| a |
Nuclear spin wavefunction (eigenfunction of  )
for the mI = +½ state of a spin -½
nucleus
|
| aE |
The Ernst angle (for optimum sensitivity) |
| b |
Nuclear spin wavefunction (eigenfunction of )
for the mI = _ ½ of a spin
-½ nucleus
|
| gX |
Magnetogyric ratio of nucleus X |
| dX |
Chemical shift (for the resonance) of nucleus of element X (positive
when the sample resonates to high frequency of the reference). Usually
in ppm (footnote 3). Further information
regarding solvent, references, or nucleus of interest may be given
by superscripts or subscripts or in parentheses. |
| Dn |
Population difference between nuclear states (Dn0
at Boltzmann equilibrium) |
| Dd |
Change or difference in d |
| Dn½ |
Full width in frequency units of a resonance line at half-height |
| Ds |
Anisotropy in s
[ Ds = sZZ
_ ½ ( sXX
+ sYY ) ] (footnote
4). (see also z ) |
| Dc |
(i) Susceptibility anisotropy 
;
(ii) difference in electronegativities |
| e0 |
Permittivity of a vacuum |
| z |
Anisotropy in shielding (footnote
4), expressed as sZZ
_ siso.
(see also Ds ) |
| h |
(i) Nuclear Overhauser enhancement (so that the nuclear
Overhauser effect is 1 + h );
(ii) tensor asymmetry factor (e.g. in s
); (iii) viscosity |
| k |
Skew of a tensor. (see also footnote
7) |
| q |
Angle, especially for that between a given vector
and B0 |
| m |
(i) Magnetic dipole moment (component mz
along B0);
(ii) electric dipole moment |
| m0 |
Permeability of a vacuum |
| mB |
Bohr magneton |
| mN |
Nuclear magneton |
| nj |
Larmor precession frequency of nucleus j (usually given
in MHz) |
| n0 |
(i) Spectrometer operating frequency;
(ii) Larmor precession frequency (general, or of bare nucleus) |
| n1 |
Frequency of 'observing' RF magnetic field B1
(to be distinguished from its strength, gB1,
for which the symbol W1
is recommended) |
| n 2 |
Frequency of 'irradiating' RF magnetic field B2
(to be distinguished from its strength, gB2,
for which the symbol W2
is recommended) |
| XX |
Resonance frequency for the nucleus of element X in a magnetic
field such that the protons in tetramethylsilane (TMS) resonate at exactly 100
MHz |
| r |
Density matrix |
 |
Density operator |
| rij |
Element of matrix representation of |
| s |
Shielding tensor (footnotes 5 and 6) |
| sj |
(Isotropic) shielding constant of nucleus j.
Usually given in ppm. Subscripts may alternatively indicate contributions
to s |
 |
Components of shielding tensor s
parallel and perpendicular to the symmetry axis (axially-symmetric
case) (footnote 5) |
 |
Reduced density operator |
| t |
(i) Time between RF pulses (general symbol);
(ii) lifetime in dynamic NMR usage |
| tc |
Correlation time for molecular-level motion, especially for
isotropic molecular tumbling |
| td |
Dwell time |
| tnull |
Recovery time sufficing to give zero signal after
a 180o pulse |
| tp |
Pulse duration |
| tsc |
Correlation time for relaxation by the scalar mechanism |
| tsr |
Correlation time for spin-rotation relaxation |
 |
Correlation times for molecular tumbling parallel and perpendicular
to the symmetry axis (axially-symmetric case) |
| c |
(i) Magnetic susceptibility (footnote
7); (ii) nuclear quadrupole coupling constant (c
= e2qZZQ/h) |
| wj,
w0, w1,
w2 |
As for nj,
n0, n1,
n2 but for angular
frequencies |
| W |
Span of a tensor |
| W1,
W2 |
Nutation angular frequencies, i.e. RF magnetic fields
expressed in angular frequency units, for a nucleus of magnetogyric
ratio g (W1
= _g B1,
W2 = _g
B2) |
