Precise Electromagnetic Tests of Ab Initio Calculations of Light Nuclei: States in ${}^{10}\mathrm{Be}$

In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in ${}^{10}\mathrm{Be}$ using the Doppler shift attenuation method (DSAM) following the ${}^7\mathrm{Li}({}^7\mathrm{Li},\alpha ){}^{10}\mathrm{Be}$ reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The $J^{\pi }=2_1^{+}$ state at 3.37 MeV has $\tau =205\pm (5{)}_{\mathrm{stat}}\pm (7{)}_{\mathrm{sys}}\mathrm{fs}$ corresponding to a $B(E2\downarrow )$ of $9.2(3)e^2{\mathrm{fm}}^4$ in broad agreement with many calculations. The $J^{\pi }=2_2^{+}$ state at 5.96 MeV was found to have a $B(E2\downarrow )$ of $0.11(2)e^2{\mathrm{fm}}^4$ and provides a more discriminating test of nuclear models. New Green’s function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.

Figure 1

(Top and middle) Spectra gated on ${}^{10}\mathrm{Be}$ recoil groups with the $\gamma$-ray transitions labeled by the decaying state. (Bottom) Energy loss versus total energy from the ionization chamber behind the focal plane of the FMA. The circled regions correspond to direct population of distinct ${}^{10}\mathrm{Be}$ levels. The top panel inset shows a level scheme for the five bound excited states in ${}^{10}\mathrm{Be}$ with $\gamma$-ray energies in MeV.

Figure 2

(a) Measured centroid of the 3.37-MeV transition for each of the Gammasphere angle groups compared to a fit with the relativistic Doppler formula (solid line) and to the maximum velocity (dashed line). (b) Similar to (a) but normalized to the best fit function with $\beta =0.05109(19)$.