Properties of low-lying negative-parity states in ${}^{16}\mathrm{C}$

Recent results concerning negative-parity states in ${}^{16}\mathrm{C}$ are analyzed in terms of the shell model and a simple weak-coupling model. We suggest the state at 6.28 MeV is $2^{-}$, and the state near 6.1 MeV is not $3^{-}$, but probably $1^{-}$ ($0^{-}$).

Figure 1

From right to left: The first three levels of ${}^{17}\mathrm{C}$, then the doublets in ${}^{16}\mathrm{C}$ obtained by coupling a $0p_{1/2}$ hole to ${}^{17}\mathrm{C}$, then the first two levels of ${}^{15}\mathrm{C}$. Arrows indicate the preferred formation and decay of the ${}^{16}\mathrm{C}$ states. The left-hand column contains the three experimental states and their decays.

Figure 2

Experimental levels of Ref. [1] (right) and weak-coupling levels (left). This figure uses our relative centroid energies. The first $2^{-}$ states have been aligned, and we have assumed doublet splittings of 0.5 MeV, following Bohlen et al. [3]. Subscripts on $2^{-}$ and $1^{-}$ refer to the ordering before doublet splitting is included.