The $\beta$2p -decay mechanism of $^{31}$Ar

We have measured the $\beta$-decay of $^{31}$Ar with a high granularity setup sensitive to multiparticle decay branches. Two-proton emission is observed from the isobaric analog state in $^{31}$Cl to the four lowest states in $^{29}$P and furthermore from a large number of states fed in Gamow-Teller transitions. The mechanism of two-proton emission is studied via energy and angular correlations between the two protons. In all cases the mechanism is found to be sequential yielding information about states in $^{30}$S up to 8 MeV excitation energy. Improved data on the $\beta$-delayed one-proton branches together with the two-proton data provide precise information about the $\beta$-strength distribution up to 15 MeV excitation energy. (44 refs).