First high resolution study of a T$_{z} = -5/2$ nucleus

We have studied in great detail the $\beta$-decay of the T$_{z}=-5/2$ drip line nucleus $^{31}$Ar. This decay with a $Q_{\beta}=18.5$ MeV is open to the following decay modes: $\beta\gamma , \beta$ p, $\beta$ 2p, $\beta$ 3p, $\beta\alpha$ and $\beta$ p $\alpha$. This work aiming to study the mechanism of $\beta$-delayed two proton emission has carefully checked all possible decay modes. As result of a series of experiments done at ISOLDE (IS339) we have identified about twenty different two- proton branches from the excited states in $^{31}$Cl where the main decay mechanism is the sequential one. Limits for the $\beta$-3p branch and missing strength from the IAS are discussed. (20 refs).