ABSTRACT
Most of the atomic nuclei possess an intrinsic angular moment, or
spin hI, measured in units of h = h/2π , where h is Planck’s constant, and a nuclear magnetic moment μ= γ hI, which is proportional to the magnitude of the spin. In an external magnetic field B0 the nuclear spin 1/2 has two energy levels corresponding to
its “up” and “down” orientation (Fig. 7.1) and separated by an
interval E = hγB0, where γ is the gyromagnetic ratio, which is a characteristic of each nucleus. An oscillating electromagnetic field
of frequency ν0 applied to the system such that hν0 =E induces a resonant transition between the energy levels. This phenomenon is
called nuclear magnetic resonance (NMR), and ν0 is referred to as
the Larmor frequency.
