Study of neutron rich Carbon and Oxygen nuclei up to drip line

In-beam$\ gamma$-spectroscopy using fragmentation reactions of radioactive beams have been performed in order to study the structure of excited states in neutron rich oxygen and carbon isotopes. For the produced fragments, $\gamma$-ray energies, intensities and $\gamma-gamma$ coincidences have been measured. The experiment was performed at GANIL. New $\gamma$-lines have been identified and placed in level schemes for $^{17-20}$C. The non observation of any $\gamma$-ray in $^{}$O suggests that their first excited states lie above the neutron threshold. These results are discussed in the framework of shell model calculations.