New neutron-deficient isotopes from $^{78}$Kr fragmentation

TL;DR

This study reports the discovery of new neutron-deficient isotopes near the proton drip-line through $^{78}$Kr fragmentation, providing new data on isotope production and cross sections, and identifying potential candidates for two-proton radioactivity.

Contribution

First observation of several new neutron-deficient isotopes via $^{78}$Kr fragmentation, with measurements of production cross sections and insights into fragmentation models.

Findings

Identification of $^{63}$Se, $^{67}$Kr, $^{68}$Kr, and $^{59}$Ge for the first time.

Confirmation that EPAX overestimates cross sections in this mass region.

Potential candidates for ground-state two-proton radioactivity.

Abstract

In an experiment with the BigRIPS separator at the RIKEN Nishina Center, the fragmentation of a $^{78}$Kr beam allowed the observation of new neutron-deficient isotopes at the proton drip-line. Clean identification spectra could be produced and $^{63}$Se, $^{67}$Kr, and $^{68}$Kr were identified for the first time. In addition, $^{59}$Ge was also observed. Three of these isotopes, $^{59}$Ge, $^{63}$Se, and $^{67}$Kr, are potential candidates for ground-state two-proton radioactivity. In addition, the isotopes $^{58}$Ge, $^{62}$Se, and $^{66}$Kr were also sought but without success. The present experiment also allowed the determination of production cross sections for some of the most exotic isotopes. These measurements confirm the trend already observed that the empirical parameterization of fragmentation cross sections, EPAX, significantly overestimates experimental cross sections in this mass region.