CHM1006 - NMR
Lecture 1
NMR spectroscopy
Nuclear - dealing with the property of nuclear spin
Magnetic - interaction of the nuclei with applied magnetic fields
Resonance - excitation of nuclear spins using matched frequencies of radiation
Spectroscopy - ultimately, NMR is just another form of spectroscopy
,Nuclear spin and resonance
Nuclei possess charge
A spinning charge generates a local magnetic field
Certain nuclei also possess spin angular momentum (i)
Spin characterised by the spin quantum number i
i = 0, ½, 1, 3/2, etc
, Greater than ½ = quadrupolar
½ = dipolar
A spinning charge generates a local magnetic field
The nucleus therefore possesses a magnetic dipole moment (μ)
Nuclei may therefore be viewed as behaving like microscopic bar magnets
And therefore have a propensity to align with an external magnetic field
Only those nuclei that possess a magnetic dipole moment may be studied by NMR
In the absence of a magnetic field
- No energy difference between energy levels
- Spins are randomly oriented
In the presence of a magnetic field
- Nonzero delta E
- Spins want to be in their low energy state
- Therefore, slight propensity for spins to align with magnetic field
Lecture 1
NMR spectroscopy
Nuclear - dealing with the property of nuclear spin
Magnetic - interaction of the nuclei with applied magnetic fields
Resonance - excitation of nuclear spins using matched frequencies of radiation
Spectroscopy - ultimately, NMR is just another form of spectroscopy
,Nuclear spin and resonance
Nuclei possess charge
A spinning charge generates a local magnetic field
Certain nuclei also possess spin angular momentum (i)
Spin characterised by the spin quantum number i
i = 0, ½, 1, 3/2, etc
, Greater than ½ = quadrupolar
½ = dipolar
A spinning charge generates a local magnetic field
The nucleus therefore possesses a magnetic dipole moment (μ)
Nuclei may therefore be viewed as behaving like microscopic bar magnets
And therefore have a propensity to align with an external magnetic field
Only those nuclei that possess a magnetic dipole moment may be studied by NMR
In the absence of a magnetic field
- No energy difference between energy levels
- Spins are randomly oriented
In the presence of a magnetic field
- Nonzero delta E
- Spins want to be in their low energy state
- Therefore, slight propensity for spins to align with magnetic field
