[en] The title compounds were synthesized and subsequently studied by inelastic neutron scattering (INS). Energy splittings due to the crystalline electric field (CEF) were directly observed for the octahedral LnX₆^3- units in the Cs₂ALnX₆ series. They can be rationalized in terms of crystal-field theory. In the dimer compounds Cs₃Ln₂Br₉ (Ln³⁺ = Tb, Yb) the energy splitting is the result of the combined action of CEF and exchange interactions. (Auth.)