Mass measurements of neutron-rich Rb and Sr isotopes

We report on the mass measurements of several neutron-rich $\mathrm{R}\mathrm{b}$ and $\mathrm{S}\mathrm{r}$ isotopes in the $A\approx 100$ region with the TITAN Penning-trap mass spectrometer. Using highly charged ions in the charge state $q=10+$, the masses of ${}^{98,99}\mathrm{R}\mathrm{b}$ and ${}^{98-100}\mathrm{S}\mathrm{r}$ have been determined with a precision of $6-12\mathrm{k}\mathrm{e}\mathrm{V}$, making their uncertainty negligible for r-process nucleosynthesis network calculations. The mass of ${}^{101}\mathrm{S}\mathrm{r}$ has been determined directly for the first time with a precision eight times higher than the previous indirect measurement and a deviation of $3\sigma$ when compared to the Atomic Mass Evaluation. We also confirm the mass of ${}^{100}\mathrm{R}\mathrm{b}$ from a previous measurement. Furthermore, our data indicates the existance of a low-lying isomer with $80
$\mathrm{k}\mathrm{e}\mathrm{V}$$excitationenergyin$^{98}$\mathrm{R}\mathrm{b}$$. We show that our updated mass values lead to minor changes in the r-process by calculating fractional abundances in the $A\approx 100$ region of the nuclear chart.