Angular correlation measurements for the $\alpha +{}^6\mathrm{He}$ decay of ${}^{10}\mathrm{Be}$

The $\alpha +{}^6\mathrm{He}$ decay of ${}^{10}\mathrm{Be}$ has been studied via the ${}^7\mathrm{Li}\left({}^7\mathrm{Li},\alpha {}^6\mathrm{He}\right)\alpha$ reaction at $58\mathrm{MeV}$. The excitation energy of the ${}^{10}\mathrm{Be}$ nucleus was determined following the coincident detection of the $\alpha$ and ${}^6\mathrm{He}$ decay products. A study of the fragment angular correlations has provided a spin assignment consistent with the previously reported value of $3^{-}$ for the $10.15\mathrm{MeV}$ state in ${}^{10}\mathrm{Be}$. A tentative assignment of $\left(4^{+}\right)$, $6^{+}$ is proposed for the $11.76\mathrm{MeV}$ state.

Figure 1

${}^{10}\mathrm{Be}$ excitation energy spectrum for all $\alpha +{}^6\mathrm{He}$ coincident events. The dotted line indicates the experimental detection efficiency. In the inset the states are shown fitted with Gaussian line shapes (dotted lines) above a smoothly varying background (dashed line). The overall fit is given by the smooth solid line.

Figure 2

${}^{10}\mathrm{Be}$ excitation energy spectrum for the out-of-plane detector pair only. The energies of all states listed by Fletcher et al. [9] are indicated by the vertical solid lines. The vertical dotted lines highlight the states in ${}^{10}\mathrm{Be}$ that decay to $\alpha +{}^6\mathrm{He}_{\mathrm{g.s.}}$.

Figure 3

Experimental (data points) and fitted (solid line) correlation functions for the state at $10.15\mathrm{MeV}$ in ${}^{10}\mathrm{Be}$. A value of $J=3$ was assumed in the fit. The Monte Carlo efficiency curve used to correct $N\left(\psi \right)$ is shown by the dotted line.

Figure 4

Experimental (data points) and fitted (solid and dashed lines, see text) correlation functions for the state at $11.76\mathrm{MeV}$ in ${}^{10}\mathrm{Be}$. $\mathrm{A}$ value of (a) $J=4$ and (b) $J=5$ was assumed in the fit.

Figure 5

(a) Experimental (data points) and fitted (solid line) correlation functions for the state at $11.76\mathrm{MeV}$ in ${}^{10}\mathrm{Be}$. A value of $J=6$ was assumed in the fit. The Monte Carlo efficiency curve used to correct $N\left(\psi \right)$ is shown by the dotted line. (b) Experimental correlation function for the excitation energy region $12.3–13.0\mathrm{MeV}$ in ${}^{10}\mathrm{Be}$. The solid line is to guide the eye.