Mass measurements of neutron-rich Rb and Sr isotopes

Abstract

We report on the mass measurements of several neutron-rich $\mathrm{Rb}$ and $\mathrm{Sr}$ 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 ${}^{98,99}\mathrm{Rb}$ and ${}^{98-100}\mathrm{Sr}$ have been determined with a precision of $6-12\mathrm{keV}$, making their uncertainty negligible for r-process nucleosynthesis network calculations. The mass of ${}^{101}\mathrm{Sr}$ has been determined directly for the first time with a precision eight times higher than the previous indirect measurement and a deviation of $3\ddot{I}ƒ$ when compared to the Atomic Mass Evaluation. We also confirm the mass of ${}^{100}\mathrm{Rb}$ from a previous measurement. Furthermore, our data indicates the existance of a low-lying isomer with $80\mathrm{keV}$ excitation energy in ${}^{98}\mathrm{Rb}$. 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.

8 pages, 5 figures