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

摘要

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 ~(15)F. 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.