Experimental studies of nuclei beyond the proton drip line by tracking technique

A novel experimental technique for measurements of in-flight decays of proton-unbound nuclei with pico-second lifetimes is described on the examples of the recent discovery of ¹⁹Mg and its two-proton (2p) radioactivity and the study of the reference 2p decay of the known isotope ¹⁶Ne . The method of measurements of 2p decays in flight by tracking all fragments with micro-strip detectors has also proven to be a potent tool for obtaining valuable spectroscopic information on exotic isotopes like ¹⁹Mg or ¹⁶Ne . Systematic studies of other 2p emitters predicted theoretically are foreseen with this powerful technique whose sensitivity is larger by factor of 20-30 in comparison with a conventional invariant-mass method. Information about the respective one-proton unbound subsystems can be obtained at the same time by evaluating proton-heavy-fragment correlations, which is illustrated on the example of the spectroscopy of ¹⁵F . This finding opens a way for systematic studies of exotic nuclei beyond the proton drip line, e.g., ⁶⁹Br . The properties of such nuclei may be important for the understanding of the element abundance in the Universe and may be used as input data for modeling the rp-process in various astrophysical sites.