1. (Instrument part)
Thanundon Kongnok M

2. OUTLINE Introduction : Type of NMR Spectroscopy
What is NMR ?
Nuclear spin
Resonance frequency
Type of NMR Spectroscopy
CW NMR Spectroscopy
FT NMR Spectroscopy
Pulsed Fourier Transform NMR Spectroscopy
NMR sequential steps
Instrument
Conclusion

3. What is NMR ?
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a magnetic field absorb and re-emit electromagnetic radiation at resonance frequency.

4. Net spin of a nucleus Nucleus has NO spin. 12C (0), 18O (0), 32S (0)
Nucleus has a half-integer spin. 1H (½), 13C (½), 31P (½) NMR can detect
Nucleus has an integer spin 2H (1), 14N (1)
B5 o8

5. Splitting of nuclei spin states
Gamma is gyromagnetic ratio constant
α spin state
ΔE = hγB0/2π

6. larmor frequency hυ=ΔE = hγB0/2π
The magnetic moment of each nucleus precesses around B0.
The frequency of this precession (larmor frequency ) is equivalent to the resonance frequency (υ) of the nucleus and the energy difference between the two levels
(larmor frequency about 60–1000 MHz)
Depends on the strength of the magnetic field and the magnetic properties of the isotope of the atoms
hυ=ΔE = hγB0/2π

7. Type of NMR Spectroscopy
Continuous wave NMR Spectroscopy
Varying the frequency of radiation at constant magnetic field and measuring the absorption of radiation by the different nucle
FT NMR Spectroscopy (better resolution and sensitivity)
In FT-NMR all nuclei are excited at the same time by a radio frequency pulse.
Radio frequency pulse : if the radiation is emitted as a very short pulse. A short radio frequency pulse contains many frequencies in a broad band around υ0 .

8. FT-NMR sequential steps
Steps 1 : The alignment (polarization) of the magnetic nuclear spins in an applied, constant magnetic field H
Gamma is gyromagnetic ratio constant
Nβ/Nα = exp(ΔE/kT)

9. FT-NMR sequential steps
Step 2 : The perturbation of the alignment by employing radio frequency (RF) pulse “90° pulse”.
Transversal magnetization (dark blue) can now be created by applying an additional magnetic field B1 (red) which is perpendicular to B0. This B1 field is the radiofrequency pulse mentioned above. If the radiation frequency is equal to the larmor frequency of the nuclei the field causes a rotation of the equillibrium magnetization Mz (light blue) around the x axis (cross product, Beff=B1). You can completely transform the z magnetization to y magnetization if the duration of the pulse is sufficiently long. In this case the pulse is called an 'excitation pulse' or '90° pulse' (obviously because the rotation angle of the magnetization is 90°).
dM/dt = gamma* [M × Beff]
Beff = (B0 + (w0/ gamma)) + B1 = B1

10. FT-NMR sequential steps
Step 3 : After 90° pulse, each spin precesses with its own larmor frequency around the z axis and induces a signal in the receiver coil. The signal decays due to relaxation and is therefore called free induction decay (FID).

11. FT-NMR sequential steps
Step 3 : Fourier Transformation FT

12. Instrument

13. Instrument • An intense, homogeneous and
stable magnetic field (magnet + shim)
• A “probe” which enables the coils
used to excite and detect the signal
to be placed close to the sample
• High-power RF transmitter/s
capable of delivering short pulses
(RF source + RF Amplifier)
• A sensitive receiver to amplify the NMR signals (RF Detector)
• A Digitizer to convert the NMR signals into a form which can be
stored in computer memory
• A “pulse programmer” to produce precisely timed pulses and delays
• A computer to control everything and to process the data
To optimize the sensitivity this coil needs to be (1) as close as possible to the sample; (2) tuned to resonant at the Larmor frequency of the nuclei being detected and (3) matched to maximize power transfer between the probe and the transmitter and receiver.

14. Instrument
Superconducting Magnet

15. Instrument The NMR sample The sample should be dissolved in a solvent
The NMR sample is prepared in a thin-walled glass tube - an NMR tube.

16. Sensitivity & Price $ USD 7 - 9.4 - 11.7 - 14 - 18.7 - 21 Tesla
MHz

17. A 900MHz NMR instrument with a 21
A 900MHz NMR instrument with a 21.1 T magnet at HWB-NMR, Birmingham, UK

18. Conclusion
Can provide detailed information about the structure, dynamics, chemical environment and identical functional groups of molecules .
Most frequently, NMR spectroscopy is used by chemists and biochemists to investigate the properties of organic molecules
NMR spectrometers have expensive liquid helium-cooled superconducting magnet

19. Thank you for your attention