Penning trap mass measurement of ${}^{72}\mathrm{Br}$

The Low Energy Beam and Ion Trap (LEBIT) Penning trap mass spectrometer was used to perform an improved-precision mass measurement of ${}^{72}\mathrm{Br}$ and the low-lying isomeric state, ${}^{72m}\mathrm{Br},$ giving mass excesses of $-59062.2\left(1.0\right)\mathrm{keV}$ and $-58960.9\left(1.2\right)\mathrm{keV}$, respectively. These values are consistent with the values from the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)] and the Nubase2012 evaluation of nuclear properties [Chin. Phys. C 36, 1157 (2012)]. The uncertainties on the mass of the ground state and isomeric state have been reduced by a factor of seven.

Figure 1

Schematic diagram showing the major elements of the gas cell and LEBIT facility.

Figure 2

A sample time-of-flight cyclotron resonance used for the determination of the frequency ratio of ${\nu }_c{(}^{72}{\text{Br}}^{+})/{\nu }_{\text{ref}}^{\text{int}}$. This example of a bromine resonance shows both the ground-state cyclotron resonance (right) and the isomer ${}^{72m}\mathrm{Br}{}^{+}$ (left). The solid red (gray) curve represents a weighted fit of two theoretical profiles [10] to account for the production of each state.