The decay properties of the neutron deficient nuclei $ sp{144}$Gd, $ sp{142}$Gd, $ sp{ rm 141g}$Gd, $ sp{ rm 141m}$Gd and $ sp{140}$Gd are investigated in detail for the first time and the new beta decaying isomers $ sp{ rm 141g,m}$Gd, $ sp{141}$Tb(A) and $ sp{140}$Gd are discovered. A gas-jet recoil-transport system and a conversion electron spectrometer are designed and constructed in order to measure the electromagnetic transitions emitted following their decay. Levels schemes are deduced for the daughter nuclei $ sp{144}$Eu, $ sp{142}$Eu, $ sp{141}$Eu, $ sp{140}$Eu, and $ sp{141}$Gd and spin-parity assignments are established for several states. The decay half-life of these nuclei is also measured. / The deduced information is discussed in the general context of the Z $ geq$ 50, N $ leq$ 82 mass region. The low lying structure of the N = 76, 77, 78, 79, 81 and 82 isotones is compared to the predictions of theoretical calculations using either spherical BCS or deformed Hartree-Fock plus BCS formalism with a semi-realistic interaction derived from the Tabakin potential. Contributions to original knowledge are outlined in Chapter V.

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