Electromagnetic transition from the 4${}^{+}$ to 2${}^{+}$ resonance in ${}^8$Be measured via the radiative capture in ${}^4$He+${}^4$He

Abstract

An earlier measurement on the 4${}^{+}$ to 2${}^{+}$ radiative transition in ${}^8$Be provided the first electromagnetic signature of its dumbbell-like shape. However, the large uncertainty in the measured cross section does not allow a stringent test of nuclear structure models. The present paper reports a more elaborate and precise measurement for this transition, via the radiative capture in the ${}^4$He+${}^4$He reaction, improving the accuracy by about a factor of three. The {\it ab initio} calculations of the radiative transition strength with improved three-nucleon forces are also presented. The experimental results are compared with the predictions of the alpha cluster model and {\it ab initio} calculations.

5 pages and 7 figures, Submitted to Physical Review Letters