| a or A |
Hyperfine (electron-nucleus) coupling constant |
| Aq(l,m) |
The mth component of an irreducible tensor
of order l representing the nuclear spin operator for an
interaction of type q |
| B |
Magnetic field (strictly the magnetic flux density or magnetic
induction) |
| B0 |
Static magnetic field of an NMR spectrometer |
| B1, B2 |
Radiofrequency magnetic fields associated with frequencies
v1, v2 |
| BL |
Local magnetic field (components BxL
, ByL , BzL
) of random field or dipolar origin |
| C |
Spin-rotation interaction tensor |
| CX |
Spin-rotation coupling constant of nuclide X |
| D |
Dipolar interaction tensor |
| D |
Dipolar coupling constant between two
nuclei (say 1 and 2), (m0/4p)g1g2(h/4p2)r12-3,
in frequency units (footnote 1). |
| DC |
Nuclear receptivity relative to that of the carbon-13 nucleus
|
| Dp |
Nuclear receptivity relative to that of the proton (hydrogen-1
nucleus) |
| E |
Electric field strength |
| F |
Spectral width |
F1, F2
(or f1,
f2) |
The two frequency dimensions of a two-dimensional spectrum (use
F3 etc. for higher orders) |
 |
Nuclear spin operator for a group, G, of nuclei (components  )
|
| FG |
Magnetic quantum number associated with |
| g |
Nuclear or electronic g factor (Landé splitting factor) |
| G |
Magnetic field gradient amplitude |
| Hij |
Element of matrix representation of Hamiltonian operator (in
energy units); subscripts indicate the nature of the operator |
 |
Nuclear spin operator for nucleus j
(components  )
|
 |
'Raising' and 'lowering' spin operators for nucleus
j |
| Ij |
Magnetic quantum number associated with |
| J |
Indirect coupling tensor |
| nJ |
Nuclear spin-spin coupling constant through n
bonds (usually given in frequency units) Parentheses may be used
(for example) to indicate the species of nuclei coupled, e.g. J(13C,
1H) or, additionally, the coupling path, e.g. J(POCF).
Where no ambiguity arises, the elements involved can be, alternatively,
given as subscripts, e.g. JCH. The nucleus of
higher mass should be given first |
| J(w) |
Spectral density of fluctuations at angular frequency
w. Subscripts and superscripts
to J may be used to indicate the relevant quantum number
change (0, 1 or 2) or the order and component of the relevant tensor
quantities. |
| nK |
Reduced nuclear spin-spin coupling constant (see the
notes concerning nJ), Kjk =
4p2 Jjk
/ hgj gk |
| L |
Angular momentum |
| mj |
Eigenvalue of 
(magnetic component quantum number) (footnote
2) |
| mtot |
Total magnetic component number for a spin system
(eigenvalue of  )
(footnote 2) |
| mtot(X) |
Total magnetic component quantum number for X-type nuclei (footnote
2) |
| M0 |
Equilibrium macroscopic magnetization per volume of a spin system
in the presence of B0 |
| Mx , My , Mz |
Components of macroscopic magnetization per volume |
| Mn |
nth moment of spectrum (M2
= second moment, etc.) |
| na , nb |
Populations of the a
and b spin states |
| N |
Total number of nuclei of a given type per volume
in the sample |
| q |
Electric field gradient tensor in units of the elementary
charge (principal components qXX, qYY,
qZZ) (see also V) |
| Q |
eQ is the nuclear quadrupole moment, where
e is the elementary charge |
| R1X |
Spin-lattice (longitudinal) relaxation rate constant for nucleus
X |
| R2X |
Spin-spin (transverse) relaxation rate constant for
nucleus X |
| R1rX |
Spin-lattice relaxation rate constant in the rotating frame
for nucleus X |
| S |
Signal intensity |
 |
Electron (or, occasionally, nuclear) spin operator;
cf.  |
| t1, t2 |
Time dimensions for two-dimensional NMR |
| Tc |
Coalescence temperature for signals in an NMR spectrum |
| T1X |
Spin-lattice (longitudinal) relaxation time of the X nucleus
(further subscripts refer to the relaxation mechanism) |
| T2X |
Spin-spin (transverse) relaxation time of the X nucleus (further
subscripts refer to the relaxation mechanism) |
| T2* |
Net dephasing time for Mx or My
(including contribution from magnetic field inhomogeneity) |
| T1rX |
Spin-lattice relaxation time of the X nucleus in the frame of
reference rotating with B1 |
| Td |
Pulse (recycle) delay |
| Tac |
Acquisition time |
| Tq(l,m) |
The mth component of an irreducible tensor
of order l representing the strength of an interaction of
type q |
| V |
Electric field gradient tensor. V
= eq,
where e is the elementary charge |
| Vab |
Elements of Cartesian electric field gradient tensor |
| W0, W1, W2 |
Relaxation rate constants (transition probabilities per time)
between energy levels differing by 0, 1, and 2 (respectively) in
mtot; especially, but not uniquely, for systems
of two spin -1/2 nuclei |
| Wrs |
Transition probability between spin states r
and s |
