Absolute spectroscopic factors from neutron knockout on the halo nucleus ${}^{15}\mathrm{C}$

An accurate determination of the partial cross sections to four final states in the ${}^9\mathrm{Be}\left({}^{15}\mathrm{C},{}^{14}\mathrm{C}\right)X$ reaction has been carried out at $103\mathrm{MeV}∕\text{nucleon}$. The cross section of $101\left(5\right)\text{mb}$ to the ${}^{14}\mathrm{C}{0}^{+}$ ground state is of special interest. Relative to the theoretical cross section calculated on the basis of the spectroscopic factor from effective-interaction theory, this amounts to a quenching factor $R_s=0.90\left(4\right)\left(5\right)$. Here the first number in parentheses is the experimental error, and the second is the error on the theoretical unit (reaction) cross section. The result gives support to the idea that weakly bound halolike states have quenching factors that approach unity, in contrast to factors of $0.5–0.6$ characteristic of well-bound states in nuclei near stability.

Figure 1

The $\gamma$-ray spectrum from the reaction ${}^9\mathrm{Be}\left({}^{15}\mathrm{C},{}^{14}\mathrm{C}+\gamma \right)X$ (filled circles) transformed, event by event, to the projectile frame at midtarget. The response functions for each gamma energy arising from this analysis have been obtained in the Monte Carlo simulation. The approximately exponential component is the continuum contribution ascribed to neutrons and gamma rays from the target. Its intensity and shape has been taken from [17]. The inset shows the simplified level scheme of ${}^{14}\mathrm{C}$ indicating the states populated in this reaction.