The flux of ^ { 7 } Be and ^ { 8 } B neutrinos from the Sun and the production of ^ { 7 } Li via primordial nucleosynthesis depend on the rate of the ^ { 3 } He ( \alpha , \gamma ) ^ { 7 } Be reaction .
In extension of a previous study showing cross section data at 127 - 167 keV center of mass energy , the present work reports on a measurement of the ^ { 3 } He ( \alpha , \gamma ) ^ { 7 } Be cross section at 106 keV performed at Italy ’ s Gran Sasso underground laboratory by the activation method .
This energy is closer to the solar Gamow energy than ever reached before .
The result is \sigma = 0.567 \pm 0.029 _ { stat } \pm 0.016 _ { syst } nbarn .
The data are compared with previous activation studies at high energy , and a recommended S ( 0 ) value for all ^ { 3 } He ( \alpha , \gamma ) ^ { 7 } Be activation studies , including the present work , is given .