The Magnetic Susceptibility of Free Atoms

The diamagnetic contribution follows from Larmor s theorem (389) which states (For a proof of this theorem, see reference (028), p. 22.) For an atom in a magnetic field, the motion of the electrons isf to a first approximation in H, the same as a motion in the absence of H except for the superposition of a common precession of angular frequency u)L = ell/2mc = IIp.fi/ti. The angular momentum of an atom is, from equation 7  

Given a permanent atomic moment, derivation of the paramagnetic contribution assumes that the energy of separation of the lowest from the first excited electronic levels in the atom or ion are either small or large compared to kT. Van Vleck (628) has shown that the matrix elements between levels of large separation, the high- 

The spectroscopic splitting factor g, also referred to as the Lande (c86) g factor, falls within the limits of 1 g 2, where g = 1 corresponds to S = 0, and g = 2 to a spin-only (L = 0) magnetic 

Usually the ground state is a minimum or a maximum of J, depending on whether the multiplet is regular or inverted, and the second or first term, respectively, of equation 17 vanishes. 

In summary, the magnetic susceptibility for an atom with multiplet separation A kT Em is 

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