Spectroscopic Investigation of Even-Even Neutron-Deficient Gd Isotopes

Properties of levels in

{}^{146}{Gd}

{}^{148}{Gd}

, and

{}^{150}{Gd}

have been investigated both by observing the electron-capture decay of

{}^{148}{Tb}

and

{}^{150}{Tb}

as well as the

γ

transitions following the (

α, xn

) reactions on

{}^{144}{Sm}

and

{}^{148}{Sm}

targets. Decay schemes were constructed or confirmed. The angular distributions of the

γ

lines with respect to the beam direction enabled spin assignments for most states. Searches for isomerism revealed lifetimes of

T_{\frac{1}{2}} = 17.3 \pm 2.0

nsec and

T_{\frac{1}{2}} = 9.1 \pm 2.0

nsec, respectively, for the

8^{+}

2689-keV level in

{}^{148}{Gd}

and the

6^{+}

2981-keV state in

{}^{146}{Gd}

and indicate a particle character for these states. An upper limit of 5 nsec was derived for the half-lives of any level reached in

{}^{150}{Gd}

. The decay schemes of

{}^{148}{Gd}

and

{}^{150}{Gd}

are similar to those of the neighboring neutron-deficient nuclei, e.g.

{}^{148}{Sm}

and

{}^{146}{Nd}

. The low-lying negative-parity states observed may represent a collective sequence based on a

3^{-}

state.

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