Proton radioactivity — spherical and deformed

Abstract

The proton drip line defines one of the fundamental limits to nuclear stability. Nuclei lying beyond this line are energetically unbound to the emission of a constituent proton from their ground states.

For near-spherical nuclei in the region of the drip line between Z=69 (Tm) and Z=81 (T1), proton decay transition rates have been shown to be well reproduced by WKB calculations using spectroscopic factors derived from a low-seniority shell model calculation [2]. Another approach using spectroscopic factors obtained from the independent quasiparticle approximation has also proved successful in this region [3]. These interpretations have allowed the extraction of nuclear structure information from nuclei well beyond the proton drip line.

The rare-earth proton emitters ¹⁴¹Ho and ¹³¹Eu have recently been observed [4], and their decay rates can only be explained by assuming large deformation for these nuclei. In addition to providing information on the wavefunctions and deformations of these nuclei, these results offer the opportunity to study the phenomenon of quantum mechanical tunneling through a deformed potential barrier.