where:

E is the energy difference between spin states

h is Planck's constant

is the frequency of the B₁ field

B_e is a small magnetic field generated by the circulation of electrons of the molecule (see below)

B_o is the strength of the external homogeneous magnetic field

(gyromagnetic ratio) is a constant which is a property of the particular nucleus

(Discussed in Spin states)

(obtained by dividing eq 1 by h)

(Discussed in Spin states)

( - _TMS) is the frequency difference between the resonance of the signal of interest and the resonance of TMS. Note that ( - _TMS) will always be in units of Hz (from 1 Hz to a few thousand Hz).
is the center frequency of the B₁ field in megahertz (MHz).
If B_o = 7.05 T, = 300 MHz for ¹H nuclei or 75 Mz for ¹³C nuclei.
If B_o = 11.75 T, = 500 MHz for ¹H nuclei or 125 Mz for ¹³C nuclei.

(Discussed in Chemical shift)

Sample Calculations