The standard example of Van Vleck paramagnetism are europium(III) oxide (Eu 2 O 3) salts where there are six 4f electrons in trivalent europium ions. The ground state of Eu that has a total azimuthal quantum number j = 0 and Curie's contribution ( C 0 / T ) vanishes, the first excited state with j = 1 is very close to the ground state at 330 K and contributes through second order corrections as showed by Van Vleck. A similar effect is observed in samarium salts (Sm ions). In the actinides, Van Vleck paramagnetism is also important in Bk and Cm which have a localized 5f 6 configuration.