Proton instability of⁷³Rb

The study of the stability of an astrophysically interesting nucleus73Rb was performed by searching itsβ + and proton decay at the ISOLDE facility at CERN. Light rubidium isotopes were produced in a spallation reaction of a niobium target induced by a pulsed 1 GeV proton beam. The previously reported proton-unbound character of73Rb was confirmed and the upper limit for its production cross-section was reduced by more than one order of magnitude.