Rotational cross sections and rate coefficients for e-CO and e-HCN collisions have been calculated in the energy range relevant to dark interstellar clouds by using the close-coupling method. Gordon's technique has been used for solving the coupled Schrodinger equations. Initial rotational levels j = 0, 1, and 2 of CO and HCN have been considered. The rotational cross sections have been calculated in the energy range 0.0006 to 0.1 eV and the rate coefficients in the temperature range 5-100 K. The cross sections and rate coefficients thus obtained have been compared with Born and unitarized time-dependent perturbation calculations.

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A ligand field model for 3d' ions with approximate D31, site symmetry has been developed which satisfactorily explains the fine st,ructure parameters, the E P R spectra, and the magnetic susceptibility. The treatment includes the essent.ia1 features of Jahn-Teller distortion and covalency effects which are found t.0 have import.ant bearing on the nature of the Jahn-Teller distortion. Finally by the spin Hamiltonian formalism of Prycc the g-values and magnetic susceptibility are calculated. At.tempts are made t.o f i t the experiment,al data of optical absorption, g-values, and magnetic susceptibility with a set of parameter values in the theoretical expressions a t different temperatures. Prom this an estimate is made of covalency and Jahn-Teller parametcrs.Es wird ein Ligandenfcldmodcll fiir 3d1-Ioncn mit niiherungsweise Djh-Yunktsymmetrie entwickelt, das die Feinstrukturparanieter, die EPR-Spektrcn und die niagnctische Suszeptibilitat befriedigcnd erklart. Dip Behandlung schlieot die wesent,lichen Charakteristiken der Jahn-Teller-Verzerning und Kovalenzeffektc ein, dic bedcutendcn Ant,eil an der Natur dcr Jahn-Teller-Verzcrrung habcn. Mit dcm Spin-Hamiltonformalismus von Pryce wird der g-Wert und die magnetischc Suszcptibilitat bercchnet. Es werden Versuche gemacht, cxperimentelle Wcrt.e der optischcn Absorption, g-Werte und die magnetische Suszeptibilitat an einen Parametcrsatz in den theoretischcn Ausdriicken bei verschiedencn Ternperahmen anzupassen. Damit werdcn die Kovalenz-und Jahn-Tcllcr-Parameter berechnet.