New precision measurement of the 3He(4He,gamma) 7Be cross section.

The 3He(4He,gamma) 7Be reaction plays an important role in determining the high energy solar neutrino flux and in understanding the abundances of primordial 7Li. This Letter reports a new precision measurement of the cross sections of this direct capture reaction, determined by measuring the ensuing 7Be activity in the region of Ec.m.=420 to 950 keV. Various recent theoretical fits to our data result in a consistent extrapolated value of S34(0)=0.53(2)(1) keV b.