disappearance and reappearance of resonance at different frequencies we will go back to the drawing board.

  14. Future Work • Simulations • Build a better circuit • Run both CW and Pulse NMR

  15. Acknowledgements • Material Science Institute • Stephen Gregory and Brian Boggs

More Related