Yrast γ-ray spectroscopy of the neutron rich isotopes<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Co</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>6</mml:mn><mml:mn>1</mml:mn><mml:mo>,</mml:mo><mml:mn>6</mml:mn><mml:mn>3</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>

The neutron rich nuclei $^{61,63}\mathrm{Co}$ have been studied using the reactions $^{16}\mathrm{O}$${(}^{48}$Ca,p2n${)}^{61}$Co and $^{18}\mathrm{O}$${(}^{48}$Ca,p2n${)}^{63}$Co at a bombarding energy of 110 MeV. Discrete \ensuremath{\gamma} rays from the channels of interest were investigated using prescaled \ensuremath{\gamma} singles, charged-particle--\ensuremath{\gamma}, neutron--charged-particle--\ensuremath{\gamma}, and charged-particle--\ensuremath{\gamma}--\ensuremath{\gamma} coincidence techniques. Decay schemes, with level spins deduced from two-point angular distribution data, are presented together with some approximate information on apparent state lifetimes. The experimental results are compared with previous light ion data for these systems and with theoretical shell model predictions. These data represent the first study of medium to high spin states in these nuclei. \textcopyright{} 1996 The American Physical Society.

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