Study of low-lying resonant states in $^{16}$F using an $^{15}$O radioactive ion beam

Among the A=16, T=1 isobaric triad, many states in $^{16}$O and $^{16}$N have been well established, but less has been reported about $^{16}$F. Experimental studies with stable beams have established spin-parity values for the first four low-lying states of $^{16}$F, but only upper limits or rough estimates of their level widths have been reported. The spins and parities of the low-lying states have been found to be 0$^{-}$, 1$^{-}$, 2$^{-}$, and 3$^{-}$ in ascending order in energy, and are believed to have $^{15}$O core-single proton configurations of 1p$_{1/2}^{-1}$ 2s$_{1/2}$ for the 0$^{-}$, 1$^{-}$, and 1p$_{1/2}^{-1}$ 1d$_{5/2}$ for the 2$^{-}$, 3$^{-}$. A recently developed $^{15}$O (T$_{1/2 }$= 122 sec.) radioactive ion beam from the BEARS (Berkeley Experiments with Accelerated Radioactive Species) facility was used to study the structure of $^{16}$F using $^{15}$O+p elastic scattering and the Thick Target Inverse Kinematics method on a polyethylene target. The level widths of the first four states in $^{16}$F were determined using R-matrix analysis, and our results show that the 0$^{-}$ state has a level width of 22.8 $\pm $ 14.4 keV, and that the broad 1$^{-}$ state has a width of 103 $\pm $ 12 keV. The level width of the 2$^{-}$ state is found to be 4.0 $\pm $ 2.5 keV which is much narrower than the compiled value, while 15.1 $\pm $ 6.7 keV for the 3$^{-}$ state is in good agreement with previous studies.