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Spectroscopic studies of proton rich nuclei

(september 2012)

When going far from beta stability, the available energy for radioactive decay increases (Qbeta value), and for proton-rich isotopes, the proton separation energy SP decreases.

The decay (\beta+ or electron capture EC) can then populate excited states above SP in the daughter nucleus that can emit a subsequent proton. With increasing excitation energy of populated states, the delayed proton emission (after \beta decay) first concurrences, then replaces, the electromagnetic (\gamma emission) de-excitation. For even more exotic isotopes, the delayed 2- or 3-proton emission becomes possible (\beta-2p. \beta-3p).

Illustration showing a possible decay scheme for very proton-rich nuclei

The isotopes are produced using fragmentation reactions and implantation in a silicon detectors setup, or using ISOL technique and collecting the nuclei inside the detection setup.

The measurement of protons and gamma-rays emitted during the decay process allows to build the decay scheme of those nuclei. This kind of spectroscopic studies allows to investigate a wide range of topics concerning nuclear physics, such as :
- decay half-lives;
- beta transition strengh distribution ;
- ground states mass differences and analog states masse using IMME;
- isospin mixing of proton emitting states;
- search for direct 2-proton emission components (without involving any intermediate state)
- ...