Mass Measurement on the r p -Process Waiting Point K r 72

The mass of one of the three major waiting points in the astrophysical $rp$ process $^{72}\mathrm{K}\mathrm{r}$ was measured for the first time with the Penning trap mass spectrometer ISOLTRAP. The measurement yielded a relative mass uncertainty of $\ensuremath{\delta}m/m=1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ ($\ensuremath{\delta}m=8\text{ }\text{ }\mathrm{k}\mathrm{e}\mathrm{V}$). $^{73,74}\mathrm{K}\mathrm{r}$, also needed for astrophysical calculations, were measured with more than 1 order of magnitude improved accuracy. We use the ISOLTRAP masses of $^{72--74}\mathrm{K}\mathrm{r}$ to reanalyze the role of $^{72}\mathrm{K}\mathrm{r}$ (${T}_{1/2}=17.2\text{ }\text{ }\mathrm{s}$) in the $rp$ process during x-ray bursts and conclude that $^{72}\mathrm{K}\mathrm{r}$ is a strong waiting point delaying the burst duration with at least 80% of its $\ensuremath{\beta}$-decay half-life.