The problem of an isolated ion with a total angular momentum J in a cu
bic metal is analyzed by the technique of Abrikosov pseudofermions. A
system of generalized kinetic equations is constructed. The particular
example J = 5/2 is studied in the case in which the ground state is t
he quartet GAMMA8 (CeB6). The central peak in the susceptibility can b
e described by a sum of two Lorentzians, one of which is narrower and
higher than the other. This multimode behavior is shown to be a genera
l phenomenon when a degenerate multiplet is not a doublet and does not
constitute all the states of the system.