In order to test { \it ab-initio} calculations of light nuclei, we have remeasured lifetimes in $^{ 10}$Be using the Doppler Shift Attenuation Method (DSAM) following the $^{ 7}$Li($^7$Li,$\alpha$)$^{ 10}$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)$_{ stat}\pm$(7)$_{ sys}$ fs corresponding to a $B$($E2\downarrow$) of 9.2(3) $e^2$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) $e^2$fm$^4$ and provides a more discriminating test of nuclear models. New Green's Function Monte Carlo (GFMC) calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.
Categories: nucl-ex