Crystal field effects in the compounds RbFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO and CsFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO

\u3cp\u3eMössbauer experiments on the compounds RbFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO and CsFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO have been performed in the temperature region of 4.2 to 300 K. The temperature dependence of the center shift and the quadrupole splitting is reported. A qualitative analysis of these data indicates an orbital-doublet ground state for the octahedrally coordinated ferrous ion. This is confirmed by the results from experiments in an applied magnetic field. A quantitative analysis of the quadrupole splitting data, using the crystal field model, results in the assignment of a singlet 685±50 cm\u3csup\u3e-1\u3c/sup\u3e above the orbital-doublet. The rhombic distortion will lift the degeneracy of the orbital ground state by a splitting of no more than 30 cm\u3csup\u3e-\u3c/sup\u3e. Single-crystal absorbers of RbFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO were measured along the crystal axes, as well as in several directions within the bc plane, in order to determine the principal axes of the electric field gradient tensor (EFG). Additional experiments were performed in the paramagnetic region, by the application of an external magnetic field, and in the magnetically ordered region. Analysis of the spectra results in the assignment of the Cl\u3csub\u3eI\u3c/sub\u3eFeCl\u3csub\u3eI\u3c/sub\u3e axis as the maing axis of the EFG tensor.\u3c/p\u3